Content Models: Structural Definitions

Structural definitions depend on the approach a designer takes for the content model. In the simplest case, an object has just one content datastream. In such a case, no structural information is needed. This approach can be named 'simple model'.

Another option is to model one 'knowledge entity' which may have lots of constituent components as one single object in the repository ('compound model'). Each component is represented by a datastream. Each associated metadata record again becomes a datastream. A good example for this approach is the ARROW project (http://arrow.edu.au).

The last approach is an 'atomistic model' in which all of the constituent compounds of a knowledge entity become Fedora objects, tied together by an aggregation object which acts as an anchor for all constituent parts. Thus, each knowledge entity is represented by a network of objects or a graph. The National Science Digital Library (NSDL, http://www.nsdl.org) follows this design principle.

All three approaches have their pros and cons. Which approach to take strongly depends on the type of data you are working with and the type of services you want to implement on top of your repository.