- From: Bijan Parsia <bparsia@isr.umd.edu>
- Date: Mon, 4 Apr 2005 16:16:47 -0400
- To: DAWG Mailing List <public-rdf-dawg@w3.org>
Working off: <http://www.w3.org/2000/06/webdata/xslt? xslfile=http%3A%2F%2Fwww.w3.org%2F2001%2Fsw%2FDataAccess%2Frq23%2Fdefns. xsl&xmlfile=http%3A%2F%2Fwww.w3.org%2F2001%2Fsw%2FDataAccess%2Frq23%2F&a uth=proxy&transform=Submit> --------------- """Definition: RDF Term An RDF Term is anything that can occur in the RDF data model.""" "RDF data model" is linked to section 3.1 (Graph Data Model) of the Concepts and Abstract Syntax document. That section is non-normative. The first line is also redundant, given the rest of the definition: """ let RDF-U be the set of all RDF URIs let RDF-L be the set of all RDF Literals let RDF-B be the set of all bNodes The set of RDF Terms, RDF-T, is RDF-U union RDF-L union RDF-B.""" So, I advise striking it or moving it to the explication text instead of the definition. (It's possible to read section 3.1 so that "triples" can occur in the RDF data model, yet it's clear that triple are not, themselves" RDF Terms.) --------------- """Definition: Query Variable Let V be the set of all query variables. V and RDF-T are disjoint.""" This doesn't look like a definition (i.e, there is no "such that"). It also not specified whether V is non-empty, and whether V is denumerable. Section 6.6 of C&AS makes these features clear for blank nodes: http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#section-blank- nodes Perhaps this definition could read similarly, e.g., "A query variable is a member of the set V where V is infinite and disjoint from RDF-T. V is otherwise arbitrary." The other possibility is to pick a non-arbitrary set with the desired features. E.g., V is the set of pair whose first element is the unicode string "?" and whose second element is an arbitrary unicode string. I believe such a V is disjoint from RDF-T, though you might make the type tag "<?>" to rule out bizarre uris of the future :) (BTW, is there a strong motivation for the RDF- prefix? It seems otiose and is hard to read, IMHO) --------------- It would be good to note in the comment on triple patterns with literal subjects that all Query Patterns will literal subjects will *fail* on any RDF document. I'm fine with them being legal in SPARQL, perhaps as a forward compatibility measure, but it's also nice to note their (current) futility. --------------- """Definition: Query Pattern A query has one main graph pattern. It is called the Query Pattern.""" There is no definition of Query. There is no definition of Graph Pattern. (Basic pattern and Graph Pattern -- Grouping, yes. See my earlier message). Can there be more than one main graph pattern? Are there non-main graph patterns? What's the difference? --------------- Ok, taking a break now. Foward looking a bit I see there's some sloppiness with the term "pattern". For example: "Definition: Constraints A pattern may be a constraint, which is a boolean-valued expression of variables and RDF Terms that restricts query solutions" "A pattern"? A triple pattern? A graph pattern? Are constraints part of Basic Patterns? (in which case, shouldn't they be part of the definition of basic pattern?) I'm afraid that order of exposition is getting in the way here. More later, I imagine. Cheers, Bijan.
Received on Monday, 4 April 2005 20:16:49 UTC