RE: [Sparql4j-devel] Design issue: datasource

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

-------- Original Message --------
> From: Alberto Reggiori <>
> Date: 20 January 2005 10:36
>=20
> On Jan 20, 2005, at 10:04 AM, Janne Saarela wrote:
>=20
> > > > I would like to propose the datasource for this driver to be
> > > >=20
> > > >
jdbc:sparql4j:[http|other]://www.serveraddress.com[:port]/path/more;
> > > > param1=3Dvalue1
> > >=20
>=20
> [...snip...]
>=20
> > > Hmm, - actually there is a level missing.  We need something like:

> > > jdbc:sparql4j:sparql (yuk - 2 sparql's) to say:
> > > jdbc:sparql4j
> > >   Get JDBC to route requests to our driver
> > > jdbc:sparql4j:sparql
> > >   our driver is going to use the SPARQL protocol
> > > jdbc:sparql4j:sparql:http://server/path
> > >   our driver is going to use SPARQL protocol at the named service
> > > May be that's excessive.  An alternative is to not have sparql4j
be
> > > the subprotocol name and directly name the connection protocol:
>=20
> and we have to keep inmind that URIs has generally a <4k max size (or
> the network/firewalls might limit that) - and we want to be sure that
> those "connection" parameters are not too verbose (I would be in favor
> or k/v paris vs. full blown URIs if not necessary)

Agree about 4k - there are some 1k limits in old proxies I gather (never
met one myself).

Connection URL and service request URL are different.

In my quick-hack driver, I found the javax.sql.DataSource interface
useful - the service description can be passed in there.  To stick to
java.sql, then a nasty encoding into the JDBC URL (which is unpacked by
the driver (never leaves the machine - no 4k limit).

c.f. the JDBC-ODBC bridge where the driver takes params.=20

>=20
> > I'm wondering what happens if the sparql protocol enables short
names
> > in the 'lang' attribute value, will the datasource effectively have
> > to be something like=20
> >=20
> > jdbc:sparql:http://server/queryprocessor?lang=3Dsparql
> >=20
> > This would mean any service description part of the protocol would
> > need to be available before an application is built.
>=20
> what do we mean for "service description" ? I hope not the WS XML
world
> meaning of it - or even worse OWL-S :)
>=20
> Default is SPARQL (no lang param) - otherwise specified


That seems to be the way the F2F was going but we have to await draft
text to be sure.  It's all very fluid.

>=20
> > A datasource such as
> >=20
> > jdbc:sparql:http://server/queryprocessor
> >=20
> > would effectively have to fetch a service description before
launching
> > the first query in order to determine the 'lang' value. Luckily that
> > value should be cacheable not having to fetch it before every single
> > query.
>=20
> also me worried about how to process that "service description" - I am
> digging into JDBC3.0 spec chapter 7 (Database Metadata) and other
> implementations around - which has some methods to  retrieve general
> information about the data source - not sure how much flexible
> though...

Good point.  java.sql does rather prescibe the DB details but something
might be workable.

>=20
> Alberto

	Andy