1 files changed, 62 insertions, 0 deletions
diff --git a/DEVNOTES.md b/DEVNOTES.md
new file mode 100644
index 000000000..01f58fa0f
--- /dev/null
+++ b/DEVNOTES.md
@@ -0,0 +1,62 @@
+
+# Authorization Logic in Policies
+
+## Base Rules
+
+### ApplicationPolicy
+
+Policies inheriting from the `ApplicationPolicy` authorize _Undestructive_ _Permissions_ whiche are `index?` and
+`show?`. And forbid _Destructive_ _Permissions_ which are `create?`, `destroy?` & `update`.
+
+These _CRUD_ permissions are tied to to _Action_ permissions, `delete?`→ `destroy?`, `edit?` → `update? and `new?`→ `create?`.
+
+These three _Action_ permissions are not supposed to be overriden in `ApplicationPolicy` subclasses.
+
+
+### Common Policy Types
+
+There are two common policy types.
+
+#### Read Only Type Policy
+
+This corresponds to inheriting from  `ApplicationPolicy` without overriding one of the five aforementioned _CRUD_ permissions.
+
+The following Policies are of this type.
+
+  - `Company`
+  - `GroupOfLine`
+  - `Line` + custom
+  - `Network`
+  - `StopArea`
+
+#### Standard Type Policy
+
+The standard type policy inherits from `ApplicationPolicy` does not override any _Undesructive_ _Pemission_ but overrides the _Destructive_ ones.
+
+Normally, but not always they are overriden as follows
+
+```ruby
+      def <destructive>?
+        !archived? && organisation_match? && user.has_permission('<resource in plural form>.<action>')
+      end
+```
+
+There are some variations (**TO BE CLARIFIED**) concerning `organisation_match?`.
+
+The following Policies are of this type.
+
+  - `AccessLink`
+  - `AccessPoint`
+  - `Calendar` (*)
+  - `ConnectionLink`
+  - `JourneyPattern`
+  - `Referential` + custom
+  - `Route`
+  - `RoutingConstraintZone`
+  - `TimeTable` + custom
+
+`Calendar` is a strange exception where no user permission is checked for the _destructive_ _permissions_.
+
+
+
+