Re: [Rdfapi-php-interest] ORDER BY (different data types)

[Seaborne, A. <and...@hp...>]

-------- Original Message --------
> From: Christian Weiske <mailto:cw...@cw...>
> Date: 23 January 2007 15:41
>=20
> Andy,
>=20
>=20
> > The ordering of unlike things is partially defined in SPARQL.  I'm =
not
> > sure what your DB schema is but if the type of the node (URI, bnode,
> > datatype of literal) is some carefully choosen integer then
> >=20
> > ORDER BY ?emp
> > is (nearly)
> > ORDER BY emp.type, emp.lexicialform.
>=20
> I doubt that I can change the schema since many other parts of rdfapi
> use it.=20

That makes it tricky - isn't there a singel abstraction layer that =
handles all RDF->DB mapping?

If so, maybe adding a field to help SPARQL is an option.

>=20
>=20
> DB schema:
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> Field 	   Type
> -----------------------
> modelID    bigint
> subject    varchar(255)
> predicate  varchar(255)
> object     text
> l_language varchar(255)
> l_datatype varchar(255)
> subject_is varchar(1)
> object_is  varchar(1)
>=20
>=20
> subject, predicate and object values are stored in the corresponding
> fields. subject_is and object_is determine the overall type of the
> data: literal, resource, blank node.=20
> l_datatype is the real data type of the object, e.g.
> "http://www.w3.org/2001/XMLSchema#integer".
>=20
>=20
> By the way, how does jena do it (assuming you are coming from there)?

Only sort-of coming from there.  I was recalling what 3Store did as =
well.

The new Jena DB layer has a schema (actually, choice of schemas) =
specifically for SPARQL so we can store the sort type code.

ARQ currently does it all client-side because the objective is to be =
correct, corner cases of XSD datatypes and all.

	Andy

>=20
> --
> Regards/Mit freundlichen Gr=FC=DFen
> Christian Weiske