Expressing More Fedora Relationships Using RDF.

I think that Ben O'Stein makes an excellent point about the use of RDF to express the relations between individual Datastreams in his post "Internal object relationships - in the context of Fedora and Solr indexing.". His usage of dcterms:hasFormat seems certainly appropriate in this case.  I might take this a step further and suggest that much of the System level and descriptive "DC" metadata can be appropriately mapped into the RDF space for Fedora.

While ORE might be one possibility for expressing a complex digital object,  I caution that the perception around ORE is that one actually "needs it" to express relationships between resources when that is actually the very nature of RDF. The ability to assert relationships is a product of triple statements whose subject and object may contain references to resources and is wholly adequate enough to express the relationships in the manner that Ben has pointed out. I suggest this usage is actually more semantically meaningful than that of the generic concept of an Aggregation expressed in ORE.  In fact, I find that the specified use in RDF described by the ORE group is a two edged sword with the following difficult tradeoffs:

1. Using it instead of a more common relation can actually result in the loss of semantic richness in a graph of resources because it forces the relationships to be represented using ORE predicates rather than those more common and which carry richer meaning, this is very unlike dcterms:relation style predicates that are "free radicals" of semantic meaning that can be peppered throughout ones preexisting ontology.


2. If one wishes to retain that semantic richness, one has to duplicate the relations one already has alongside those of ORE, resulting in bloating of statements describing the same relationship with different predicates.

The only mechanism I can see to alleviate this with the ORE specification would be to actually extend/refine the ORE ontology in ones own RDFS/OWL ontology domain model, in the same way as ORE has done with Dublin Core. See thread...

http://groups.google.com/group/oai-ore/browse_thread/thread/e77d3ab643077dd3

Its only then that one can actually state in more explicit detail, the nature of the relationships in an aggregation. (I/E/ partOfCollection, hasFormat, isFormatOf without duplication.  Cheers to Ben for the excellent reuse of an existing common ontology rather than inventing a new one.