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adding dawg:monotonicity and extensible data types to SPARQL query

From: Eric Prud'hommeaux <eric@w3.org>
Date: Tue, 15 Aug 2006 14:40:50 +0200
To: dawg mailing list <public-rdf-dawg@w3.org>
Message-ID: <20060815124050.GE6336@w3.org>

On Mon, Aug 14, 2006 at 01:08:03PM +0200, Eric Prud'hommeaux wrote:
http://www.w3.org/2001/sw/DataAccess/rq23/rq24#tests v1.14 has a new
draft of the Value Testing section. This does not include the
extensible datatypes support (but certainly makes it easier to add).
This version is intended to include only editorial changes from the CR
version.

>    [DONE] ACTION: EricP to respond to PatH's new test with a proof of
>    whether it's monotonic to extended datatype support [recorded in
>    [25]http://www.w3.org/2006/08/08-dawg-minutes.html#action01]

>    <fred> literal = literal: true or error
> 
>    <fred> iri = iri: true or false
> 
>    <fred> bnode = bnode: true or false
> 
>    <fred> allother cells always false
> 
>    2=3
> 
>    <AndyS> Yes, Fred - that's the table I was thing of.

In 1.14, I've updated RDFterm-equal to the following:

http://www.w3.org/2001/sw/DataAccess/rq23/rq24#func-RDFterm-equal
[[
Returns TRUE if term1 and term2 are the same RDF term as defined in
Resource Description Framework (RDF): Concepts and Abstract Syntax
[CONCEPTS]; produces a type error if the arguments are both literal
but are not the same RDF term; returns FALSE otherwise. term1 and
term2 are the same if any of the following is true:

    * term1 and term2 are equivalent IRIs as defined in 6.4 RDF URI
      References.
    * term1 and term2 are equivalent literals as defined in 6.5.1
      Literal Equality.
    * term1 and term2 are the same blank node as described in 6.6
      Blank Nodes.
]]

I added the "; produces a type error if the arguments are both literal
but are not the same RDF term; returns FALSE otherwise" bit. The rest
was already there.

>    <AndyS> bNode = literal (not bNode in query) may be valid
> 
>    <AndyS> Separate sameLiteral operator.
> 
>    <AndyS> if we want a syntactic comparision
> 
>    <AndyS> "(x,y)"^^:geo
> 
>    <AndyS> If you want help with this, do ask - I'm the one keen to have
>    this extensibility so I feel responsible here.
> 
>    <kendallclark> ACTION: EricP to redraft section 11 to support
>    extensible datatypes [recorded in
>    [18]http://www.w3.org/2006/08/08-dawg-minutes.html#action08]

To this end, I propose the following addendum to the derived types list:
[[
Extended SPARQL implementations may treat additional types as being
derived from numeric types.
]]

and a new minor section following the operator table:
[[
11.3.1 Operator Extensibility

Extended SPARQL implementations may support additional associations
between operators and operator functions; this amounts to adding rows
to the table above. No additional operator support may yield a result
that replaces any result other than a type error in an unextended
implementation. The consequence of this rule is that extended SPARQL
implementations will produce at least the same solutions as an
unextended implementation, and may, for some queries, produce more
solutions.
]]

I think this behaves exactly as sop:value-compare would.


Cost:

Is the cost of using the same operator for value comparison and symbol
comparison less than that of making users use a different operator for
RDFterm-equal? I think it's a matter of taste. The wierd case in this
solution is that you can't negate a syntactic literal equivilence
test.

Data:
  <x> <p> "II"^^roman:numeral .

Query1:
  ASK { ?x ?p ?v
        FILTER (?v = "IV"^^roman:numeral) }
Result1: no

Query1:
  ASK { ?x ?p ?v
        FILTER (?v != "IV"^^roman:numeral) }
Result1: no

Of course, and extended SPARQL implementation may give you a yes for
the latter but the issue that will make users cock their heads shows
up in the unextended implementation.

-- 
-eric

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Received on Tuesday, 15 August 2006 12:39:34 GMT

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