diff --git a/docs/dev/index.md b/docs/dev/index.md
index f935ca3..31013b3 100644
--- a/docs/dev/index.md
+++ b/docs/dev/index.md
@@ -1,3 +1,7 @@
 # Repapp - developer documentation
 
-![Test image](uml/test.png){ align=left }
\ No newline at end of file
+The Repapp is a repair assignment booking and management tool. 
+It tries to support all common workflows happening while organizing a repair café event.
+It's build using the Django web framework.
+
+
diff --git a/docs/dev/objects.md b/docs/dev/objects.md
new file mode 100644
index 0000000..8f80db3
--- /dev/null
+++ b/docs/dev/objects.md
@@ -0,0 +1,42 @@
+# Objects
+
+A *device* is an object owned by a *guest* which has some issue. To get support for fixing the issue, a *guest* provides the information about the *device* and requests a repair *appointment* during a *repair_cafe*.
+
+In case of ambiguities, a *organizer* or a *repairer* can raise a *consultation* request. This *consultation* request is sent to the *guest* to get the needed information. In addition, a *organizer* or a *repairer* can add an *comment* to a *device*.
+
+A *repair_cafe* happens at a specific date and location. It's an event which consists of *appointments* of *repairer* with *guests* to fix a *device*.
+
+To organize a *repair_cafe*, a *organizer* needs to know which *repairer* will attend a *repair_cafe*, to schedule repair *appointments*.
+
+![Objects](uml/objects_other.png)
+
+![Appointment](uml/objects_appointment.png)
+
+![Comment](uml/objects_comment.png)
+
+![Consultation](uml/objects_consultation.png)
+
+## Repair_Cafe
+
+A *repair_cafe* is a event happening at a specific date at a specific location. During a *repair_cafe* *appointments* of *guests* with *repairers* happens to fix broken *devices*.
+
+Field       | Type         | Description
+-------------------------------------------------------------
+location    | Char (200)   | location of the event
+address     | Char (200)   | address where the event happens
+event_date  | Date         | date when the event happens
+repairer    | many to many | will attend the event
+
+## Device
+
+## Appointment
+
+## Guest
+
+## Repairer
+
+## Organizer
+
+## Consultation
+
+## Comment
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diff --git a/docs/dev/stories.md b/docs/dev/stories.md
new file mode 100644
index 0000000..e69de29
diff --git a/docs/dev/uml/objects_appointment.png b/docs/dev/uml/objects_appointment.png
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diff --git a/docs/dev/uml/objects_appointment.puml b/docs/dev/uml/objects_appointment.puml
new file mode 100644
index 0000000..0db3859
--- /dev/null
+++ b/docs/dev/uml/objects_appointment.puml
@@ -0,0 +1,14 @@
+@startuml
+
+object Guest
+object Repairer
+object Organizer
+object Device
+object Appointment
+
+Appointment -- Organizer
+Appointment o-- Device
+Appointment o-- Repairer
+Appointment o-- Guest
+
+@enduml
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diff --git a/docs/dev/uml/objects_comment.png b/docs/dev/uml/objects_comment.png
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diff --git a/docs/dev/uml/objects_comment.puml b/docs/dev/uml/objects_comment.puml
new file mode 100644
index 0000000..42b7b7d
--- /dev/null
+++ b/docs/dev/uml/objects_comment.puml
@@ -0,0 +1,13 @@
+@startuml
+
+object Repairer
+object Organizer
+object Device
+object Comment
+
+Comment *-- Organizer
+Comment *-- Repairer
+Comment *-- Device
+Comment -- Comment
+
+@enduml
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diff --git a/docs/dev/uml/objects_consultation.png b/docs/dev/uml/objects_consultation.png
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diff --git a/docs/dev/uml/objects_consultation.puml b/docs/dev/uml/objects_consultation.puml
new file mode 100644
index 0000000..95b4b3d
--- /dev/null
+++ b/docs/dev/uml/objects_consultation.puml
@@ -0,0 +1,16 @@
+@startuml
+
+object Guest
+object Repairer
+object Organizer
+object Device
+object Comment
+object Consultation
+
+Consultation *-- Organizer
+Consultation *-- Repairer
+Consultation *-- Device
+Consultation *-- Guest
+Consultation -- Comment
+
+@enduml
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diff --git a/docs/dev/uml/objects_other.png b/docs/dev/uml/objects_other.png
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diff --git a/docs/dev/uml/objects_other.puml b/docs/dev/uml/objects_other.puml
new file mode 100644
index 0000000..2688d34
--- /dev/null
+++ b/docs/dev/uml/objects_other.puml
@@ -0,0 +1,19 @@
+@startuml
+
+object Guest
+object Organizer
+object Repairer
+object Device
+object Appointment
+object Repair_Cafe
+
+Repair_Cafe *-- "happens during" Appointment
+Repair_Cafe -- "organizes" Organizer
+Repair_Cafe -- "attends" Repairer
+Repair_Cafe -- "visits" Guest
+Repair_Cafe -- "is fixed" Device
+
+Guest -- Organizer
+Guest o-- Device
+
+@enduml
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diff --git a/docs/dev/uml/test.png b/docs/dev/uml/test.png
deleted file mode 100644
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diff --git a/docs/dev/uml/test.puml b/docs/dev/uml/test.puml
deleted file mode 100644
index 27ee0bf..0000000
--- a/docs/dev/uml/test.puml
+++ /dev/null
@@ -1,14 +0,0 @@
-@startuml
-
-start
-
-if (Graphviz installed?) then (yes)
-  :process all\ndiagrams;
-else (no)
-  :process only
-  __sequence__ and __activity__ diagrams;
-endif
-
-stop
-
-@enduml
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diff --git a/docs/dev/uml/users.png b/docs/dev/uml/users.png
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diff --git a/docs/dev/uml/users.puml b/docs/dev/uml/users.puml
new file mode 100644
index 0000000..7fc9a09
--- /dev/null
+++ b/docs/dev/uml/users.puml
@@ -0,0 +1,14 @@
+@startuml
+
+object User
+object Guest
+object Member
+object Organizer
+object Repairer
+
+User <|-- Guest
+User <|-- Member
+Member <|-- Organizer
+Member <|-- Repairer
+
+@enduml
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diff --git a/docs/dev/users.md b/docs/dev/users.md
new file mode 100644
index 0000000..e76cade
--- /dev/null
+++ b/docs/dev/users.md
@@ -0,0 +1,9 @@
+# Users
+
+Repapp distinguishes two user categories.
+
+A *guest* is a owner of an device. The *guest* is booking a repair appointment to get support from a repair café member to fix his device.
+
+A *member* can be an *organizer* or a *repairer*. A *organizer* is taking care of arranging the repair assignments, and needs to access the private contact data of a guest to do this job. A *repairer* is supporting the *guest* in fixing his device. The *repairer* only needs the details of the device in advance, but not the private contact data of the guest.
+
+![Users](uml/users.png)
\ No newline at end of file
diff --git a/mkdocs.yml b/mkdocs.yml
index 9a81e06..2a4f373 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -9,6 +9,9 @@ nav:
         - Daten-Modell: 'models.md'
     - 'Developer documentation':
         - Overview: 'dev/index.md'
+        - Users: 'dev/users.md'
+        - Objects: 'dev/objects.md'
+        - Stories: 'dev/stories.md'
     - 'Repair-Café & Makespace':
         - Repair-Café: https://www.repaircafe-hilpoltstein.de
         - Makespace: https://makes-hacks-hip.de