Danny Ayers wrote:
Redland I believe associates every statement with a "context" so the context can provide any provenance info. These sort of things are fine internal within a system but aren't too helpful if you want to share that info and/or use it as part of the RDF (RDFS/OWL) inferencing.
4Suite also does something this. I'd speculate that most uses of RDF in production/commercial scenarios are using quads.
Long-term (i.e. it's unlikely to be in a W3C spec in the near future) there's Named Graphs as a very promising extension of RDF, for which the theory has been worked out and is nice & intuitive.
That's good to hear, because the provenance issues do tend to limit RDF usefulness.
A third approach to provenance is already supported by RDF,
reification. I still get very confused over this, Shelley Powers
called it "The Big Ugly". It's a bit like quotation but /different/ -
there is explanation in the Primer [2]. I've not used it myself, but a
presentation I saw last week convinced me the approach can work
Reification only works because it's a semantic free for all - there's no consensus as to what it means, so you can pretty much get it to mean anything you want to mean [it's like our link extension construct but worse]. The fact that we can say it's a bit like quotation while describing it being used for provenance is a something of a issue - never mind that reification does not appear do what it was designed to do, which is different again from quotation or provenance, or that none of those things are reification in the technical sense of the word. Ack. It's a lasting regret from my time on the RDF WG that we didn't get rid of it.
cheers Bill
