When to use sp:as?

[Mark Hale]

Hi all,

In the sp spec http://spinrdf.org/sp.html it mentions using sp:as in select clauses (section 4.2). There is no example, but it seems like it would look like this:

[ 
      sp:as [ sp:varName "result"^^xsd:string ] ;
      a       sp:Count ;
      sp:expression [
              sp:varName "object"^^xsd:string ;
      ] ;
]

On the other-hand the spl rdf file makes no use of sp:as and instead uses an alternative notation:

          [
            sp:expression [
                rdf:type sp:Count ;
                sp:expression [
                    sp:varName "object"^^xsd:string ;
                  ] ;
              ] ;
            sp:varName "result"^^xsd:string ;
          ]

Which should I be using?

[Holger Knublauch]

Hi Mark,

the spec is indeed ambiguous on this, and my recommendation would be to use whatever convention the SPIN API uses, because it is very unlikely that I'd introduce a change that would break deployed SPIN RDF files. This also makes it easier to generate SPIN RDF triples - just enter them in TBC and look at the produced source code.

I believe in the original design I was handling aggregations differently from other projection expressions such as SELECT (1 + 2 AS ?result) while in fact they should be treated uniformly. The sp:varName solution does just that and should be preferred over sp:as. I have dropped sp:as from the spec at spinrdf.org for now.

Thanks for pointing this out!
Holger

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