Object Services
| Title (Goal) | Support Fedora 3-style object classes (content models) - Object Services |
|---|---|
| Primary Actor | Repository architect & implementer |
| Scope | Data architecture and access |
| Level | High |
| Story (A paragraph or two describing what happens) |
|
Examples
- Given the myns:image node above, I want to run a method (sequencer?) that creates/updates a thumbnail datastream under it every time the master datastream is updated.
- The myns:image type constraints assures that master is always present so if a new myns:image is created, a master child is expected to run the method on.
- Some users should be able to attach a pre-defined mymix:published_web mixin to the same object; when that happens, a sequencer is there waiting to create aweb_thumbnail, a web_small and web_large datastreams as children of the object.
- Conversely, if the user removes mymix:published_web, the web_thumbnail,web_small and web_largedatastreams are destroyed.
Challenges
- How do we handle the creation process so that the object does not go through validation before all mandatory children are ingested?
Issues / limitations
- A mixin can define a mandatory type, but the mixin itself is not mandatory. If some editor removes the mixin, that would break the thumbnail method. In order to prevent that, access policies can be defined for who can remove or add a certain mixin; but for basic functionality not meant to be ever removed, a primary type would solve the problem more easily and elegantly.
- Stefano Cossu: tests should be made with transactions for Challenge #1 when https://www.pivotaltracker.com/s/projects/684825/stories/64058980 is fixed. If I am able to create a node with a primary type or mix-in that defines a mandatory child , and that child as well within a transaction, and the validation is performed ONLY after the transaction is committed, this would solve the issue.
