Re: Operational definition of SPARQL algebra

On 20 Oct 2006, at 14:18, Seaborne, Andy wrote:

>
> No need for Chilean proposal 4 for additional restrictions - which  
> I feel is
> too strong anyway (example below):
>
> SELECT *
> {
>     ?x rdf:type skos:Concept .
>     OPTIONAL { ?x skos:prefLabel ?label }
>     OPTIONAL { ?x skos:altLabel  ?label }
> }
>

For the record, I'm still very much against this kind of construct  
(variables that appear only in OPTIONAL and appear in > 1 OPTIONAL).  
I think it's not at all clear what it means (to humans) and adds an  
unnecessary implementation burden.

I'm guessing that the example given above is just a hack to get round  
the fact that we can't do SELECT COALESCE(?refLabel, ?altLabel)?

- Steve