- From: <Art.Barstow@nokia.com>
- Date: Thu, 1 Sep 2005 13:12:32 -0400
- To: <public-rdf-dawg-comments@w3.org>
- Cc: <Ora.Lassila@nokia.com>
Regarding the 2005-07-21 version of the SPARQL Query Language for RDF document, we have the following comments: 1) This document does not discuss in any way the *semantics* of the query language. We would like to see a more formal definition of queries (and their results) in terms of RDF semantics (right now, the query language seems to treat RDF graphs as merely data structures from which something can be extracted). Why would SPARQL now ignore RDF's model theory when one was created through a sizeable effort? 2) Given that RDF representations -- effectively -- are graphs, why would the W3C present a query language based on relational algebra? It is well known [1] that relational algebra is insufficient for querying graphs (generally, data structures that exhibit repetitive or recursive patterns). In order to query, say, hierarchies of arbitrary depth, the query language should have some means of expressing a transitive closure. 3) It does not seem possible to extend SPARQL to be used with OWL (primarily, perhaps, because of comment #1 above). Regards, Art Barstow --- [1] Aho, A.V., Ullman, J.D.: Universality of data retrieval languages. In: POPL ¹79: Proceedings of the 6th ACM SIGACT-SIGPLAN symposium on Principles of programming languages, ACM Press (1979) 110119.
Received on Thursday, 1 September 2005 17:12:43 UTC