Daniel Schwabe wrote:
Kingsley Idehen wrote:
Pierre-Antoine Champin wrote:
I would expect that a DESCRIBE query to the SPARQL endpoint return what
I get when dereferencing the URI.
pa
Daniel,
Is this your problem:
Linked Data Servers publish URIs. The mechanism that delivers these
URIs tends to vary since they are the product of URL-rewrite rules
that may or may not be associated with SPARQL queries, and when
SPARQL Query based you may be dealing with a CONSTRUCT or a DESCRIBE.
If a URI actually refers to an RDF document, I would imagine there is
no URL rewriting involved; it resolves to the document itself.
On the surface yes, but not necessarily under the covers. For instance,
in Virtuoso we have virtual WebDAV resources and most of the time this
is what you are interacting with when you request an RDF information
resource (we call these DETs - Dynamic Extensions Types for our WebDAV
implementation).
And for SPARQL based, who knows what I may be dealing with? Peter
already exemplified that you may get something that is neither a
CONSTRUCT nor a DESCRIBE...
Ideally, you would like to be able to discern via SPARQL, what SPARQL
query patterns sits behind the re-write rule for a given
de-referencable URI.
Basically yes, although I'm not even requiring being able to do it
directly via SPARQL (that would be actually nice)...
If you can describe a SPARQL Query in RDF, it can be done. SPIN from
TopQuadarant [1] does have a specification for doing just that.
Also, I'd be curious to know what is more efficient - dereferencing or
issuing the query through the endpoint.
Depends, in the case of Virtuoso you're talking different paths to the
same mechanics i.e. a SPARQL Query and information resource caching schemes.
Links:
1. http://spinrdf.org/sp.html
Kingsley
Cheers
D
--
Regards,
Kingsley Idehen Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO
OpenLink Software Web: http://www.openlinksw.com
