diff --git a/app/src/main/java/com/planify/mobile/domain/model/BackendType.kt b/app/src/main/java/com/planify/mobile/domain/model/BackendType.kt
new file mode 100644
index 0000000..a37643b
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/BackendType.kt
@@ -0,0 +1,3 @@
+package com.planify.mobile.domain.model
+
+enum class BackendType { LOCAL, CALDAV, TODOIST }
diff --git a/app/src/main/java/com/planify/mobile/domain/model/DueDate.kt b/app/src/main/java/com/planify/mobile/domain/model/DueDate.kt
new file mode 100644
index 0000000..72e7508
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/DueDate.kt
@@ -0,0 +1,16 @@
+package com.planify.mobile.domain.model
+
+data class DueDate(
+    val date: String,
+    val timezone: String? = null,
+    val isRecurring: Boolean = false,
+    val recurrencyType: RecurrencyType = RecurrencyType.NONE,
+    val recurrencyInterval: Int = 1,
+    val recurrencyWeekDays: List<Int> = emptyList(),
+    val recurrencyCount: Int? = null,
+    val recurrencyEnd: String? = null,
+)
+
+enum class RecurrencyType {
+    NONE, MINUTELY, HOURLY, EVERY_DAY, EVERY_WEEK, EVERY_MONTH, EVERY_YEAR
+}
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Label.kt b/app/src/main/java/com/planify/mobile/domain/model/Label.kt
new file mode 100644
index 0000000..ebfe368
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Label.kt
@@ -0,0 +1,12 @@
+package com.planify.mobile.domain.model
+
+data class Label(
+    val id: String,
+    val name: String,
+    val color: String,
+    val order: Int = 0,
+    val sourceId: String? = null,
+    val backendType: BackendType = BackendType.LOCAL,
+    val isFavorite: Boolean = false,
+    val isDeleted: Boolean = false,
+)
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Project.kt b/app/src/main/java/com/planify/mobile/domain/model/Project.kt
new file mode 100644
index 0000000..9bed99c
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Project.kt
@@ -0,0 +1,25 @@
+package com.planify.mobile.domain.model
+
+data class Project(
+    val id: String,
+    val name: String,
+    val color: String = "#4CAF50",
+    val emoji: String? = null,
+    val parentId: String? = null,
+    val sourceId: String? = null,
+    val backendType: BackendType = BackendType.LOCAL,
+    val isInbox: Boolean = false,
+    val isFavorite: Boolean = false,
+    val isArchived: Boolean = false,
+    val isDeleted: Boolean = false,
+    val viewStyle: ViewStyle = ViewStyle.LIST,
+    val sortedBy: SortBy = SortBy.MANUAL,
+    val sortAscending: Boolean = true,
+    val childOrder: Int = 0,
+    val calendarUrl: String? = null,
+    val syncId: String? = null,
+)
+
+enum class ViewStyle { LIST, BOARD }
+
+enum class SortBy { MANUAL, NAME, DUE_DATE, ADDED_DATE, PRIORITY }
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Reminder.kt b/app/src/main/java/com/planify/mobile/domain/model/Reminder.kt
new file mode 100644
index 0000000..8d415c7
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Reminder.kt
@@ -0,0 +1,11 @@
+package com.planify.mobile.domain.model
+
+data class Reminder(
+    val id: String,
+    val taskId: String,
+    val type: ReminderType,
+    val dueDate: DueDate? = null,
+    val minutesOffset: Int? = null,
+)
+
+enum class ReminderType { ABSOLUTE, RELATIVE }
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Section.kt b/app/src/main/java/com/planify/mobile/domain/model/Section.kt
new file mode 100644
index 0000000..c4215c3
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Section.kt
@@ -0,0 +1,13 @@
+package com.planify.mobile.domain.model
+
+data class Section(
+    val id: String,
+    val name: String,
+    val projectId: String,
+    val order: Int = 0,
+    val isArchived: Boolean = false,
+    val isDeleted: Boolean = false,
+    val collapsed: Boolean = false,
+    val icalUrl: String? = null,
+    val etag: String? = null,
+)
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Source.kt b/app/src/main/java/com/planify/mobile/domain/model/Source.kt
new file mode 100644
index 0000000..9b8487b
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Source.kt
@@ -0,0 +1,26 @@
+package com.planify.mobile.domain.model
+
+data class Source(
+    val id: String,
+    val type: SourceType,
+    val displayName: String,
+    val addedAt: String,
+    val updatedAt: String,
+    val isVisible: Boolean = true,
+    val lastSync: String? = null,
+    val caldavData: SourceCalDavData? = null,
+)
+
+enum class SourceType { LOCAL, CALDAV }
+
+data class SourceCalDavData(
+    val serverUrl: String,
+    val username: String,
+    val calendarHomeUrl: String? = null,
+    val userDisplayName: String? = null,
+    val userEmail: String? = null,
+    val caldavType: CalDavType = CalDavType.GENERIC,
+    val ignoreSsl: Boolean = false,
+)
+
+enum class CalDavType { NEXTCLOUD, GENERIC }
diff --git a/app/src/main/java/com/planify/mobile/domain/model/Task.kt b/app/src/main/java/com/planify/mobile/domain/model/Task.kt
new file mode 100644
index 0000000..0632479
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/model/Task.kt
@@ -0,0 +1,28 @@
+package com.planify.mobile.domain.model
+
+data class Task(
+    val id: String,
+    val content: String,
+    val description: String = "",
+    val projectId: String,
+    val sectionId: String? = null,
+    val parentId: String? = null,
+    val priority: Int = 4,
+    val checked: Boolean = false,
+    val dueDate: DueDate? = null,
+    val deadlineDate: String? = null,
+    val labels: List<String> = emptyList(),
+    val pinned: Boolean = false,
+    val collapsed: Boolean = false,
+    val childOrder: Int = 0,
+    val addedAt: String = "",
+    val updatedAt: String = "",
+    val completedAt: String? = null,
+    val itemType: ItemType = ItemType.TASK,
+    val calendarEventUid: String? = null,
+    val icalUrl: String? = null,
+    val etag: String? = null,
+    val responsibleUid: String? = null,
+)
+
+enum class ItemType { TASK, NOTE }
diff --git a/app/src/main/java/com/planify/mobile/domain/repository/ProjectRepository.kt b/app/src/main/java/com/planify/mobile/domain/repository/ProjectRepository.kt
new file mode 100644
index 0000000..152dc82
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/repository/ProjectRepository.kt
@@ -0,0 +1,15 @@
+package com.planify.mobile.domain.repository
+
+import com.planify.mobile.domain.model.Project
+import kotlinx.coroutines.flow.Flow
+
+interface ProjectRepository {
+    fun getAllProjects(): Flow<List<Project>>
+    fun getFavoriteProjects(): Flow<List<Project>>
+    fun getSubProjects(parentId: String): Flow<List<Project>>
+    suspend fun getProjectById(id: String): Project?
+    suspend fun getInboxProject(): Project?
+    suspend fun insertProject(project: Project)
+    suspend fun updateProject(project: Project)
+    suspend fun deleteProject(id: String)
+}
diff --git a/app/src/main/java/com/planify/mobile/domain/repository/TaskRepository.kt b/app/src/main/java/com/planify/mobile/domain/repository/TaskRepository.kt
new file mode 100644
index 0000000..90556dd
--- /dev/null
+++ b/app/src/main/java/com/planify/mobile/domain/repository/TaskRepository.kt
@@ -0,0 +1,18 @@
+package com.planify.mobile.domain.repository
+
+import com.planify.mobile.domain.model.Task
+import kotlinx.coroutines.flow.Flow
+
+interface TaskRepository {
+    fun getTasksByProject(projectId: String): Flow<List<Task>>
+    fun getTasksBySection(sectionId: String): Flow<List<Task>>
+    fun getInboxTasks(): Flow<List<Task>>
+    fun getTodayTasks(): Flow<List<Task>>
+    fun getOverdueTasks(): Flow<List<Task>>
+    fun getSubTasks(parentId: String): Flow<List<Task>>
+    suspend fun getTaskById(id: String): Task?
+    suspend fun insertTask(task: Task)
+    suspend fun updateTask(task: Task)
+    suspend fun deleteTask(id: String)
+    suspend fun checkTask(id: String, checked: Boolean)
+}