- From: Jorge Pérez <jperez@utalca.cl>
- Date: Wed, 19 Apr 2006 10:54:29 -0400
- To: public-rdf-dawg-comments@w3.org
Hi! In the last draft, little attention is put on group graph patterns and "combinations" of group graph patterns. The draft says nothing about how the solution of WHERE { { A . } { B . } } is. There is just an example in where A and B are triple patterns, in which case the above WHERE clause is the same as WHERE { A . B . } but what if A or B are more complex graph patterns? It is not clear what the example is trying to say: 1) does it say that {} (inside other {}) are useless and on can just omit them? and then {{ A. } { B. }} is alway equal to { A. B. } 2) Other possiblity of evaluation is to think that { A. } and { B. } are graph patterns in the same group graph pattern, aplying the group graph pattern formal definition, a solution to the pattern { { A. } { B. } } must *independently* match the patterns A and B. what is the right? When looking in some implementations (SPARQLer and others) it seems that they are just omiting {}, i.e. using 1). following my example in http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2006Apr/0020.html what would be the answer for WHERE { { ?B :titlename ?N . } { ?B :year ?Y . OPTIONAL { ?B :authorname ?N } } } if one agree with 2) the solution must be the same as the solution for WHERE { { ?B :year ?Y . OPTIONAL { ?B :authorname ?N } } { ?B :titlename ?N . } } but implementations gave me differents results... Note that there may be more complex forms of combinations, so this issues deserves clarifications. If the editors agree with 1) then for simplicity the {} must be refused inside other {}, this is the most simple way to avoid the problem, for example { A. { B. { C. } { D. }} . OPTIONAL E. }} == { A. B. C. D. OPTIONAL E. } If they agree with 2) (not the most simple but seems to be the more "natural") I think that some clarifications may be added to the draft. - Jorge ------------------------------------------------- Este mensaje fue enviado por: http://webmail.utalca.cl
Received on Wednesday, 19 April 2006 14:58:49 UTC