- From: Richard Cyganiak <richard.cyganiak@hp.com>
- Date: Tue, 03 May 2005 20:58:19 +0100
- To: public-rdf-dawg-comments@w3.org
Comments on http://www.w3.org/2001/sw/DataAccess/rq23/ regarding the ORDER BY clause: >From the grammar: | [16] OrderExpression ::= FunctionCall | Var | [59] FunctionCall ::= URI '(' ArgList ')' This doesn't allow expressions like "?a + ?b" in the ORDER BY clause. Is this intentional? If not, this sentence from section 10.1 also needs updating: | An ordering condition can be a variable or a function call. >From section 10.1: | When ordering a solution sequence involves an expression, it | is possible that the ordering conditions do no give a | completely determined ordering for the sequence. In this case | the ordering of solutions that are not distinguished, is not | determined. What does the first part of the sentence refer to? AFAICT, ordering a solution sequence always involves an expression. There's also some redundancy with this later paragraph: | If the ordering criteria do not specify the order of values, | then the ordering in the solution sequence is undefined. | However, an implementation must consistently impose the same | order so that applying LIMIT/OFFSET will not miss any solutions. Also, s/ no / not / in the first paragraph. Section 10.1 defines an order for different types of RDF terms, starting with "no value assigned to the variable": | 1. (Lowest) no value assigned to the variable in this solution. I have two issues with this: There might be no "the variable", e.g. "ORDER BY my:func(?var1, ?var2)". And it should be more explicit if the sentence applies only to unbound variables, or also to solutions that generate type errors, e.g. "ORDER BY xsd:integer(?x)" where ?x is not bound to an appropriate literal.
Received on Thursday, 5 May 2005 01:57:51 UTC