OpenDocument: Mixing Metadata
As the OpenDocument TC contemplates supporting RDF for document metadata, I am talking to them about upgrading the bibliographic support. I have been arguing that the two ought to be considered together, and that it makes sense to start to think about a comprehensive metadata approach in OD: one where the same framework is used to represent not just the document as a whole, but also embedded parts, such as figures, or images, or bibliographic references.
So how might this work?
OpenDocument is fundamentally an XML file format, so if it supports RDF, it’s important that it does so in a way that’s still amenable to XML processing. Yet the XML RDF syntax is so flexible that it makes XML processing rather difficult. So perhaps as a first principle, we ought to adopt an approach something like in DOAP and say that OD ought to support a constrained subset of RDF, where the syntax is clean XML, which is also happens to be RDF.
It turns out RELAX NG is nicely suited to handling the RDF model, with its ability to handle unordered content (the interleave feature), and so forth. So let’s say we define a clean RDF subset in RELAX NG. Let’s further say that we include support for Dublin Core in that base metadata schema.
Now, what about bibliographic metadata? A more traditional approach would define an entire standalone schema. This is the MODS approach. Yet that makes little sense in this context, so instead we include the base schema, override some of the structural definitions to allow citation-specific typing and add additional metadata properties. Otherwise, however, we use the same core metadata properties as are in the document metadata support. Because we are using the RDF model, adding new namespaced content is easy and predictable, and we now have a nice balance of flexibility backed up by the rigor of an underlying model.
The view from my xml editor:
[update: I've just posted the schemas here in case anyone is interested. They're just for demo, but include one that does generic constrained RDF validation, another for a core set of metadata, and the last a bib schema that customizes the second. The archive includes two example instances that are valid against the first and the third. In contrast to Adobe's XMP, I add what for me are essentials like support for xml literals (think, for example, embedded MathML in titles and abstracs) and at least basic support for rdf:type, while removing rdf:Alt and rdf:Bag, as well as the restriction that all resource must be wrapped in an rdf:Description element.]
[...] Bruce Darcus favours constrained/subsetted RDF/XML: OpenDocument: Mixing Metadata Danny@13:07 | Semantic Web [...]
[...] Earlier I discussed one way I envision expanding metadata support in OpenDocument. That consisted of using some RELAX NG-magic to constrain the structure of metadata representation, but allowing it to be easily extended. [...]