- From: tessaris <tessaris@inf.unibz.it>
- Date: Thu, 26 Jan 2006 14:41:46 +0100
- To: Pat Hayes <phayes@ihmc.us>
- CC: RDF Data Access Working Group <public-rdf-dawg@w3.org>

Pat Hayes wrote: >> Moreover, I think that we should adopt a different notation for the >> variable substitution in graph templates, since it looks the same as >> the one for BGP but it behaves differently. In particular wrt >> variables not present in the domain of a pattern solution. > > > There once was a tweak in the definition of substitution mapping which I > think handles this, where S(v)=v if v is outside the domain of S, so S > maps V to (RDF_T union V). This makes all S's total on templates and > maps templates to templates (graphs being the special case of templates > with no variables). Would this handle the issue that you are referring > to? (If not, I'd like to see an example, because in that case Im not > following you.) It wont take care of the problem, since by the definition in 10.3.2: """ Definition: Graph Template A graph template is a set of triple patterns. If T = { t_j | j = 1,2 ... m } is a graph template and S is a solution then S(t_j) is a set of one RDF triple if all variables in t_j are in the domain of S. S(t_j) is the empty set otherwise. Write S(T) for the union of S(t_j). """ triples with variables without assignment "disappear"; while mapping the variables into themselves would generate an RDF graph with variables. --sergio

Received on Thursday, 26 January 2006 13:42:17 UTC