-------- Original Message --------
> From: John Vandenberg <mailto:ja...@gm...>
> Date: 26 January 2006 11:50
>=20
> On 26/01/06, Seaborne, Andy <and...@hp...> wrote:
> >=20
> >=20
> > John Vandenberg wrote:
> > > Hi,
> > >=20
> > > I am trying to select a set of data out of a Mozilla extension
> > > install.rdf file. I am using SPARQL because it will be easy for
> > > developers to pick up and learn.
> > >=20
> > > My problem is that when an optional entry doesnt exist (iconURL),
> > > none of the fields are returned. This is the query I was trying
to
> > > perform.=20
> > >=20
> > > SELECT ?version, ?name, ?description, ?creator, ?icon WHERE (?x,
> > > <em:version>, ?version), (?x, <em:name>, ?name),
> > > (?x, <em:description>, ?description),
> > > (?x, <em:creator>, ?creator),
> > > (?x, <em:iconURL>, ?icon)
> > > USING em FOR <http://www.mozilla.org/2004/em-rdf#>
> > >=20
> > > To work around this, I am individually selecting each optional
piece
> > > of data. Can this be improved on?
> > >=20
> > > --
> > > John
> >=20
> >=20
> > That syntax is RDQL not SPARQL.
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> Sorry for the confusion; I am in the process of converting to SPARQL.
:-)
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> > That query exactly translated is:
> >=20
> > PREFIX em: <http://www.mozilla.org/2004/em-rdf#>
> >=20
> > SELECT ?version ?name ?description ?creator ?icon WHERE
> > { ?x em:version ?version ;
> > em:name ?name ;
> > em:description ?description ;
> > em:creator ?creator ;
> > em:iconURL ?icon .
> > }
> >=20
> > (Mechanical translation by program - but not a PHP program :-()
> >=20
> > and adding optional for iconURL:
> >=20
> > PREFIX em: <http://www.mozilla.org/2004/em-rdf#>
> >=20
> > SELECT ?version ?name ?description ?creator ?icon WHERE
> > { ?x em:version ?version .
> > ?x em:name ?name .
> > ?x em:description ?description .
> > ?x em:creator ?creator .
> > OPTIONAL { ?x em:iconURL ?icon . }
> > }
> >=20
> > a little more neatly that is:
> >=20
> > PREFIX em: <http://www.mozilla.org/2004/em-rdf#>
> > SELECT ?version ?name ?description ?creator ?icon WHERE
> > { ?x em:version ?version ;
> > em:name ?name ;
> > em:description ?description ;
> > em:creator ?creator .
> > OPTIONAL
> > { ?x em:iconURL ?icon .}
> > }
> >=20
> > Hope that helps,
>=20
> Yes, thanks. Am I right that RDQL does not offer similar
functionality?
RDQL does not offer such functionality.
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> Also, the docs say that SPARQL support in rdfapi-php requires php 5.1;
> are there specific problems that can be fixed or avoided in order to
> run it on a locked down Redhat ES3 box with php 4.3.2 ? =20
Sorry - I don't know. I can only answer SPARQL general questions.
Andy
>=20
> --
> John
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