Structural Validation

Title (Goal)	Support Fedora 3-style object classes (content models) - Structural Validation
Primary Actor	Repository architect & implementer
Scope	Data architecture and access
Level	High
Story (A paragraph or two describing what happens)	As a repository manager, I can define "content models" that ensure the presence of defined datastreams A defined datastream has a defined name and a defined mime-type I can define which type(s), name(s) and number of children or properties a Fedora node can have

I have a myns:image asset type that is auto-assigned to assets ingested by Imaging department.
myns:image has mandatory properties and/or children such as a master datastream, of type nt:file or a subtype thereof.
myns:image assets can only have children of nt:file type. Ideally, that nt:file should be within a range of defined MIME types (not a critical feature for now)
I need a validation mechanism that throws an error if an user adds or updates a child or property that doesn't conform to that definition.

The default primary type, nt:folder, allows all Fedora nodes to have children of any type, with any name, in any number. There is no way to restrict that with Fedora's current tools.
The auto-assigned mixin type, fedora:resource, allows nodes to have properties of any type, with any name, in any number. Ditto as above.

Use case: AIC type hierarchy