AKModel/migrations/0061_types.py

+# Generated by Django 4.2.13 on 2025-02-25 20:58
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('AKModel', '0060_orga_message_resolved'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='AKType',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(help_text='Name describing the type', max_length=128, verbose_name='Name')),
+                ('event', models.ForeignKey(help_text='Associated event', on_delete=django.db.models.deletion.CASCADE, to='AKModel.event', verbose_name='Event')),
+            ],
+            options={
+                'verbose_name': 'AK Type',
+                'verbose_name_plural': 'AK Types',
+                'ordering': ['name'],
+                'unique_together': {('event', 'name')},
+            },
+        ),
+        migrations.AddField(
+            model_name='ak',
+            name='types',
+            field=models.ManyToManyField(blank=True, help_text='This AK is', to='AKModel.aktype', verbose_name='Types'),
+        ),
+    ]

AKModel/migrations/0062_interest_no_history.py

+# Generated by Django 4.2.13 on 2025-02-26 22:35
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('AKModel', '0061_types'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='historicalak',
+            name='interest',
+        ),
+    ]

AKModel/migrations/0063_field_validators.py

+# Generated by Django 4.2.13 on 2025-03-03 19:59
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('AKModel', '0062_interest_no_history'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='ak',
+            name='name',
+            field=models.CharField(help_text='Name of the AK', max_length=256, validators=[django.core.validators.RegexValidator(inverse_match=True, message='May not contain quotation marks', regex='[\'\\"´`]+'), django.core.validators.RegexValidator(message='Must contain at least one letter or digit', regex='[\\w\\s]+')], verbose_name='Name'),
+        ),
+        migrations.AlterField(
+            model_name='ak',
+            name='short_name',
+            field=models.CharField(blank=True, help_text='Name displayed in the schedule', max_length=64, validators=[django.core.validators.RegexValidator(inverse_match=True, message='May not contain quotation marks', regex='[\'\\"´`]+')], verbose_name='Short Name'),
+        ),
+        migrations.AlterField(
+            model_name='akowner',
+            name='name',
+            field=models.CharField(help_text='Name to identify an AK owner by', max_length=64, validators=[django.core.validators.RegexValidator(inverse_match=True, message='May not contain quotation marks', regex='[\'\\"´`]+'), django.core.validators.RegexValidator(message='Must contain at least one letter or digit', regex='[\\w\\s]+')], verbose_name='Nickname'),
+        ),
+        migrations.AlterField(
+            model_name='historicalak',
+            name='name',
+            field=models.CharField(help_text='Name of the AK', max_length=256, validators=[django.core.validators.RegexValidator(inverse_match=True, message='May not contain quotation marks', regex='[\'\\"´`]+'), django.core.validators.RegexValidator(message='Must contain at least one letter or digit', regex='[\\w\\s]+')], verbose_name='Name'),
+        ),
+        migrations.AlterField(
+            model_name='historicalak',
+            name='short_name',
+            field=models.CharField(blank=True, help_text='Name displayed in the schedule', max_length=64, validators=[django.core.validators.RegexValidator(inverse_match=True, message='May not contain quotation marks', regex='[\'\\"´`]+')], verbose_name='Short Name'),
+        ),
+    ]

AKModel/migrations/0064_event_export_slot.py

+# Generated by Django 5.1.6 on 2025-03-29 22:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("AKModel", "0063_field_validators"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="event",
+            name="export_slot",
+            field=models.DecimalField(
+                decimal_places=2,
+                default=1,
+                help_text="Slot duration in hours that is used in the timeslot discretization, when this event is exported for the solver.",
+                max_digits=4,
+                verbose_name="Export Slot Length",
+            ),
+        ),
+    ]

AKModel/migrations/0065_eventparticipant_akpreference_and_more.py

+# Generated by Django 4.2.13 on 2025-02-10 10:23
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("AKModel", "0064_event_export_slot"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="EventParticipant",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                (
+                    "name",
+                    models.CharField(
+                        blank=True,
+                        help_text="Name to identify a participant by (in case of questions from the organizers)",
+                        max_length=64,
+                        verbose_name="Nickname",
+                    ),
+                ),
+                (
+                    "institution",
+                    models.CharField(
+                        blank=True,
+                        help_text="Uni etc.",
+                        max_length=128,
+                        verbose_name="Institution",
+                    ),
+                ),
+                (
+                    "event",
+                    models.ForeignKey(
+                        help_text="Associated event",
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="AKModel.event",
+                        verbose_name="Event",
+                    ),
+                ),
+            ],
+            options={
+                "verbose_name": "Participant",
+                "verbose_name_plural": "Participants",
+                "ordering": ["name"],
+            },
+        ),
+        migrations.CreateModel(
+            name="AKPreference",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                (
+                    "preference",
+                    models.PositiveSmallIntegerField(
+                        choices=[
+                            (0, "Ignore"),
+                            (1, "Prefer"),
+                            (2, "Strong prefer"),
+                            (3, "Required"),
+                        ],
+                        default=0,
+                        help_text="Preference level for the AK",
+                        verbose_name="Preference",
+                    ),
+                ),
+                (
+                    "ak",
+                    models.ForeignKey(
+                        help_text="AK this preference belongs to",
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="AKModel.ak",
+                        verbose_name="AK",
+                    ),
+                ),
+                (
+                    "event",
+                    models.ForeignKey(
+                        help_text="Associated event",
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="AKModel.event",
+                        verbose_name="Event",
+                    ),
+                ),
+                (
+                    "participant",
+                    models.ForeignKey(
+                        help_text="Participant this preference belongs to",
+                        on_delete=django.db.models.deletion.CASCADE,
+                        to="AKModel.eventparticipant",
+                        verbose_name="Participant",
+                    ),
+                ),
+            ],
+            options={
+                "verbose_name": "AK Preference",
+                "verbose_name_plural": "AK Preferences",
+            },
+        ),
+        migrations.AddField(
+            model_name="availability",
+            name="participant",
+            field=models.ForeignKey(
+                blank=True,
+                help_text="Participant whose availability this is",
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                related_name="availabilities",
+                to="AKModel.eventparticipant",
+                verbose_name="Participant",
+            ),
+        ),
+    ]

AKModel/migrations/0066_akpreference_slot_alter_akpreference_unique_together_and_more.py

+# Generated by Django 4.2.13 on 2025-02-10 22:31
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("AKModel", "0065_eventparticipant_akpreference_and_more"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="akpreference",
+            name="slot",
+            field=models.ForeignKey(
+                default=None,
+                help_text="AKSlot this preference belongs to",
+                on_delete=django.db.models.deletion.CASCADE,
+                to="AKModel.akslot",
+                verbose_name="AKSlot",
+            ),
+            preserve_default=False,
+        ),
+        migrations.AlterUniqueTogether(
+            name="akpreference",
+            unique_together={("event", "participant", "slot")},
+        ),
+        migrations.RemoveField(
+            model_name="akpreference",
+            name="ak",
+        ),
+    ]

AKModel/migrations/0067_eventparticipant_requirements_and_more.py

+# Generated by Django 4.2.13 on 2025-02-11 00:23
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        (
+            "AKModel",
+            "0066_akpreference_slot_alter_akpreference_unique_together_and_more",
+        ),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="eventparticipant",
+            name="requirements",
+            field=models.ManyToManyField(
+                blank=True,
+                help_text="Participant's Requirements",
+                to="AKModel.akrequirement",
+                verbose_name="Requirements",
+            ),
+        ),
+        migrations.AlterField(
+            model_name="akpreference",
+            name="slot",
+            field=models.ForeignKey(
+                help_text="AK Slot this preference belongs to",
+                on_delete=django.db.models.deletion.CASCADE,
+                to="AKModel.akslot",
+                verbose_name="AK Slot",
+            ),
+        ),
+    ]

AKModel/models.py

-# Create your models here.
+import decimal
+import itertools
+import json
+import math
+from dataclasses import dataclass
+from datetime import datetime, timedelta
+from typing import Any, Generator, Iterable
+
+from django.apps import apps
+from django.core.validators import RegexValidator
+from django.db import models, transaction
+from django.db.models import Count
+from django.urls import reverse_lazy
+from django.utils import timezone
+from django.utils.text import slugify
+from django.utils.translation import gettext_lazy as _
+from simple_history.models import HistoricalRecords
+from timezone_field import TimeZoneField
+
+# Custom validators to be used for some of the fields
+# Prevent inclusion of the quotation marks ' " ´ `
+# This may be necessary to prevent javascript issues
+no_quotation_marks_validator = RegexValidator(regex=r"['\"´`]+", inverse_match=True,
+                                              message=_('May not contain quotation marks'))
+# Enforce that the field contains of at least one letter or digit (and not just special characters
+# This prevents issues when autogenerating slugs from that field
+slugable_validator = RegexValidator(regex=r"[\w\s]+", message=_('Must contain at least one letter or digit'))
+
+
+@dataclass
+class OptimizerTimeslot:
+    """Class describing a discrete timeslot. Used to interface with an optimizer."""
+
+    avail: "Availability"
+    """The availability object corresponding to this timeslot."""
+
+    idx: int
+    """The unique index of this optimizer timeslot."""
+
+    constraints: set[str]
+    """The set of time constraints fulfilled by this object."""
+
+    def merge(self, other: "OptimizerTimeslot") -> "OptimizerTimeslot":
+        """Merge with other OptimizerTimeslot.
+
+        Creates a new OptimizerTimeslot object.
+        Its availability is constructed by merging the availabilities of self and other,
+        its constraints by taking the union of both constraint sets.
+        As an index, the index of self is used.
+        """
+        avail = self.avail.merge_with(other.avail)
+        constraints = self.constraints.union(other.constraints)
+        return OptimizerTimeslot(
+            avail=avail, idx=self.idx, constraints=constraints
+        )
+
+    def __repr__(self) -> str:
+        return f"({self.avail.simplified}, {self.idx}, {self.constraints})"
+
+TimeslotBlock = list[OptimizerTimeslot]
+
+
+def merge_blocks(
+    blocks: Iterable[TimeslotBlock]
+) -> Iterable[TimeslotBlock]:
+    """Merge iterable of blocks together.
+
+    The timeslots of all blocks are grouped into maximal blocks.
+    Timeslots with the same start and end are identified with each other
+    and merged (cf `OptimizerTimeslot.merge`).
+    Throws a ValueError if any timeslots are overlapping but do not
+    share the same start and end, i.e. partial overlap is not allowed.
+
+    :param blocks: iterable of blocks to merge.
+    :return: iterable of merged blocks.
+    :rtype: iterable over lists of OptimizerTimeslot objects
+    """
+    if not blocks:
+        return []
+
+    # flatten timeslot iterables to single chain
+    timeslot_chain = itertools.chain.from_iterable(blocks)
+
+    # sort timeslots according to start
+    timeslots = sorted(
+        timeslot_chain,
+        key=lambda slot: slot.avail.start
+    )
+
+    if not timeslots:
+        return []
+
+    all_blocks = []
+    current_block = [timeslots[0]]
+    timeslots = timeslots[1:]
+
+    for slot in timeslots:
+        if current_block and slot.avail.overlaps(current_block[-1].avail, strict=True):
+            if (
+                slot.avail.start == current_block[-1].avail.start
+                and slot.avail.end == current_block[-1].avail.end
+            ):
+                # the same timeslot -> merge
+                current_block[-1] = current_block[-1].merge(slot)
+            else:
+                # partial overlap of interiors -> not supported
+                raise ValueError(
+                    "Partially overlapping timeslots are not supported!"
+                    f" ({current_block[-1].avail.simplified}, {slot.avail.simplified})"
+                )
+        elif not current_block or slot.avail.overlaps(current_block[-1].avail, strict=False):
+            # only endpoints in intersection -> same block
+            current_block.append(slot)
+        else:
+            # no overlap at all -> new block
+            all_blocks.append(current_block)
+            current_block = [slot]
+
+    if current_block:
+        all_blocks.append(current_block)
+
+    return all_blocks
+
+
+class Event(models.Model):
+    """
+    An event supplies the frame for all Aks.
+    """
+    name = models.CharField(max_length=64, unique=True, verbose_name=_('Name'),
+                            help_text=_('Name or iteration of the event'))
+    slug = models.SlugField(max_length=32, unique=True, verbose_name=_('Short Form'),
+                            help_text=_('Short name of letters/numbers/dots/dashes/underscores used in URLs.'))
+
+    place = models.CharField(max_length=128, blank=True, verbose_name=_('Place'),
+                             help_text=_('City etc. the event takes place in'))
+    timezone = TimeZoneField(default='Europe/Berlin', blank=False, choices_display="WITH_GMT_OFFSET",
+                             verbose_name=_('Time Zone'), help_text=_('Time Zone where this event takes place in'))
+    start = models.DateTimeField(verbose_name=_('Start'), help_text=_('Time the event begins'))
+    end = models.DateTimeField(verbose_name=_('End'), help_text=_('Time the event ends'))
+    reso_deadline = models.DateTimeField(verbose_name=_('Resolution Deadline'), blank=True, null=True,
+                                         help_text=_('When should AKs with intention to submit a resolution be done?'))
+
+    interest_start = models.DateTimeField(verbose_name=_('Interest Window Start'), blank=True, null=True,
+                                          help_text=
+                                          _('Opening time for expression of interest. When left blank, no interest '
+                                            'indication will be possible.'))
+
+    interest_end = models.DateTimeField(verbose_name=_('Interest Window End'), blank=True, null=True,
+                                        help_text=_('Closing time for expression of interest.'))
+
+    public = models.BooleanField(verbose_name=_('Public event'), default=True,
+                                 help_text=_('Show this event on overview page.'))
+
+    active = models.BooleanField(verbose_name=_('Active State'), help_text=_('Marks currently active events'))
+    plan_hidden = models.BooleanField(verbose_name=_('Plan Hidden'), help_text=_('Hides plan for non-staff users'),
+                                      default=True)
+    plan_published_at = models.DateTimeField(verbose_name=_('Plan published at'), blank=True, null=True,
+                                             help_text=_('Timestamp at which the plan was published'))
+
+    base_url = models.URLField(verbose_name=_("Base URL"), help_text=_("Prefix for wiki link construction"), blank=True)
+    wiki_export_template_name = models.CharField(verbose_name=_("Wiki Export Template Name"), blank=True, max_length=50)
+    default_slot = models.DecimalField(max_digits=4, decimal_places=2, default=2, verbose_name=_('Default Slot Length'),
+                                       help_text=_('Default length in hours that is assumed for AKs in this event.'))
+    export_slot = models.DecimalField(max_digits=4, decimal_places=2, default=1, verbose_name=_('Export Slot Length'),
+                                        help_text=_(
+                                            'Slot duration in hours that is used in the timeslot discretization, '
+                                            'when this event is exported for the solver.'
+                                        ))
+
+
+    contact_email = models.EmailField(verbose_name=_("Contact email address"), blank=True,
+                                      help_text=_("An email address that is displayed on every page "
+                                                  "and can be used for all kinds of questions"))
+
+    class Meta:
+        verbose_name = _('Event')
+        verbose_name_plural = _('Events')
+        ordering = ['-start']
+
+    def __str__(self):
+        return self.name
+
+    @staticmethod
+    def get_by_slug(slug):
+        """
+        Get event by its slug
+
+        :param slug: slug of the event
+        :return: event identified by the slug
+        :rtype: Event
+        """
+        return Event.objects.get(slug=slug)
+
+    @staticmethod
+    def get_next_active():
+        """
+        Get first active event taking place
+        :return: matching event (if any) or None
+        :rtype: Event
+        """
+        event = Event.objects.filter(active=True).order_by('start').first()
+        # No active event? Return the next event taking place
+        if event is None:
+            event = Event.objects.order_by('start').filter(start__gt=datetime.now().astimezone()).first()
+        return event
+
+    def get_categories_with_aks(self, wishes_seperately=False,
+                                filter_func=lambda ak: True, hide_empty_categories=False):
+        """
+        Get AKCategories as well as a list of AKs belonging to the category for this event
+
+        :param wishes_seperately: Return wishes as individual list.
+        :type wishes_seperately: bool
+        :param filter_func: Optional filter predicate, only include AK in list if filter returns True
+        :type filter_func: (AK)->bool
+        :return: list of category-AK-list-tuples, optionally the additional list of AK wishes
+        :rtype: list[(AKCategory, list[AK])] [, list[AK]]
+        """
+        categories = self.akcategory_set.select_related('event').all()
+        categories_with_aks = []
+        ak_wishes = []
+
+        # Fill lists by iterating
+        # A different behavior is needed depending on whether wishes should show up inside their categories
+        # or as a separate category
+
+        def _get_category_aks(category):
+            """
+            Get all AKs belonging to a category
+            Use joining and prefetching to reduce the number of necessary SQL queries
+
+            :param category: category the AKs should belong to
+            :return: QuerySet over AKs
+            :return: QuerySet[AK]
+            """
+            return category.ak_set.select_related('event').prefetch_related('owners', 'akslot_set').all()
+
+        if wishes_seperately:
+            for category in categories:
+                ak_list = []
+                for ak in _get_category_aks(category):
+                    if filter_func(ak):
+                        if ak.wish:
+                            ak_wishes.append(ak)
+                        else:
+                            ak_list.append(ak)
+                if not hide_empty_categories or len(ak_list) > 0:
+                    categories_with_aks.append((category, ak_list))
+            return categories_with_aks, ak_wishes
+
+        for category in categories:
+            ak_list = []
+            for ak in _get_category_aks(category):
+                if filter_func(ak):
+                    ak_list.append(ak)
+            if not hide_empty_categories or len(ak_list) > 0:
+                categories_with_aks.append((category, ak_list))
+        return categories_with_aks
+
+    def get_unscheduled_wish_slots(self):
+        """
+        Get all slots of wishes that are currently not scheduled
+        :return: queryset of theses slots
+        :rtype: QuerySet[AKSlot]
+        """
+        return self.akslot_set.filter(start__isnull=True).annotate(Count('ak__owners')).filter(ak__owners__count=0)
+
+    def get_aks_without_availabilities(self):
+        """
+        Gt all AKs that don't have any availability at all
+
+        :return: generator over these AKs
+        :rtype: Generator[AK]
+        """
+        return (self.ak_set
+                .annotate(Count('availabilities', distinct=True))
+                .annotate(Count('owners', distinct=True))
+                .filter(availabilities__count=0, owners__count__gt=0)
+                )
+
+    def _generate_slots_from_block(
+        self,
+        start: datetime,
+        end: datetime,
+        slot_duration: timedelta,
+        *,
+        slot_index: int = 0,
+        constraints: set[str] | None = None,
+    ) -> Generator[TimeslotBlock, None, int]:
+        """Discretize a time range into timeslots.
+
+        Uses a uniform discretization into discrete slots of length `slot_duration`,
+        starting at `start`. No incomplete timeslots are generated, i.e.
+        if (`end` - `start`) is not a whole number multiple of `slot_duration`
+        then the last incomplete timeslot is dropped.
+
+        :param start: Start of the time range.
+        :param end: Start of the time range.
+        :param slot_duration: Duration of a single timeslot in the discretization.
+        :param slot_index: index of the first timeslot. Defaults to 0.
+
+        :yield: Block of optimizer timeslots as the discretization result.
+        :ytype: list of OptimizerTimeslot
+
+        :return: The first slot index after the yielded blocks, i.e.
+            `slot_index` + total # generated timeslots
+        :rtype: int
+        """
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+
+        current_slot_start = start
+        previous_slot_start: datetime | None = None
+
+        if constraints is None:
+            constraints = set()
+
+        current_block = []
+
+        room_availabilities = list({
+            availability
+            for room in Room.objects.filter(event=self)
+            for availability in room.availabilities.all()
+        })
+
+        while current_slot_start + slot_duration <= end:
+            slot = Availability(
+                event=self,
+                start=current_slot_start,
+                end=current_slot_start + slot_duration,
+            )
+
+            if any((availability.contains(slot) for availability in room_availabilities)):
+                # no gap in a block
+                if (
+                    previous_slot_start is not None
+                    and previous_slot_start + slot_duration < current_slot_start
+                ):
+                    yield current_block
+                    current_block = []
+
+                current_block.append(
+                    OptimizerTimeslot(avail=slot, idx=slot_index, constraints=constraints)
+                )
+                previous_slot_start = current_slot_start
+
+            slot_index += 1
+            current_slot_start += slot_duration
+
+        if current_block:
+            yield current_block
+
+        return slot_index
+
+    def uniform_time_slots(self, *, slots_in_an_hour: float) -> Iterable[TimeslotBlock]:
+        """Uniformly discretize the entire event into blocks of timeslots.
+
+        Discretizes entire event uniformly. May not necessarily result in a single block
+        as slots with no room availability are dropped.
+
+        :param slots_in_an_hour: The percentage of an hour covered by a single slot.
+            Determines the discretization granularity.
+        :yield: Block of optimizer timeslots as the discretization result.
+        :ytype: list of OptimizerTimeslot
+        """
+        all_category_constraints = AKCategory.create_category_optimizer_constraints(
+            AKCategory.objects.filter(event=self).all()
+        )
+
+        yield from self._generate_slots_from_block(
+            start=self.start,
+            end=self.end,
+            slot_duration=timedelta(hours=1.0 / slots_in_an_hour),
+            constraints=all_category_constraints,
+        )
+
+    def default_time_slots(self, *, slots_in_an_hour: float) -> Iterable[TimeslotBlock]:
+        """Discretize all default slots into blocks of timeslots.
+
+        In the discretization each default slot corresponds to one block.
+
+        :param slots_in_an_hour: The percentage of an hour covered by a single slot.
+            Determines the discretization granularity.
+        :yield: Block of optimizer timeslots as the discretization result.
+        :ytype: list of TimeslotBlock
+        """
+        slot_duration = timedelta(hours=1.0 / slots_in_an_hour)
+        slot_index = 0
+
+        for block_slot in DefaultSlot.objects.filter(event=self).order_by("start", "end"):
+            category_constraints = AKCategory.create_category_optimizer_constraints(
+                block_slot.primary_categories.all()
+            )
+
+            slot_index = yield from self._generate_slots_from_block(
+                start=block_slot.start,
+                end=block_slot.end,
+                slot_duration=slot_duration,
+                slot_index=slot_index,
+                constraints=category_constraints,
+            )
+
+    def discretize_timeslots(self, *, slots_in_an_hour: float | None = None) -> Iterable[TimeslotBlock]:
+        """"Choose discretization scheme.
+
+        Uses default_time_slots if the event has any DefaultSlot, otherwise uniform_time_slots.
+
+        :param slots_in_an_hour: The percentage of an hour covered by a single slot.
+            Determines the discretization granularity.
+        :yield: Block of optimizer timeslots as the discretization result.
+        :ytype: list of TimeslotBlock
+        """
+
+        if slots_in_an_hour is None:
+            slots_in_an_hour = 1.0 / float(self.export_slot)
+
+        if DefaultSlot.objects.filter(event=self).exists():
+            # discretize default slots if they exists
+            yield from merge_blocks(self.default_time_slots(slots_in_an_hour=slots_in_an_hour))
+        else:
+            yield from self.uniform_time_slots(slots_in_an_hour=slots_in_an_hour)
+
+    @transaction.atomic
+    def schedule_from_json(
+        self, schedule: str | dict[str, Any], *, check_for_data_inconsistency: bool = True
+    ) -> int:
+        """Load AK schedule from a json string.
+
+        :param schedule: A string that can be decoded to json, describing
+            the AK schedule. The json data is assumed to be constructed
+            following the output specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        """
+        if isinstance(schedule, str):
+            schedule = json.loads(schedule)
+
+        if "input" not in schedule or "scheduled_aks" not in schedule:
+            raise ValueError(_("Cannot parse malformed JSON input."))
+
+        if check_for_data_inconsistency:
+            export_dict = self.as_json_dict()
+            if schedule["input"] != export_dict:
+                raise ValueError(_("Data has changed since the export. Reexport and run the solver again."))
+
+        slots_in_an_hour = schedule["input"]["timeslots"]["info"]["duration"]
+
+        timeslot_dict = {
+            timeslot.idx: timeslot
+            for block in self.discretize_timeslots(slots_in_an_hour=slots_in_an_hour)
+            for timeslot in block
+        }
+
+        slots_updated = 0
+        for scheduled_slot in schedule["scheduled_aks"]:
+            scheduled_slot["timeslot_ids"] = list(map(int, scheduled_slot["timeslot_ids"]))
+            slot = AKSlot.objects.get(id=int(scheduled_slot["ak_id"]))
+
+            if not scheduled_slot["timeslot_ids"]:
+                raise ValueError(
+                    _("AK {ak_name} is not assigned any timeslot by the solver").format(ak_name=slot.ak.name)
+                )
+
+            start_timeslot = timeslot_dict[min(scheduled_slot["timeslot_ids"])].avail
+            end_timeslot = timeslot_dict[max(scheduled_slot["timeslot_ids"])].avail
+            solver_duration = (end_timeslot.end - start_timeslot.start).total_seconds() / 3600.0
+
+            if solver_duration + 2e-4 < slot.duration:
+                raise ValueError(
+                    _(
+                        "Duration of AK {ak_name} assigned by solver ({solver_duration} hours) "
+                        "is less than the duration required by the slot ({slot_duration} hours)"
+                    ).format(
+                        ak_name=slot.ak.name,
+                        solver_duration=solver_duration,
+                        slot_duration=slot.duration,
+                    )
+                )
+
+            if slot.fixed:
+                solver_room = Room.objects.get(id=int(scheduled_slot["room_id"]))
+                if slot.room != solver_room:
+                    raise ValueError(
+                        _(
+                            "Fixed AK {ak_name} assigned by solver to room {solver_room} "
+                            "is fixed to room {slot_room}"
+                        ).format(
+                            ak_name=slot.ak.name,
+                            solver_room=solver_room.name,
+                            slot_room=slot.room.name,
+                        )
+                    )
+                if slot.start != start_timeslot.start:
+                    raise ValueError(
+                        _(
+                            "Fixed AK {ak_name} assigned by solver to start at {solver_start} "
+                            "is fixed to start at {slot_start}"
+                        ).format(
+                            ak_name=slot.ak.name,
+                            solver_start=start_timeslot.start,
+                            slot_start=slot.start,
+                        )
+                    )
+            else:
+                slot.room = Room.objects.get(id=int(scheduled_slot["room_id"]))
+                slot.start = start_timeslot.start
+                slot.save()
+                slots_updated += 1
+
+        return slots_updated
+
+    def as_json_dict(self) -> dict[str, Any]:
+        """Return the json representation of this Event.
+
+        :return: The json dict representation is constructed
+            following the input specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        :rtype: dict[str, Any]
+        """
+
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+
+        def _check_event_not_covered(availabilities: list[Availability]) -> bool:
+            """Test if event is not covered by availabilities."""
+            return not Availability.is_event_covered(self, availabilities)
+
+        def _check_akslot_fixed_in_timeslot(ak_slot: AKSlot, timeslot: Availability) -> bool:
+            """Test if an AKSlot is fixed to overlap a timeslot slot."""
+            if not ak_slot.fixed or ak_slot.start is None:
+                return False
+
+            fixed_avail = Availability(event=self, start=ak_slot.start, end=ak_slot.end)
+            return fixed_avail.overlaps(timeslot, strict=True)
+
+        def _check_add_constraint(slot: Availability, availabilities: list[Availability]) -> bool:
+            """Test if object is not available for whole event and may happen during slot."""
+            return (
+                _check_event_not_covered(availabilities) and slot.is_covered(availabilities)
+            )
+
+        def _generate_time_constraints(
+            avail_label: str,
+            avail_dict: dict,
+            timeslot_avail: Availability,
+            prefix: str = "availability",
+        ) -> list[str]:
+            return [
+                f"{prefix}-{avail_label}-{pk}"
+                for pk, availabilities in avail_dict.items()
+                if _check_add_constraint(timeslot_avail, availabilities)
+            ]
+
+        timeslots = {
+            "info": {"duration": float(self.export_slot)},
+            "blocks": [],
+            }
+
+        rooms = Room.objects.filter(event=self).order_by()
+        slots = AKSlot.objects.filter(event=self).order_by()
+        participants = EventParticipant.objects.filter(event=self).order_by()
+        owners = AKOwner.objects.filter(event=self).order_by().all()
+
+        ak_availabilities = {
+            ak.pk: Availability.union(ak.availabilities.all())
+            for ak in AK.objects.filter(event=self).all()
+        }
+        room_availabilities = {
+            room.pk: Availability.union(room.availabilities.all())
+            for room in rooms
+        }
+        person_availabilities = {
+            person.pk: Availability.union(person.availabilities.all())
+            for person in owners
+        }
+        participant_availabilities = {
+            participant.pk: Availability.union(participant.availabilities.all())
+            for participant in EventParticipant.objects.filter(event=self)
+        }
+
+        blocks = list(self.discretize_timeslots())
+
+        block_names = []
+
+        for block_idx, block in enumerate(blocks):
+            current_block = []
+
+            if not block:
+                continue
+
+            block_start = block[0].avail.start.astimezone(self.timezone)
+            block_end = block[-1].avail.end.astimezone(self.timezone)
+
+            start_day = block_start.strftime("%A, %d. %b")
+            if block_start.date() == block_end.date():
+                # same day
+                time_str = block_start.strftime("%H:%M") + " - " + block_end.strftime("%H:%M")
+            else:
+                # different days
+                time_str = block_start.strftime("%a %H:%M") + " - " + block_end.strftime("%a %H:%M")
+            block_names.append([start_day, time_str])
+
+            block_timeconstraints = [f"notblock{idx}" for idx in range(len(blocks)) if idx != block_idx]
+
+            for timeslot in block:
+                time_constraints = []
+                # if reso_deadline is set and timeslot ends before it,
+                #   add fulfilled time constraint 'resolution'
+                if self.reso_deadline is None or timeslot.avail.end < self.reso_deadline:
+                    time_constraints.append("resolution")
+
+                # add fulfilled time constraints for all AKs that cannot happen during full event
+                time_constraints.extend(
+                    _generate_time_constraints("ak", ak_availabilities, timeslot.avail)
+                )
+
+                # add fulfilled time constraints for all persons that are not available for full event
+                time_constraints.extend(
+                    _generate_time_constraints("person", person_availabilities, timeslot.avail)
+                )
+
+                # add fulfilled time constraints for all rooms that are not available for full event
+                time_constraints.extend(
+                    _generate_time_constraints("room", room_availabilities, timeslot.avail)
+                )
+
+                # add fulfilled time constraints for all participants that are not available for full event
+                time_constraints.extend(
+                    _generate_time_constraints("participant", participant_availabilities, timeslot.avail)
+                )
+
+                # add fulfilled time constraints for all AKSlots fixed to happen during timeslot
+                time_constraints.extend([
+                    f"fixed-akslot-{slot.id}"
+                    for slot in AKSlot.objects.filter(event=self, fixed=True).exclude(start__isnull=True)
+                    if _check_akslot_fixed_in_timeslot(slot, timeslot.avail)
+                ])
+
+                time_constraints.extend(timeslot.constraints)
+                time_constraints.extend(block_timeconstraints)
+                time_constraints.sort()
+
+                current_block.append({
+                    "id": timeslot.idx,
+                    "info": {
+                        "start": timeslot.avail.start.astimezone(self.timezone).strftime("%Y-%m-%d %H:%M"),
+                        "end": timeslot.avail.end.astimezone(self.timezone).strftime("%Y-%m-%d %H:%M"),
+                    },
+                    "fulfilled_time_constraints": time_constraints,
+                    })
+
+            timeslots["blocks"].append(current_block)
+
+        timeslots["info"]["blocknames"] = block_names
+
+        info_dict = {
+            "title": self.name,
+            "slug": self.slug
+        }
+
+        for attr in ["contact_email", "place"]:
+            if hasattr(self, attr) and getattr(self, attr):
+                info_dict[attr] = getattr(self, attr)
+
+        data = {
+            "participants": [p.as_json_dict() for p in participants],
+            "rooms": [r.as_json_dict() for r in rooms],
+            "timeslots": timeslots,
+            "info": info_dict,
+            "aks": [ak.as_json_dict() for ak in slots],
+        }
+
+        if EventParticipant.objects.exists():
+            next_participant_pk = EventParticipant.objects.latest("pk").pk + 1
+        else:
+            next_participant_pk = 1
+        # add one dummy participant per owner
+        # this ensures that the hard constraints from each owner are considered
+        for new_pk, owner in enumerate(owners, next_participant_pk):
+            owned_slots = slots.filter(ak__owners=owner).order_by().all()
+            if not owned_slots:
+                continue
+            new_participant_data = {
+                "id": new_pk,
+                "info": {"name": f"{owner} [AKOwner]"},
+                "room_constraints": [],
+                "time_constraints": [],
+                "preferences": [
+                    {"ak_id": slot.pk, "required": True, "preference_score": -1}
+                    for slot in owned_slots
+                ]
+            }
+            data["participants"].append(new_participant_data)
+        return data
+
+
+class AKOwner(models.Model):
+    """ An AKOwner describes the person organizing/holding an AK.
+    """
+    name = models.CharField(max_length=64, verbose_name=_('Nickname'),
+                            validators=[no_quotation_marks_validator, slugable_validator],
+                            help_text=_('Name to identify an AK owner by'))
+    slug = models.SlugField(max_length=64, blank=True, verbose_name=_('Slug'), help_text=_('Slug for URL generation'))
+    institution = models.CharField(max_length=128, blank=True, verbose_name=_('Institution'), help_text=_('Uni etc.'))
+    link = models.URLField(blank=True, verbose_name=_('Web Link'), help_text=_('Link to Homepage'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('AK Owner')
+        verbose_name_plural = _('AK Owners')
+        ordering = ['name']
+        unique_together = [['event', 'name', 'institution'], ['event', 'slug']]
+
+    def __str__(self):
+        if self.institution:
+            return f"{self.name} ({self.institution})"
+        return self.name
+
+    def _generate_slug(self):
+        """
+        Auto-generate a slug for an owner
+        This will start with a very simple slug (the name truncated to a maximum length) and then gradually produce
+        more complicated slugs when the previous candidates are already used
+
+        :return: the slug
+        :rtype: str
+        """
+        max_length = self._meta.get_field('slug').max_length
+
+        # Try name alone (truncated if necessary)
+        slug_candidate = slugify(self.name)[:max_length]
+        if not AKOwner.objects.filter(event=self.event, slug=slug_candidate).exists():
+            self.slug = slug_candidate
+            return
+
+        # Try name and institution separated by '_' (truncated if necessary)
+        slug_candidate = slugify(slug_candidate + '_' + self.institution)[:max_length]
+        if not AKOwner.objects.filter(event=self.event, slug=slug_candidate).exists():
+            self.slug = slug_candidate
+            return
+
+        # Try name + institution + an incrementing digit
+        for i in itertools.count(1):
+            if not AKOwner.objects.filter(event=self.event, slug=slug_candidate).exists():
+                break
+            digits = len(str(i))
+            slug_candidate = f'{slug_candidate[:-(digits + 1)]}-{i}'
+
+        self.slug = slug_candidate
+
+    def save(self, *args, **kwargs):
+        if not self.slug:
+            self._generate_slug()
+
+        super().save(*args, **kwargs)
+
+    @staticmethod
+    def get_by_slug(event, slug):
+        """
+        Get owner by slug
+        Will be identified by the combination of event slug and owner slug which is unique
+
+        :param event: event
+        :param slug: slug of the owner
+        :return: owner identified by slugs
+        :rtype: AKOwner
+        """
+        return AKOwner.objects.get(event=event, slug=slug)
+
+
+class AKCategory(models.Model):
+    """ An AKCategory describes the characteristics of an AK, e.g. content vs. recreational.
+    """
+    name = models.CharField(max_length=64, verbose_name=_('Name'), help_text=_('Name of the AK Category'))
+    color = models.CharField(max_length=7, blank=True, verbose_name=_('Color'), help_text=_('Color for displaying'))
+    description = models.TextField(blank=True, verbose_name=_("Description"),
+                                   help_text=_("Short description of this AK Category"))
+    present_by_default = models.BooleanField(blank=True, default=True, verbose_name=_("Present by default"),
+                                             help_text=_("Present AKs of this category by default if AK owner did not "
+                                                         "specify whether this AK should be presented?"))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('AK Category')
+        verbose_name_plural = _('AK Categories')
+        ordering = ['name']
+        unique_together = ['event', 'name']
+
+    def __str__(self):
+        return self.name
+
+    @staticmethod
+    def create_category_optimizer_constraints(categories: Iterable["AKCategory"]) -> set[str]:
+        """Create a set of constraint strings from an AKCategory iterable.
+
+        :param categories: The iterable of categories to derive the constraint strings from.
+        :return: A set of category constraint strings, i.e. strings of the form
+            'availability-cat-<cat.name>'.
+        :rtype: set of strings.
+        """
+        return {
+            f"availability-cat-{cat.name}"
+            for cat in categories
+        }
+
+
+class AKTrack(models.Model):
+    """ An AKTrack describes a set of semantically related AKs.
+    """
+    name = models.CharField(max_length=64, verbose_name=_('Name'), help_text=_('Name of the AK Track'))
+    color = models.CharField(max_length=7, blank=True, verbose_name=_('Color'), help_text=_('Color for displaying'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('AK Track')
+        verbose_name_plural = _('AK Tracks')
+        ordering = ['name']
+        unique_together = ['event', 'name']
+
+    def __str__(self):
+        return self.name
+
+    def aks_with_category(self):
+        """
+        Get all AKs that belong to this track with category already joined to prevent additional SQL queries
+        :return: queryset over the AKs
+        :rtype: QuerySet[AK]
+        """
+        return self.ak_set.select_related('category').all()
+
+
+class AKRequirement(models.Model):
+    """ An AKRequirement describes something needed to hold an AK, e.g. infrastructure.
+    """
+    name = models.CharField(max_length=128, verbose_name=_('Name'), help_text=_('Name of the Requirement'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('AK Requirement')
+        verbose_name_plural = _('AK Requirements')
+        ordering = ['name']
+        unique_together = ['event', 'name']
+
+    def __str__(self):
+        return self.name
+
+
+class AKType(models.Model):
+    """ An AKType allows to associate one or multiple types with an AK, e.g., to better describe the format of that AK
+    or to which group of people it is addressed. Types are specified per event and are an optional feature.
+    """
+    name = models.CharField(max_length=128, verbose_name=_('Name'), help_text=_('Name describing the type'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('AK Type')
+        verbose_name_plural = _('AK Types')
+        ordering = ['name']
+        unique_together = ['event', 'name']
+
+    def __str__(self):
+        return self.name
+
+
+class AK(models.Model):
+    """ An AK is a slot-based activity to be scheduled during an event.
+    """
+    name = models.CharField(max_length=256, verbose_name=_('Name'), help_text=_('Name of the AK'),
+                            validators=[no_quotation_marks_validator, slugable_validator])
+    short_name = models.CharField(max_length=64, blank=True, verbose_name=_('Short Name'),
+                                  validators=[no_quotation_marks_validator],
+                                  help_text=_('Name displayed in the schedule'))
+    description = models.TextField(blank=True, verbose_name=_('Description'), help_text=_('Description of the AK'))
+
+    owners = models.ManyToManyField(to=AKOwner, blank=True, verbose_name=_('Owners'),
+                                    help_text=_('Those organizing the AK'))
+
+    # Will be automatically generated in save method if not set
+    link = models.URLField(blank=True, verbose_name=_('Web Link'), help_text=_('Link to wiki page'))
+    protocol_link = models.URLField(blank=True, verbose_name=_('Protocol Link'), help_text=_('Link to protocol'))
+
+    category = models.ForeignKey(to=AKCategory, on_delete=models.PROTECT, verbose_name=_('Category'),
+                                 help_text=_('Category of the AK'))
+    types = models.ManyToManyField(to=AKType, blank=True, verbose_name=_('Types'),
+                                   help_text=_("This AK is"))
+    track = models.ForeignKey(to=AKTrack, blank=True, on_delete=models.SET_NULL, null=True, verbose_name=_('Track'),
+                              help_text=_('Track the AK belongs to'))
+
+    reso = models.BooleanField(verbose_name=_('Resolution Intention'), default=False,
+                               help_text=_('Intends to submit a resolution'))
+    present = models.BooleanField(verbose_name=_("Present this AK"), null=True,
+                                  help_text=_("Present results of this AK"))
+
+    requirements = models.ManyToManyField(to=AKRequirement, blank=True, verbose_name=_('Requirements'),
+                                          help_text=_("AK's Requirements"))
+
+    conflicts = models.ManyToManyField(to='AK', blank=True, related_name='conflict', verbose_name=_('Conflicting AKs'),
+                                       help_text=_('AKs that conflict and thus must not take place at the same time'))
+    prerequisites = models.ManyToManyField(to='AK', blank=True, verbose_name=_('Prerequisite AKs'),
+                                           help_text=_('AKs that should precede this AK in the schedule'))
+
+    notes = models.TextField(blank=True, verbose_name=_('Organizational Notes'), help_text=_(
+            'Notes to organizers. These are public. For private notes, please use the button for private messages '
+            'on the detail page of this AK (after creation/editing).'))
+
+    interest = models.IntegerField(default=-1, verbose_name=_('Interest'), help_text=_('Expected number of people'))
+    interest_counter = models.IntegerField(default=0, verbose_name=_('Interest Counter'),
+                                           help_text=_('People who have indicated interest online'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    include_in_export = models.BooleanField(default=True, verbose_name=_('Export?'),
+                                            help_text=_("Include AK in wiki export?"))
+
+    history = HistoricalRecords(excluded_fields=['interest', 'interest_counter', 'include_in_export'])
+
+    class Meta:
+        verbose_name = _('AK')
+        verbose_name_plural = _('AKs')
+        unique_together = [['event', 'name'], ['event', 'short_name']]
+        ordering = ['pk']
+
+    def __str__(self):
+        if self.short_name:
+            return self.short_name
+        return self.name
+
+    @property
+    def details(self):
+        """
+        Generate a detailed string representation, e.g., for usage in scheduling
+        :return: string representation of that AK with all details
+        :rtype: str
+        """
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+        availabilities = ', \n'.join(f'{a.simplified}' for a in Availability.objects.select_related('event')
+                                     .filter(ak=self))
+        detail_string = f"""{self.name}{" (R)" if self.reso else ""}:
+
+        {self.owners_list}
+
+        {_('Interest')}: {self.interest}"""
+        if self.requirements.count() > 0:
+            detail_string += f"\n{_('Requirements')}: {', '.join(str(r) for r in self.requirements.all())}"
+        if self.types.count() > 0:
+            detail_string += f"\n{_('Types')}: {', '.join(str(r) for r in self.types.all())}"
+
+        # Find conflicts
+        # (both directions, those specified for this AK and those were this AK was specified as conflict)
+        # Deduplicate and order list alphabetically
+        conflicts = set()
+        if self.conflicts.count() > 0:
+            for c in self.conflicts.all():
+                conflicts.add(str(c))
+        if self.conflict.count() > 0:
+            for c in self.conflict.all():
+                conflicts.add(str(c))
+        if len(conflicts) > 0:
+            conflicts = list(conflicts)
+            conflicts.sort()
+            detail_string += f"\n{_('Conflicts')}: {', '.join(conflicts)}"
+
+        if self.prerequisites.count() > 0:
+            detail_string += f"\n{_('Prerequisites')}: {', '.join(str(p) for p in self.prerequisites.all())}"
+        detail_string += f"\n{_('Availabilities')}: \n{availabilities}"
+        return detail_string
+
+    @property
+    def owners_list(self):
+        """
+        Get a list of stringified representations of all owners
+
+        :return: list of owners
+        :rtype: list[str]
+        """
+        return ", ".join(str(owner) for owner in self.owners.all())
+
+    @property
+    def durations_list(self):
+        """
+        Get a list of stringified representations of all durations of associated slots
+
+        :return: list of durations
+        :rtype: list[str]
+        """
+        return ", ".join(str(slot.duration_simplified) for slot in self.akslot_set.select_related('event').all())
+
+    @property
+    def wish(self):
+        """
+        Is the AK a wish?
+        :return: true if wish, false if not
+        :rtype: bool
+        """
+        return self.owners.count() == 0
+
+    def increment_interest(self):
+        """
+        Increment the interest counter for this AK by one
+        without tracking that change to prevent an unreadable and large history
+        """
+        self.interest_counter += 1
+        self.skip_history_when_saving = True  # pylint: disable=attribute-defined-outside-init
+        self.save()
+        del self.skip_history_when_saving
+
+    @property
+    def availabilities(self):
+        """
+        Get all availabilities associated to this AK
+        :return: availabilities
+        :rtype: QuerySet[Availability]
+        """
+        return "Availability".objects.filter(ak=self)
+
+    @property
+    def edit_url(self):
+        """
+        Get edit URL for this AK
+        Will link to frontend if AKSubmission is active, otherwise to the edit view for this object in admin interface
+
+        :return: URL
+        :rtype: str
+        """
+        if apps.is_installed("AKSubmission"):
+            return reverse_lazy('submit:ak_edit', kwargs={'event_slug': self.event.slug, 'pk': self.id})
+        return reverse_lazy('admin:AKModel_ak_change', kwargs={'object_id': self.id})
+
+    @property
+    def detail_url(self):
+        """
+        Get detail URL for this AK
+        Will link to frontend if AKSubmission is active, otherwise to the edit view for this object in admin interface
+
+        :return: URL
+        :rtype: str
+        """
+        if apps.is_installed("AKSubmission"):
+            return reverse_lazy('submit:ak_detail', kwargs={'event_slug': self.event.slug, 'pk': self.id})
+        return self.edit_url
+
+    def save(self, *args, force_insert=False, force_update=False, using=None, update_fields=None):
+        # Auto-Generate Link if not set yet
+        if self.link == "":
+            link = self.event.base_url + self.name.replace(" ", "_")
+            # Truncate links longer than 200 characters (default length of URL fields in django)
+            self.link = link[:200]
+            # Tell Django that we have updated the link field
+            if update_fields is not None:
+                update_fields = {"link"}.union(update_fields)
+        super().save(*args,
+                     force_insert=force_insert, force_update=force_update, using=using, update_fields=update_fields)
+
+
+class Room(models.Model):
+    """ A room describes where an AK can be held.
+    """
+    name = models.CharField(max_length=64, verbose_name=_('Name'), help_text=_('Name or number of the room'))
+    location = models.CharField(max_length=256, blank=True, verbose_name=_('Location'),
+                                help_text=_('Name or number of the location'))
+    capacity = models.IntegerField(verbose_name=_('Capacity'),
+                                   help_text=_('Maximum number of people (-1 for unlimited).'))
+    properties = models.ManyToManyField(to=AKRequirement, blank=True, verbose_name=_('Properties'),
+                                        help_text=_('AK requirements fulfilled by the room'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    class Meta:
+        verbose_name = _('Room')
+        verbose_name_plural = _('Rooms')
+        ordering = ['location', 'name']
+        unique_together = ['event', 'name', 'location']
+
+    @property
+    def title(self):
+        """
+        Get title of a room, which consists of location and name if location is set, otherwise only the name
+
+        :return: title
+        :rtype: str
+        """
+        if self.location:
+            return f"{self.location} {self.name}"
+        return self.name
+
+    def __str__(self):
+        return self.title
+
+    def as_json_dict(self) -> dict[str, Any]:
+        """Return a json representation of this room object.
+
+        :return: The json dict representation is constructed
+            following the input specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        :rtype: dict[str, Any]
+        """
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+
+        # check if room is available for the whole event
+        # -> no time constraint needs to be introduced
+        if Availability.is_event_covered(self.event, self.availabilities.all()):
+            time_constraints = []
+        else:
+            time_constraints = [f"availability-room-{self.pk}"]
+
+        data = {
+            "id": self.pk,
+            "info": {
+                "name": self.name,
+            },
+            "capacity": self.capacity,
+            "fulfilled_room_constraints": list(self.properties.values_list("name", flat=True)),
+            "time_constraints": time_constraints
+        }
+
+        data["fulfilled_room_constraints"].append(f"fixed-room-{self.pk}")
+
+        if not any(constr.startswith("proxy") for constr in data["fulfilled_room_constraints"]):
+            data["fulfilled_room_constraints"].append("no-proxy")
+
+        data["fulfilled_room_constraints"].sort()
+        return data
+
+
+class AKSlot(models.Model):
+    """ An AK Mapping matches an AK to a room during a certain time.
+    """
+    ak = models.ForeignKey(to=AK, on_delete=models.CASCADE, verbose_name=_('AK'), help_text=_('AK being mapped'))
+    room = models.ForeignKey(to=Room, blank=True, null=True, on_delete=models.SET_NULL, verbose_name=_('Room'),
+                             help_text=_('Room the AK will take place in'))
+    start = models.DateTimeField(verbose_name=_('Slot Begin'), help_text=_('Time and date the slot begins'),
+                                 blank=True, null=True)
+    duration = models.DecimalField(max_digits=4, decimal_places=2, default=2, verbose_name=_('Duration'),
+                                   help_text=_('Length in hours'))
+
+    fixed = models.BooleanField(default=False, verbose_name=_('Scheduling fixed'),
+                                help_text=_('Length and time of this AK should not be changed'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    updated = models.DateTimeField(auto_now=True, verbose_name=_("Last update"))
+
+    class Meta:
+        verbose_name = _('AK Slot')
+        verbose_name_plural = _('AK Slots')
+        ordering = ['start', 'room']
+
+    def __str__(self):
+        if self.room:
+            return f"{self.ak} @ {self.start_simplified} in {self.room}"
+        return f"{self.ak} @ {self.start_simplified}"
+
+    @property
+    def duration_simplified(self):
+        """
+        Display duration of slot in format hours:minutes, e.g. 1.5 -> "1:30"
+        """
+        hours, minutes = divmod(self.duration * 60, 60)
+        return f"{int(hours)}:{int(minutes):02}"
+
+    @property
+    def start_simplified(self):
+        """
+        Display start time of slot in format weekday + time, e.g. "Fri 14:00"
+        """
+        if self.start is None:
+            return _("Not scheduled yet")
+        return self.start.astimezone(self.event.timezone).strftime('%a %H:%M')
+
+    @property
+    def time_simplified(self):
+        """
+        Display start and end time of slot in format weekday + time, e.g. "Fri 14:00 - 15:30" or "Fri 22:00 - Sat 02:00"
+        """
+        if self.start is None:
+            return _("Not scheduled yet")
+
+        start = self.start.astimezone(self.event.timezone)
+        end = self.end.astimezone(self.event.timezone)
+
+        return (f"{start.strftime('%a %H:%M')} - "
+                f"{end.strftime('%H:%M') if start.day == end.day else end.strftime('%a %H:%M')}")
+
+    @property
+    def end(self):
+        """
+        Retrieve end time of the AK slot
+        """
+        return self.start + timedelta(hours=float(self.duration))
+
+    @property
+    def seconds_since_last_update(self):
+        """
+        Return minutes since last update
+        :return: minutes since last update
+        :rtype: float
+        """
+        return (timezone.now() - self.updated).total_seconds()
+
+    def overlaps(self, other: "AKSlot"):
+        """
+        Check whether two slots overlap
+
+        :param other: second slot to compare with
+        :return: true if they overlap, false if not:
+        :rtype: bool
+        """
+        return self.start < other.end <= self.end or self.start <= other.start < self.end
+
+    def save(self, *args, force_insert=False, force_update=False, using=None, update_fields=None):
+        # Make sure duration is not longer than the event
+        if update_fields is None or 'duration' in update_fields:
+            event_duration = self.event.end - self.event.start
+            event_duration_hours = event_duration.days * 24 + event_duration.seconds // 3600
+            self.duration = min(self.duration, event_duration_hours)
+        super().save(*args,
+                     force_insert=force_insert, force_update=force_update, using=using, update_fields=update_fields)
+
+    def as_json_dict(self) -> dict[str, Any]:
+        """Return a json representation of the AK object of this slot.
+
+        :return: The json dict representation is constructed
+            following the input specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        :rtype: dict[str, Any]
+        """
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+
+        # check if ak resp. owner is available for the whole event
+        # -> no time constraint needs to be introduced
+
+        if self.fixed and self.start is not None:
+            ak_time_constraints = [f"fixed-akslot-{self.id}"]
+        elif not Availability.is_event_covered(self.event, self.ak.availabilities.all()):
+            ak_time_constraints = [f"availability-ak-{self.ak.pk}"]
+        else:
+            ak_time_constraints = []
+
+        def _owner_time_constraints(owner: AKOwner):
+            owner_avails = owner.availabilities.all()
+            if not owner_avails or Availability.is_event_covered(self.event, owner_avails):
+                return []
+            return [f"availability-person-{owner.pk}"]
+
+        conflict_slots = AKSlot.objects.filter(ak__in=self.ak.conflicts.all())
+        dependency_slots = AKSlot.objects.filter(ak__in=self.ak.prerequisites.all())
+        other_ak_slots = AKSlot.objects.filter(ak=self.ak).exclude(pk=self.pk)
+
+        ceil_offet_eps = decimal.Decimal(1e-4)
+
+        data = {
+            "id": self.pk,
+            "duration": math.ceil(self.duration / self.event.export_slot - ceil_offet_eps),
+            "properties": {
+                "conflicts": list((conflict_slots | other_ak_slots).values_list("pk", flat=True).order_by()),
+                "dependencies": list(dependency_slots.values_list("pk", flat=True).order_by()),
+            },
+            "room_constraints": list(self.ak.requirements.values_list("name", flat=True).order_by()),
+            "time_constraints": ["resolution"] if self.ak.reso else [],
+            "info": {
+                "name": self.ak.name,
+                "head": ", ".join([str(owner) for owner in self.ak.owners.order_by().all()]),
+                "description": self.ak.description,
+                "reso": self.ak.reso,
+                "duration_in_hours": float(self.duration),
+                "django_ak_id": self.ak.pk,
+                "types": list(self.ak.types.values_list("name", flat=True).order_by()),
+                },
+            }
+
+        data["time_constraints"].extend(ak_time_constraints)
+        for owner in self.ak.owners.all():
+            data["time_constraints"].extend(_owner_time_constraints(owner))
+
+        if self.ak.category:
+            category_constraints = AKCategory.create_category_optimizer_constraints([self.ak.category])
+            data["time_constraints"].extend(category_constraints)
+
+        if self.fixed and self.room is not None:
+            data["room_constraints"].append(f"fixed-room-{self.room.pk}")
+
+        if not any(constr.startswith("proxy") for constr in data["room_constraints"]):
+            data["room_constraints"].append("no-proxy")
+
+        data["room_constraints"].sort()
+        data["time_constraints"].sort()
+
+        return data
+
+class AKOrgaMessage(models.Model):
+    """
+    Model representing confidential messages to the organizers/scheduling people, belonging to a certain AK
+    """
+    ak = models.ForeignKey(to=AK, on_delete=models.CASCADE, verbose_name=_('AK'),
+                           help_text=_('AK this message belongs to'))
+    text = models.TextField(verbose_name=_("Message text"),
+                            help_text=_("Message to the organizers. This is not publicly visible."))
+    timestamp = models.DateTimeField(auto_now_add=True)
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+    resolved = models.BooleanField(verbose_name=_('Resolved'), default=False,
+                                   help_text=_('This message has been resolved (no further action needed)'))
+
+    class Meta:
+        verbose_name = _('AK Orga Message')
+        verbose_name_plural = _('AK Orga Messages')
+        ordering = ['-timestamp']
+
+    def __str__(self):
+        return f'AK Orga Message for "{self.ak}" @ {self.timestamp}'
+
+
+class ConstraintViolation(models.Model):
+    """
+    Model to represent any kind of constraint violation
+
+    Can have two different severities: violation and warning
+    The list of possible types is defined in :class:`ViolationType`
+    Depending on the type, different fields (references to other models) will be filled. Each violation should always
+    be related to an event and at least on other instance of a causing entity
+    """
+
+    class Meta:
+        verbose_name = _('Constraint Violation')
+        verbose_name_plural = _('Constraint Violations')
+        ordering = ['-timestamp']
+
+    class ViolationType(models.TextChoices):
+        """
+        Possible types of violations with their text representation
+        """
+        OWNER_TWO_SLOTS = 'ots', _('Owner has two parallel slots')
+        SLOT_OUTSIDE_AVAIL = 'soa', _('AK Slot was scheduled outside the AK\'s availabilities')
+        ROOM_TWO_SLOTS = 'rts', _('Room has two AK slots scheduled at the same time')
+        REQUIRE_NOT_GIVEN = 'rng', _('Room does not satisfy the requirement of the scheduled AK')
+        AK_CONFLICT_COLLISION = 'acc', _('AK Slot is scheduled at the same time as an AK listed as a conflict')
+        AK_BEFORE_PREREQUISITE = 'abp', _('AK Slot is scheduled before an AK listed as a prerequisite')
+        AK_AFTER_RESODEADLINE = 'aar', _(
+                'AK Slot for AK with intention to submit a resolution is scheduled after resolution deadline')
+        AK_CATEGORY_MISMATCH = 'acm', _('AK Slot in a category is outside that categories availabilities')
+        AK_SLOT_COLLISION = 'asc', _('Two AK Slots for the same AK scheduled at the same time')
+        ROOM_CAPACITY_EXCEEDED = 'rce', _('Room does not have enough space for interest in scheduled AK Slot')
+        SLOT_OUTSIDE_EVENT = 'soe', _('AK Slot is scheduled outside the event\'s availabilities')
+
+    class ViolationLevel(models.IntegerChoices):
+        """
+        Possible severities/levels of a CV
+        """
+        WARNING = 1, _('Warning')
+        VIOLATION = 10, _('Violation')
+
+    type = models.CharField(verbose_name=_('Type'), max_length=3, choices=ViolationType.choices,
+                            help_text=_('Type of violation, i.e. what kind of constraint was violated'))
+    level = models.PositiveSmallIntegerField(verbose_name=_('Level'), choices=ViolationLevel.choices,
+                                             help_text=_('Severity level of the violation'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    # Possible "causes":
+    aks = models.ManyToManyField(to=AK, blank=True, verbose_name=_('AKs'),
+                                 help_text=_('AK(s) belonging to this constraint'))
+    ak_slots = models.ManyToManyField(to=AKSlot, blank=True, verbose_name=_('AK Slots'),
+                                      help_text=_('AK Slot(s) belonging to this constraint'))
+    ak_owner = models.ForeignKey(to=AKOwner, on_delete=models.CASCADE, blank=True, null=True,
+                                 verbose_name=_('AK Owner'), help_text=_('AK Owner belonging to this constraint'))
+    room = models.ForeignKey(to=Room, on_delete=models.CASCADE, blank=True, null=True, verbose_name=_('Room'),
+                             help_text=_('Room belonging to this constraint'))
+    requirement = models.ForeignKey(to=AKRequirement, on_delete=models.CASCADE, blank=True, null=True,
+                                    verbose_name=_('AK Requirement'),
+                                    help_text=_('AK Requirement belonging to this constraint'))
+    category = models.ForeignKey(to=AKCategory, on_delete=models.CASCADE, blank=True, null=True,
+                                 verbose_name=_('AK Category'), help_text=_('AK Category belonging to this constraint'))
+
+    comment = models.TextField(verbose_name=_('Comment'), help_text=_('Comment or further details for this violation'),
+                               blank=True)
+
+    timestamp = models.DateTimeField(auto_now_add=True, verbose_name=_('Timestamp'), help_text=_('Time of creation'))
+    manually_resolved = models.BooleanField(verbose_name=_('Manually Resolved'), default=False,
+                                            help_text=_('Mark this violation manually as resolved'))
+
+    fields = ['ak_owner', 'room', 'requirement', 'category', 'comment']
+    fields_mm = ['_aks', '_ak_slots']
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.aks_tmp = set()
+        self.ak_slots_tmp = set()
+
+    def get_details(self):
+        """
+        Get details of this constraint (all fields connected to it)
+        :return: string of details
+        :rtype: str
+        """
+        # Stringify aks and ak slots fields (m2m)
+        output = [f"{_('AKs')}: {self._aks_str}",
+                  f"{_('AK Slots')}: {self._ak_slots_str}"]
+
+        # Stringify all other fields
+        for field in self.fields:
+            a = getattr(self, field, None)
+            if a is not None and str(a) != '':
+                output.append(f"{field}: {a}")
+        return ", ".join(output)
+
+    get_details.short_description = _('Details')
+
+    @property
+    def details(self):
+        """
+        Property: Details
+        """
+        return self.get_details()
+
+    @property
+    def edit_url(self) -> str:
+        """
+        Property: Edit URL for this CV
+        """
+        return reverse_lazy('admin:AKModel_constraintviolation_change', kwargs={'object_id': self.pk})
+
+    @property
+    def level_display(self) -> str:
+        """
+        Property: Severity as string
+        """
+        return self.get_level_display()
+
+    @property
+    def type_display(self) -> str:
+        """
+        Property: Type as string
+        """
+        return self.get_type_display()
+
+    @property
+    def timestamp_display(self) -> str:
+        """
+        Property: Creation timestamp as string
+        """
+        return self.timestamp.astimezone(self.event.timezone).strftime('%d.%m.%y %H:%M')
+
+    @property
+    def _aks(self):
+        """
+        Get all AKs belonging to this constraint violation
+
+        The distinction between real and tmp relationships is needed since many to many
+        relations only work for objects already persisted in the database
+
+        :return: set of all AKs belonging to this constraint violation
+        :rtype: set(AK)
+        """
+        if self.pk and self.pk > 0:
+            return set(self.aks.all())
+        return self.aks_tmp
+
+    @property
+    def _aks_str(self) -> str:
+        """
+        Property: AKs as string
+        """
+        if self.pk and self.pk > 0:
+            return ', '.join(str(a) for a in self.aks.all())
+        return ', '.join(str(a) for a in self.aks_tmp)
+
+    @property
+    def _ak_slots(self):
+        """
+        Get all AK Slots belonging to this constraint violation
+
+        The distinction between real and tmp relationships is needed since many to many
+        relations only work for objects already persisted in the database
+
+        :return: set of all AK Slots belonging to this constraint violation
+        :rtype: set(AKSlot)
+        """
+        if self.pk and self.pk > 0:
+            return set(self.ak_slots.all())
+        return self.ak_slots_tmp
+
+    @property
+    def _ak_slots_str(self) -> str:
+        """
+        Property: Slots as string
+        """
+        if self.pk and self.pk > 0:
+            return ', '.join(str(a) for a in self.ak_slots.select_related('event').all())
+        return ', '.join(str(a) for a in self.ak_slots_tmp)
+
+    def save(self, *args, **kwargs):
+        super().save(*args, **kwargs)
+        # Store temporary m2m-relations in db
+        for ak in self.aks_tmp:
+            self.aks.add(ak)
+        for ak_slot in self.ak_slots_tmp:
+            self.ak_slots.add(ak_slot)
+
+    def __str__(self):
+        return f"{self.get_level_display()}: {self.get_type_display()} [{self.get_details()}]"
+
+    def matches(self, other):
+        """
+        Check whether one constraint violation instance matches another,
+        this means has the same type, room, requirement, owner, category
+        as well as the same lists of aks and ak slots.
+        PK, timestamp, comments and manual resolving are ignored.
+
+        :param other: second instance to compare to
+        :type other: ConstraintViolation
+        :return: true if both instances are similar in the way described, false if not
+        :rtype: bool
+        """
+        if not isinstance(other, ConstraintViolation):
+            return False
+        # Check type
+        if self.type != other.type:
+            return False
+        # Make sure both have the same aks and ak slots
+        for field_mm in self.fields_mm:
+            s: set = getattr(self, field_mm)
+            o: set = getattr(other, field_mm)
+            if len(s) != len(o):
+                return False
+            if len(s.intersection(o)) != len(s):
+                return False
+        # Check other "defining" fields
+        for field in self.fields:
+            if getattr(self, field) != getattr(other, field):
+                return False
+        return True
+
+
+class DefaultSlot(models.Model):
+    """
+    Model representing a default slot,
+    i.e., a prefered slot to use for typical AKs in the schedule to guarantee enough breaks etc.
+    """
+
+    class Meta:
+        verbose_name = _('Default Slot')
+        verbose_name_plural = _('Default Slots')
+        ordering = ['-start']
+
+    start = models.DateTimeField(verbose_name=_('Slot Begin'), help_text=_('Time and date the slot begins'))
+    end = models.DateTimeField(verbose_name=_('Slot End'), help_text=_('Time and date the slot ends'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    primary_categories = models.ManyToManyField(to=AKCategory, verbose_name=_('Primary categories'), blank=True,
+                                                help_text=_(
+                                                        'Categories that should be assigned to this slot primarily'))
+
+    @property
+    def start_simplified(self) -> str:
+        """
+        Property: Simplified version of the start timetstamp (weekday, hour, minute) as string
+        """
+        return self.start.astimezone(self.event.timezone).strftime('%a %H:%M')
+
+    @property
+    def start_iso(self) -> str:
+        """
+        Property: Start timestamp as ISO timestamp for usage in calendar views
+        """
+        return timezone.localtime(self.start, self.event.timezone).strftime("%Y-%m-%dT%H:%M:%S")
+
+    @property
+    def end_simplified(self) -> str:
+        """
+        Property: Simplified version of the end timetstamp (weekday, hour, minute) as string
+        """
+        return self.end.astimezone(self.event.timezone).strftime('%a %H:%M')
+
+    @property
+    def end_iso(self) -> str:
+        """
+        Property: End timestamp as ISO timestamp for usage in calendar views
+        """
+        return timezone.localtime(self.end, self.event.timezone).strftime("%Y-%m-%dT%H:%M:%S")
+
+    def __str__(self):
+        return f"{self.event}: {self.start_simplified} - {self.end_simplified}"
+
+
+class EventParticipant(models.Model):
+    """ A participant describes a person taking part in an event."""
+
+    class Meta:
+        verbose_name = _('Participant')
+        verbose_name_plural = _('Participants')
+        ordering = ['name']
+
+    name = models.CharField(max_length=64, blank=True, verbose_name=_('Nickname'),
+                            help_text=_('Name to identify a participant by (in case of questions from the organizers)'))
+    institution = models.CharField(max_length=128, blank=True, verbose_name=_('Institution'), help_text=_('Uni etc.'))
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    requirements = models.ManyToManyField(to=AKRequirement, blank=True, verbose_name=_('Requirements'),
+                                          help_text=_("Participant's Requirements"))
+
+    def __str__(self) -> str:
+        string = _("Anonymous {pk}").format(pk=self.pk) if not self.name else self.name
+        if self.institution:
+            string += f" ({self.institution})"
+        return string
+
+    @property
+    def availabilities(self):
+        """
+        Get all availabilities associated to this EventParticipant
+        :return: availabilities
+        :rtype: QuerySet[Availability]
+        """
+        return "Availability".objects.filter(participant=self)
+
+    def as_json_dict(self) -> dict[str, Any]:
+        """Return a json representation of this participant object.
+
+        :return: The json dict representation is constructed
+            following the input specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        :rtype: dict[str, Any]
+        """
+        # local import to prevent cyclic import
+        # pylint: disable=import-outside-toplevel
+        from AKModel.availability.models import Availability
+
+        data = {
+            "id": self.pk,
+            "info": {"name": str(self)},
+            "room_constraints": list(self.requirements.values_list("name", flat=True).order_by()),
+            "time_constraints": [],
+        }
+        data["preferences"] = [
+            pref.as_json_dict()
+            for pref in AKPreference.objects.filter(
+                participant=self, preference__gt=0
+            ).select_related("slot").order_by()
+        ]
+
+        avails = self.availabilities.all()
+        if avails and not Availability.is_event_covered(self.event, avails):
+            # participant has restricted availability
+            if AKPreference.objects.filter(
+                event=self.event,
+                participant=self,
+                preference=AKPreference.PreferenceLevel.REQUIRED,
+            ):
+                # partipant is actually required for AKs
+                data["time_constraints"].append(f"availability-participant-{self.pk}")
+
+        data["time_constraints"].sort()
+        return data
+
+
+class AKPreference(models.Model):
+    """Model representing the preference of a participant to an AK."""
+
+    class Meta:
+        verbose_name = _('AK Preference')
+        verbose_name_plural = _('AK Preferences')
+        unique_together = [['event', 'participant', 'slot']]
+
+    event = models.ForeignKey(to=Event, on_delete=models.CASCADE, verbose_name=_('Event'),
+                              help_text=_('Associated event'))
+
+    participant = models.ForeignKey(to=EventParticipant, on_delete=models.CASCADE, verbose_name=_('Participant'),
+                              help_text=_('Participant this preference belongs to'))
+
+    slot = models.ForeignKey(to=AKSlot, on_delete=models.CASCADE, verbose_name=_('AK Slot'),
+                           help_text=_('AK Slot this preference belongs to'))
+
+    class PreferenceLevel(models.IntegerChoices):
+        """
+        Possible preference values
+        """
+        IGNORE = 0, _('Ignore')
+        PREFER = 1, _('Prefer')
+        STRONG_PREFER = 2, _("Strong prefer")
+        REQUIRED = 3, _("Required")
+
+    preference = models.PositiveSmallIntegerField(verbose_name=_('Preference'), choices=PreferenceLevel.choices,
+                                             help_text=_('Preference level for the AK'),
+                                             blank=False,
+                                             default=PreferenceLevel.IGNORE)
+
+    def __str__(self) -> str:
+        return "AKPreference: " + json.dumps(self.as_json_dict())
+
+    def as_json_dict(self) -> dict[str, int | bool]:
+        """Return a json representation of this AKPreference object.
+
+        :return: The json dict representation is constructed
+            following the input specification of the KoMa conference optimizer, cf.
+            https://github.com/Die-KoMa/ak-plan-optimierung/wiki/Input-&-output-format
+        :rtype: dict[str, Any]
+        """
+        preference_score = self.preference if self.preference != self.PreferenceLevel.REQUIRED else -1
+        return {
+            "ak_id": self.slot.pk,
+            "required": self.preference == self.PreferenceLevel.REQUIRED,
+            "preference_score": preference_score
+        }

AKModel/serializers.py

+from rest_framework import serializers
+
+from AKModel.models import AK, Room, AKSlot, AKTrack, AKCategory, AKOwner
+
+
+class AKOwnerSerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for AKOwner
+    """
+    class Meta:
+        model = AKOwner
+        fields = '__all__'
+
+
+class AKCategorySerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for AKCategory
+    """
+    class Meta:
+        model = AKCategory
+        fields = '__all__'
+
+
+class AKTrackSerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for AKTrack
+    """
+    class Meta:
+        model = AKTrack
+        fields = '__all__'
+
+
+class AKSerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for AK
+    """
+    class Meta:
+        model = AK
+        fields = '__all__'
+
+
+class RoomSerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for Room
+    """
+    class Meta:
+        model = Room
+        fields = '__all__'
+
+
+class AKSlotSerializer(serializers.ModelSerializer):
+    """
+    REST Framework Serializer for AKSlot
+    """
+    class Meta:
+        model = AKSlot
+        fields = '__all__'
+
+    treat_as_local = serializers.BooleanField(required=False, default=False, write_only=True)
+
+    def create(self, validated_data:dict):
+        # Handle timezone adaption based upon the control field "treat_as_local":
+        # If it is set, ignore timezone submitted from the browser (will always be UTC)
+        # and treat it as input in the events timezone instead
+        if validated_data['treat_as_local']:
+            validated_data['start'] = validated_data['start'].replace(tzinfo=None).astimezone(
+                validated_data['event'].timezone)
+        del validated_data['treat_as_local']
+        return super().create(validated_data)

AKModel/site.py

+from django.contrib.admin import AdminSite
+from django.utils.translation import gettext_lazy as _
+# from django.urls import path
+
+from AKModel.models import Event
+
+
+class AKAdminSite(AdminSite):
+    """
+    Custom admin interface definition (extend the admin functionality of Django)
+    """
+    index_template = "admin/ak_index.html"
+    site_header = f"AKPlanning - {_('Administration')}"
+    index_title = _('Administration')
+
+    def get_urls(self):
+        """
+        Get URLs -- add further views that are not related to a certain model here if needed
+        """
+        urls = super().get_urls()
+        urls += [
+            # path('...', self.admin_view(...)),
+        ]
+        return urls
+
+    def index(self, request, extra_context=None):
+        # Override index page rendering to provide extra context (the list of active events)
+        # to be used in the adapted template
+        if extra_context is None:
+            extra_context = {}
+        extra_context["active_events"] = Event.objects.filter(active=True)
+        return super().index(request, extra_context)

AKModel/templates/AKModel/load_fullcalendar.html

+{% load compress %}
+{% load static %}
+{% load i18n %}
+{% get_current_language as LANGUAGE_CODE %}
+
+{% compress js %}
+    <script src='{% static 'common/vendor/fullcalendar-scheduler/fullcalendar-6.0.2.js' %}'></script>
+    <script src='{% static 'common/vendor/fullcalendar-scheduler/fullcalendar.bootstrap5-5.0.2.min.js' %}'></script>
+
+    {% with 'common/vendor/fullcalendar-scheduler/locales/'|add:LANGUAGE_CODE|add:'.js' as locale_file %}
+        {% if LANGUAGE_CODE != "en" %}
+            {# Locale 'en' is included in main.js and does not exist separately #}
+            <script src="{% static locale_file %}"></script>
+        {% endif %}
+    {% endwith %}
+{% endcompress %}
+
+

AKModel/templates/AKModel/load_fullcalendar_availabilities.html

+{% load compress %}
+{% load static %}
+{% load i18n %}
+{% get_current_language as LANGUAGE_CODE %}
+
+{% compress js %}
+    <script src='{% static 'common/vendor/fullcalendar-scheduler/fullcalendar-6.0.2.js' %}'></script>
+    <script src='{% static 'common/vendor/fullcalendar-scheduler/fullcalendar.bootstrap5-5.0.2.min.js' %}'></script>
+    <script src="{% static "common/vendor/moment/moment-with-locales.js" %}"></script>
+    <script src="{% static "common/js/availabilities.js" %}"></script>
+
+    {% with 'common/vendor/fullcalendar-scheduler/locales/'|add:LANGUAGE_CODE|add:'.js' as locale_file %}
+        {% if LANGUAGE_CODE != "en" %}
+            {# Locale 'en' is included in main.js and does not exist separately #}
+            <script src="{% static locale_file %}"></script>
+        {% endif %}
+    {% endwith %}
+{% endcompress %}

AKModel/templates/AKModel/user.html

+{% extends 'base.html' %}
+
+{% load fontawesome_6 %}
+{% load i18n %}
+{% load static %}
+
+{% load tags_AKModel %}
+
+{% block breadcrumbs %}
+    <li class="breadcrumb-item">
+        {% if 'AKDashboard'|check_app_installed %}
+            <a href="{% url 'dashboard:dashboard' %}">AKPlanning</a>
+        {% else %}
+            AKPlanning
+        {% endif %}
+    </li>
+    <li class="breadcrumb-item">User: {{ user.get_username }}</li>
+{% endblock %}
+
+{% block content %}
+    {% include "messages.html" %}
+
+    <h1>{% trans "Hello" %} {{ user }}!</h1>
+
+    {% if user.is_staff %}
+        <a class="btn btn-primary" href="{% url "admin:index" %}">{% trans "Go to backend" %}</a>
+    {% else %}
+        <div class="alert alert-warning" style="margin-top:20px;margin-bottom: 20px;">
+            {% trans "Please wait for an administrator to confirm your account" %}
+        </div>
+    {% endif %}
+    <a class="btn btn-danger" href="{% url "logout" %}">{% trans "Logout" %}</a>
+
+{% endblock %}

AKModel/templates/admin/AKModel/action_intermediate.html

+{% extends "admin/base_site.html" %}
+{% load tags_AKModel %}
+
+{% load i18n %}
+{% load django_bootstrap5 %}
+{% load fontawesome_6 %}
+
+
+{% block title %}{{event}}: {{ title }}{% endblock %}
+
+{% block content %}
+    {% block action_preview %}
+        <p>
+            {{ preview|linebreaksbr }}
+        </p>
+    {% endblock %}
+
+    <form method="post">{% csrf_token %}
+        {% bootstrap_form form %}
+
+        <div class="float-end">
+            <button type="submit" class="save btn btn-success" value="Submit">
+                {% fa6_icon "check" 'fas' %} {% trans "Confirm" %}
+            </button>
+        </div>
+        <a href="javascript:history.back()" class="btn btn-info">
+            {% fa6_icon "times" 'fas' %} {% trans "Cancel" %}
+        </a>
+    </form>
+{% endblock %}

AKModel/templates/admin/AKModel/ak_csv_export.html

+{% extends "admin/base_site.html" %}
+
+{% load tz %}
+
+{% block content %}
+<pre>
+title;duration;who;requirements;prerequisites;conflicts;availabilities;category;types;track;reso;notes;
+{% for slot in slots %}{{ slot.ak.short_name }};{{ slot.duration }};{{ slot.ak.owners.all|join:", " }};{{ slot.ak.requirements.all|join:", " }};{{ slot.ak.prerequisites.all|join:", " }};{{ slot.ak.conflicts.all|join:", " }};{% for a in slot.ak.availabilities.all %}{{ a.start | timezone:event.timezone | date:"l H:i"  }} - {{ a.end | timezone:event.timezone | date:"l H:i" }}, {% endfor %};{{ slot.ak.category }};{{ slot.ak.types.all|join:", " }};{{ slot.ak.track }};{{ slot.ak.reso }};{{ slot.ak.notes }};
+{% endfor %}
+</pre>
+{% endblock %}

AKModel/templates/admin/AKModel/ak_json_export.html

+{% extends "admin/base_site.html" %}
+
+{% load tz %}
+
+{% block content %}
+
+<div class="mb-3">
+  <label for="export_single_line" class="form-label">Exported JSON:</label>
+  <input readonly type="text" name="export_single_line" class="form-control form-control-sm" value="{{ json_data_oneline }}"  style="font-family:var(--font-family-monospace);">
+</div>
+
+<div class="mb-3">
+  <label class="form-label">Exported JSON (indented for better readability):</label>
+  <pre class="prettyprint border rounded p-2">{{ json_data }}</pre>
+</div>
+
+<script>
+  $(document).ready(function() {
+    // JSON highlighting.
+    prettyPrint();
+    }
+  )
+</script>
+{% endblock %}

AKModel/templates/admin/AKModel/aks_by_user.html

+{% extends "admin/base_site.html" %}
+{% load tags_AKModel %}
+
+{% load i18n %}
+{% load tz %}
+{% load fontawesome_6 %}
+
+{% block title %}{% trans "AKs by Owner" %}: {{owner}}{% endblock %}
+
+{% block content %}
+    {% timezone event.timezone %}
+        <h2>[{{event}}] <a href="{% url 'admin:AKModel_akowner_change' owner.pk %}">{{owner}}</a> - {% trans "AKs" %}</h2>
+
+        <div class="row mt-4">
+            <table class="table table-striped">
+                {% for ak in owner.ak_set.all %}
+                    <tr>
+                        <td>{{ ak }}</td>
+                        {% if "AKSubmission"|check_app_installed %}
+                            <td class="text-end">
+                                <a href="{{ ak.detail_url }}" data-bs-toggle="tooltip"
+                                   title="{% trans 'Details' %}"
+                                   class="btn btn-primary">{% fa6_icon 'info' 'fas' %}</a>
+                                {% if event.active %}
+                                    <a href="{{ ak.edit_url }}" data-bs-toggle="tooltip"
+                                       title="{% trans 'Edit' %}"
+                                       class="btn btn-success">{% fa6_icon 'pencil-alt' 'fas' %}</a>
+                                {% endif %}
+                            {% endif %}
+                        </td>
+                    </tr>
+                {% empty %}
+                    <tr><td>{% trans "This user does not have any AKs currently" %}</td></tr>
+                {% endfor %}
+            </table>
+        </div>
+    {% endtimezone %}
+{% endblock %}

AKModel/templates/admin/AKModel/default_slot_editor.html

+{% extends "admin/AKModel/action_intermediate.html" %}
+{% load tags_AKModel %}
+{% load i18n admin_urls %}
+{% load static %}
+{% load django_bootstrap5 %}
+{% load tz %}
+
+{% block extrahead %}
+    {{ block.super }}
+    {% bootstrap_javascript %}
+    <script src="{% static 'common/vendor/jquery/jquery-3.6.3.min.js' %}"></script>
+    {% include "AKModel/load_fullcalendar_availabilities.html" %}
+
+    <script>
+        {% get_current_language as LANGUAGE_CODE %}
+
+        document.addEventListener('DOMContentLoaded', function () {
+            createAvailabilityEditors(
+                '{{ event.timezone }}',
+                '{{ LANGUAGE_CODE }}',
+                '{{ event.start | timezone:event.timezone | date:"Y-m-d H:i:s" }}',
+                '{{ event.end | timezone:event.timezone | date:"Y-m-d H:i:s" }}',
+                '00:15:00'
+            );
+        });
+    </script>
+{% endblock %}
+
+{% block action_preview %}
+    <h3>{{ event.name }}</h3>
+{% endblock %}
+

AKModel/templates/admin/AKModel/event_wizard/activate.html

+{% extends "admin/base_site.html" %}
+{% load tags_AKModel %}
+
+{% load i18n %}
+{% load django_bootstrap5 %}
+{% load fontawesome_6 %}
+{% load tz %}
+
+{% block title %}{% trans "New event wizard" %}: {{ wizard_step_text }}{% endblock %}
+
+{% block extrahead %}
+    {{ block.super }}
+    {{ form.media }}
+{% endblock %}
+
+{% block content %}
+    {% include "admin/AKModel/event_wizard/wizard_steps.html" %}
+
+    <div class="text-center btn-success disabled mt-3 mb-3" style="font-size: 8em;">
+        {% fa6_icon "copy" "fas" %}
+    </div>
+
+    <h5 class="mb-3">{% trans "Successfully imported.<br><br>Do you want to activate your event now?" %}</h5>
+
+    <form method="post">{% csrf_token %}
+        {% bootstrap_form form %}
+
+        <div class="float-end">
+            <button type="submit" class="save btn btn-success" value="Submit">
+            {% fa6_icon "check" 'fas' %} {% trans "Finish" %}
+        </button>
+        </div>
+
+        <a href="{% url 'admin:event_status' event.slug %}" class="btn btn-info">
+            {% fa6_icon "info" 'fas' %} {% trans "Status" %}
+        </a>
+    </form>
+
+{% endblock %}

AKModel/templates/admin/AKModel/event_wizard/created_prepare_import.html

+{% extends "admin/base_site.html" %}
+{% load tags_AKModel %}
+
+{% load i18n %}
+{% load django_bootstrap5 %}
+{% load fontawesome_6 %}
+{% load tz %}
+
+{% block title %}{% trans "New event wizard" %}: {{ wizard_step_text }}{% endblock %}
+
+{% block extrahead %}
+    {{ block.super }}
+    {{ form.media }}
+{% endblock %}
+
+{% block content %}
+    {% include "admin/AKModel/event_wizard/wizard_steps.html" %}
+
+    {% timezone event.timezone %}
+        <div class="card border-success mt-3 mb-3" style="max-width: 100%;">
+          <div class="card-header">{% trans "New event:" %}</div>
+          <div class="card-body">
+            <h4 class="card-title">{{event}}</h4>
+            <p class="card-text">{{ event.start }} - {{ event.end }}</p>
+          </div>
+        </div>
+    {% endtimezone %}
+
+    <div class="text-center btn-success disabled mb-3" style="font-size: 8em;">
+        {% fa6_icon "calendar-plus" "fas" %}
+    </div>
+
+
+
+    <h5 class="mb-3">{% trans "Your event was created and can now be further configured." %}</h5>
+
+    <form method="post">{% csrf_token %}
+        {% bootstrap_form form %}
+
+        <div class="float-end">
+            <a href="{% url 'admin:new_event_wizard_activate' event.slug %}" class="btn btn-info">
+                {% fa6_icon "forward" 'fas' %} {% trans "Skip Import" %}
+            </a>
+
+            <button type="submit" class="save btn btn-success" value="Submit">
+            {% fa6_icon "check" 'fas' %} {% trans "Continue" %}
+        </button>
+        </div>
+
+        <a href="{% url 'admin:event_status' event.slug %}" class="btn btn-info">
+            {% fa6_icon "info" 'fas' %} {% trans "Status" %}
+        </a>
+    </form>
+
+{% endblock %}