- From: Ian Horrocks <horrocks@cs.man.ac.uk>
- Date: Thu, 8 Sep 2005 14:14:40 +0100
- To: public-rdf-dawg@w3.org
Two comments/questions: Firstly, I strongly support the suggestion to define query answers in terms of entailment rather than subgraph. Using an entailment based definition has numerous advantages, and no disadvantages that I can see. Entailment based definition: - is widely used and very well understood - is concise, clear and unambiguous - builds on existing semantic definitions - can deal with a wide variety of languages, including RDF, RDFS, OWL, SWRL and FOL, simply by referring to the existing entailment semantics for the relevant language Subgraph based definition: - is not widely used, not well understood, and not *known* to work at all (at least not for more expressive languages) - is verbose, obfuscated (it seems capable of confusing even expert logicians), and may even be ambiguous - ignores existing semantic definitions - cannot easily deal with more expressive languages, and may even be incapable of doing so Can someone please explain to me why the subgraph based definition has been preferred? Secondly, IMHO, the minimum requirement for a query language standard is that, independently of the features and capabilities of any given implementation, it should define what would constitute a sound and complete answer for a given language, dataset and query. It is not at all clear that, in its current form, SPARQL satisfies this requirement. Am I missing something? Ian
Received on Thursday, 8 September 2005 13:16:47 UTC