Copying this to public-rdf-dawg comments for tracking purposes.
Follow-up discussion should happen there...
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Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541 0875 0F91 96DE 6E52 C29E
Forwarded message 1
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