Iterations on repository API

[enikao]

The repository stores models as graphs.

We might include several aspects into the API:

• 25

• 28

• 27

• 26

• 23

• 30

• 29

  To reduce complexity, we'll tackle them in this order:

1. 25

2. 26

   Experience shows that retrofitting versioning creates a lot of work.

future: tbd

[enikao]

Let's use this issue to discuss prioritization.