Element Hierarchy Extension Point & Library

The UI in Rodin 2.x contains an extension point org.eventb.ui.editorItems that groups the both following information:

• the definition of elements and attributes and their hierarchy,
• the information needed to correctly display these elements in the various editors and UI components.

It appears obvious that the first information should be defined from an extension that belongs to the Database. To fullfil the above statement, the current extension point org.eventb.ui.editorItems should be split in two.

Proposal

• The part concerning element definition and hierarchy will go to a dedicated extension point in the database.
• The part concerning how to display elements and UI related info will stay in the editorItems extension point and shall point to an element definitions and hierachy.

The proposal should concern :

- Relationship declaration (new extension point)
- API to test these relations and traverse them
- Enforcement of the authorized relations when modifying the DB
- Behaviour while loading a file (including a file with invalid parent-child relations occurrences)
- What about the compatibilty with the file upgrade mechanism?