W3C home > Mailing lists > Public > public-rdf-dawg-comments@w3.org > March 2006

Re: SPARQL: arguments for built-in calls to generic? [OK?]

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 13 Mar 2006 14:58:05 +0000
Message-ID: <4415887D.1020006@hp.com>
To: Arjohn Kampman <arjohn.kampman@aduna.biz>
CC: public-rdf-dawg-comments@w3.org



Arjohn Kampman wrote:
> Most of the built-in calls defined in the grammar in "[57] BuiltInCall"
> operate on arguments of type Expression, which includes boolean and
> mathematical operations. Most of these built-in calls, however, only
> produce results when operating on IRIs, literals and/or blank nodes.
> IMHO, it would be better to enforce this through the grammer, preventing
> people from writing expressions that are correct syntactically, but not
> semantically, like "lang( 3 + 4 )" and "isBlank(?var = foo:bar)".
> Changing this production rule to the following should prevent such
> expressions:
> 
> FunctionOrVar ::= IRIrefOrFunction | Var
> 
> BuiltInCall ::= 'STR' '(' FunctionOrVar ')'
>                | 'LANG' '(' FunctionOrVar ')'
>                | 'LANGMATCHES' '(' FunctionOrVar ',' String ')'
>                | 'DATATYPE' '(' FunctionOrVar ')'
>                | 'BOUND' '(' Var ')'
>                | 'isIRI' '(' FunctionOrVar ')'
>                | 'isURI' '(' FunctionOrVar ')'
>                | 'isBLANK' '(' FunctionOrVar ')'
>                | 'isLITERAL' '(' FunctionOrVar ')'
>                | RegexExpression
> 
> RegexExpression ::= 'REGEX' '(' FunctionOrVar ',' String ( ',' String )? ')'
> 
> 
> Considering that the spec is already in Last Call, I hope this comment
> doesn't come too late.
> 
> Regards,
> 
> Arjohn
> 

Arjohn,

I forwarded this to the working group with some discussion:
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006JanMar/0418.html

The working group discussed this but there was no enthusiasm for such a change.

For the query writer, trying to give some type safety at this one point when 
there is no just assurance from elsewhere in the grammar, did not seem like a 
significantly useful change.  The grammar would be noticeable more complicated 
because it isn't just FunctionOrVar each time but FunctionOrVar + appropriate 
kind of literal.

For the implementer, these built-ins still have to be able to deal with the 
full set of RDF terms being passed to one of the built-ins.

Any implementation can choose to issue warnings for this situation, or any 
other construction in a query, that the implementer wishes to bring to the 
application writer's attention.  Such a pass over the query after parsing is a 
  common way to do this rather than in the parser.


I hope this addresses your comment - please let us know if it does.  You can 
help our issue tracking system by prefixing the subject of your
response with [CLOSED] (where this subject has [OK?]).

	Andy
Received on Monday, 13 March 2006 14:58:30 GMT

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