- From: David Allsopp <dallsopp@signal.dera.gov.uk>
- Date: Fri, 09 Feb 2001 09:35:12 +0000
- CC: www-rdf-interest@w3.org
"Matola,Tod" wrote: > > I agree as well. I have been leaning towards something like: > RDF Query Specification [1] > from Ashok Malhotra (IBM) <petsa@us.ibm.com> and Neel Sundaresan (IBM) > <neel@almaden.ibm.com> > > Just wonder how others felt about it. It doesn't seem realistic to write queries in that syntax (although you could use that specification of triples, created from a more concise syntax) - for example <rdfq:rdfquery> <rdfq:From eachResource="http://www.research.ibm.com/people/"> <rdfq:Select> <rdfq:Property name="??BelongTo" /> <rdfq:Select> <rdfq:Condition> <rdfq:greaterThan> <rdfq:Property name="Budget" /> <rdf:Integer>1000000</rdf:Integer> </rdfq:greaterThan> </rdfq:Condition> </rdfq:Select> </rdfq:Select> </rdfq:From> </rdfq:rdfquery> which might be expressed in an SQL-like syntax as something like: select ?x from http://www.research.ibm.com/people/ where (?x $$BelongTo ?y),(?x Budget >1000000) > Second what would the result of such a query (regardless of the QL) be? A > list of triples, a list of lists of triples, a RDF document or list of RDF > documents? From my perspective, working with software agents message-passing over a network, it's useful to be able to return complete RDF document(s), which an agent can merge into its own Model if required. However, if the agents are extracting information from their in-memory/on-disk database for their own use, they just need primitive values (String, int). I think both styles are needed. My own experimental query language implementation allows: select ?x ?y where (?x rdf:type abc:SomeType)(?x foo:bar ?y) select triples where (?x ... select reachable http://URI.of.some.resource/foo The first form just returns the requested values as an array of strings. The second form performs the same query, but returns the traversed triples, which can be collected in a Model, serialised and sent to another agent. The third form returns all the triples which are reachable from some resource; very useful for my particular application domain, as I don't want to have to send either multiple queries (given that we may be communicating by message-passing over an unreliable slow network) or excessively complex queries, to extract all the information about a particular resource Regards, David Allsopp -- The peason-molesworth space ship threatened by wild mercurian maths masters lies disabled in the onion bed of the kitchen garden. Meanwhile in the master's common room, Sigismund arbuthnot the mad maths master musters his rhomboids...
Received on Friday, 9 February 2001 04:40:29 UTC