In a recent post by Lee Feigenbaum, he talks about
Using RDF on the Web. Naturally I find this very interesting. In my work on
the Oort toolkit, I use an approach of "removing dimensions": namespaces, I18N (optionally), RDF-specific distinctions (collections vs. multiple properties) and other forms of graph traversing. This is done with declarative programming very similar to ORM-tools in dynamic languages (mainly class declarations with attributes describing desired data selection). The resulting objects become simple value trees — with the added bonus of automatic JSON-serialization.
Ideally, this approach will be deterministically reversible. I have not yet
implemented it, but the idea is that the declared classes (RdfQueries in Oort — let's call them "facets" here) could take JSON as input and reproduce triples. Using checksums of the JSON would make over-the-web editing possible.
Since the task of "updating" a subgraph is somewhat difficult at best, I think a basic "wipe and replace" approach may be simplest. There are many dangers here of course (removing a relation must not remove knowledge about its object — unless
perhaps if that object is a bnode..).
Albeit all of this is Python to the core now, nothing in the design — declarative as it is — prevents the approach from being more general. Indeed, such facets, were they themselves serializable, could be used as structured content retrieval over-the-web too. Ok, maybe I'm reinventing SPARQL now.. Or should I use SPARQL for their remote execution? It seems reasonable (I mean that's exactly how ORMs do SQL).
Now, I seem to end up in the RPC/RESTful camp with this. A solution to that could be: use the facets on the client, having them use SPARQL for retrieval. Then you have clients working against any kind of SPARQL endpoint, mashup-style. Still, if facets are completely reversible, they may be powerful, aware tools, and perhaps an alternative to SPARQL in intercommunication? That's a pipe dream for me right now though.
The SPARQL-way is of course
only for reading data. Fine, the RDF model may be too expressive (fine-grained) to be practical for
direct over-the-web editing in
specific situations anyway. A confined approach such as this JSON+checksums+"careful with nested knowledge" may be better for this.
I think of JSON-RPC here as I view e.g. microformats with GRDDL — it's leverage, not a final solution. RDF models are the ideal, we may just need reversible simplifications to gain mass usability. I touched upon
JSON for integrated apps, but stuff like Atom for "talking to strangers" in response to a previous post by Lee. His post which I refer to above hints at better stuff than just Atom if we want RDF all the way also in more specific apps.
So, what I'm saying is really: I also desire the best of two worlds. The RDF model is sound and extremely valuable, but after all, simple domain-specific object manipulation is what makes the web go round. A solution may be some form of O/R mapping for RDF. The difference is not wanting to
forget the data layer (there is no monster in the closet as there is with raw SQL..), just streamline some of the work with it.
Let's hope 2007 will be a good year for the knowledge revolution.
