- From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
- Date: Mon, 12 Apr 2010 17:31:48 +0100
- To: Andy Seaborne <andy.seaborne@talis.com>
- Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
[snip] >> Propsed text: >> >> 4 -- Each SPARQL extension MUST provide conditions, which guarantee >> that the answer set for every BGP and AG is uniquely specified up to >> RDF graph equivalence. The conditions SHOULD prevent trivial infinite >> answers such as those from axiomatic triples and infinite answers that >> just differ in the identity of blank nodes. [snip] > The first is fine but "trivial" has both technical and non-technical senses. > Can we ask the entailment regime to define what "trivial" means for each > regime? > > Maybe: > """ > , and should provide further conditions to prevent trivial infinite answers > as appropriate to the regime. > """ That could be an alternative. What I understand as "trivial" and what the current regimes filter out are those answers that you can reconstruct from the returned answers without knowing the queried graph, so maybe I can try and make the more precise. E.g., for any of the entailment regimes you can "complete" the finite answer set into the "real" and possibly infinite answer set by adding all answers with rdf:_n from the axiomatic triples and by replacing each answer with a blank node with infinitely many copies that just differ in the blank node names. This is obviously not what anybody would want to do and it is also not too trivial because BGPs do not just consist of one triple and interdependencies have to be considered. Thus, if we go in this direction and make "trivial" that precise, then for each regime I guess I would have to prove that we actually can construct the real answer from any filtered one and I'd rather avoid that. Other than that this is probably what we really want to filter out, answers that can be reconstructed independently of the queried graph or rule set in case of RIF. Birte > Andy > > > -- Dr. Birte Glimm, Room 306 Computing Laboratory Parks Road Oxford OX1 3QD United Kingdom +44 (0)1865 283529
Received on Monday, 12 April 2010 16:32:25 UTC