W3C home > Mailing lists > Public > semantic-web@w3.org > July 2006

RE: baseURI - SPARQL endpoint - Named Graph

From: Hans Teijgeler <hans.teijgeler@quicknet.nl>
Date: Wed, 5 Jul 2006 19:39:02 +0200
To: "'Richard Newman'" <r.newman@reading.ac.uk>
Cc: "'SW-forum'" <semantic-web@w3.org>, "'Paap, Onno'" <onno.paap@gmail.com>, "Benjamins, Robin" <rxbenjam@bechtel.com>
Message-ID: <001201c6a059$eb485f00$6c7ba8c0@hans>
Hi Richard,
Thanks for your quick response!
We will have, in due course, groups of hundreds of quad stores that contain
information about a large project (like building a chemical plant). These
are then owned by many companies and departments in those companies around
the globe, directly or indirectly involved in that project.
The data in a quad store has been mapped from some application to the ISO
15926 format, and is owned by the owner of the quad store. All other data
must be fetched from the other stores.
Each quad store has its own SPARQL endpoint, and its own base URI (but we
don't know whether that base URI is necessary for that endpoint or not)
We use RAP, because PHP is ubiquitous on the Internet, not so Java (alas).
These hundreds of standardized quad stores must be cheap, any mom-and-pop
shop must also be able to afford it. For larger data sets we will advise to
go to one of the Java stores that are on the market (if they can support
Named Graphs).
RAP supports Named Graphs, and now the plot thickens.... How does that
relate to the endpoint and the base URI of that same store? For your
information: we intend to (mis?-)use the Named Graphs for a
compartimentation of the quad store, e.g. import archive, export archive,
population archive, handover archive, and of course the actual 'payload'
information content.
One last question: is there a mandatory format for SPARQL endpoints? Can
these two endpoints co-exist:  

HYPERLINK "http://www.pqr-ltd.com/p4502/me03"http://www.pqr-ltd.com/p4502/

"http://www.pqr-ltd.com/p4502/me03"http://www.pqr-ltd.com/p4502/me03  ?

Is that last slash '/' required?


From: Richard Newman [mailto:r.newman@reading.ac.uk] 
Sent: Wednesday, July 05, 2006 18:56
To: Hans Teijgeler
Cc: SW-forum; Paap, Onno
Subject: Re: baseURI - SPARQL endpoint - Named Graph

The base URI is a URI that is used to resolve a relative URI during parsing
of a SPARQL query. 

A SPARQL endpoint is a service to which you can send protocol requests. This
is identified by a URI.

A named graph is a collection of triples identified by a URI.

You can, if you wish, have a SPARQL service at <HYPERLINK
"http://example.com/"http://example.com/>, use that as your base URI, and
have all of its triples stored in a graph named by that URI. That sounds
like the situation you're talking about.

More likely, you'll have no base URI (that's imposed by someone writing a
query), a SPARQL endpoint of something like <HYPERLINK
"http://example.com/sparql/"http://example.com/sparql/>, and be storing
things in named graphs like <HYPERLINK
"http://example.com/data/hans/"http://example.com/data/hans/>. The
commonality comes from owning the domain.

Can you be more specific?


On  5 Jul 2006, at 9:22 AM, Hans Teijgeler wrote:

Even after reading all sorts of documentation we keep being puzzled about
the real difference (if any) between:

*	base URI 

*	SPARQL endpoint 

*	Named Graph

If we keep them the same our stuff works, but we would like to know for 100%
why, so what the relationships between these three concepts are.
Anybody out there who can shed some light on this?

No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.9.9/382 - Release Date: 04-Jul-06

No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.394 / Virus Database: 268.9.9/382 - Release Date: 04-Jul-06
Received on Wednesday, 5 July 2006 17:39:43 UTC

This archive was generated by hypermail 2.4.0 : Tuesday, 5 July 2022 08:44:57 UTC