Re: Short Essay: Squeezing RDF into a Java Object Model
W. E. Perry writes: > David Megginson wrote: > > > Obviously, there's a much more complex model underlying RDF than the > > spec lets on, and that model affects not only the ease or difficulty > > of implementing an object model, but also the difficult of many > > standard operations like queries against a collection of RDF > > statements and storage in a relational database. > May I respectfully submit that the problem is not the complexity of > the model underlying RDF, but its simplicity and relative freedom > from restriction, permitting the very sort of extension that leads > to the implementational problems David Megginson illustrates. I'm not certain that I follow -- I did not consider extensions at all in my essay. Certainly, it is possible to build complex layers on top of a simple data model, and much of what is in the RDF-syntax spec (such as the containers, rdf:type, rdf:value, rdf:Statement, etc.) together with all of the RDF-schema spec can be taken in that light; as a result, I considered none of that in my model. The problem is that the bottom-level, primitive model required for RDF support is itself rather complicated. It is certainly fair, in the model, to include Statement --------- - Subject - Predicate - Object but you also have to specify what a Subject, Predicate, and Object are. They are not simply resources/URIs, but have properties of their own: Subject ------- - value - isPrefix? Predicate --------- - value Object ------ - value - language - isResource? - isXML? This is the bare-bones RDF data model, according to my reading of the spec. Now, I will certainly admit that I have not been involved in the RDF design process, and may have misunderstood something: I encourage all members of XML Dev to feel free to correct me, no matter how experienced or inexperienced they may be with RDF. > Effectively it is just such a cumulative body of metadata which > David Megginson is seeking. It would provide the ability to refer > to components larger than simple subjects, predicates and objects, > such as resources as objects or prefixes as subjects. Such a > framework would comprehend and permit reference to any such objects > either top-down, from the perspectives of their larger containers, > or bottom-up from the perspective of their sub-components. I don't think that that's what I was looking for, though it certainly sounds interesting. Right now, I'm just considering the smallest possible data model required for implementing the RDF-syntax specification. All the best, David -- David Megginson david@m... http://www.megginson.com/ xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1 To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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