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Re: [Sesame-devel] Re: Semantic Web Phase 2 Activity - Protocol - Query Language

From: NMP-MSW/Tampere <patrick.stickler@nokia.com>
Date: Sun, 16 Nov 2003 10:40:13 +0200
Cc: Damian Steer <pldms@mac.com>, Jeen Broekstra <jeen@aduna.biz>, "Seaborne, Andy" <Andy_Seaborne@hplb.hpl.hp.com>, "'Steve Harris'" <S.W.Harris@ecs.soton.ac.uk>, www-rdf-interest@w3.org, sesame-devel@lists.sourceforge.net
To: "ext Arjohn Kampman" <arjohn.kampman@aduna.biz>
Message-Id: <7ED2A7F8-1810-11D8-B6EF-000A95EAFCEA@nokia.com>


On Friday, Nov 14, 2003, at 17:35 Europe/Helsinki, ext Arjohn Kampman 
wrote:

>> I should add that I did consider returning graphs rather than variable
>> bindings, which has the virtue that the results are
>> unambiguous. However this, in my case, was essentially useless as I
>> was trying to retrieve information from a graph, and returning a graph
>> seemed a little perverse.
>
> Amen. This is exactly why SeRQL offers both: you need table-like query
> results in the end because otherwise you stuck with graphs forever.
>

Well, for those manipulating the knowledge expressed in the
graph, one eventually needs a means of extracting particular
nodes, but I don't agree that that necessarily requires a table-like
query result. There are many ways to accomplish that in an API
without resorting to tables.

I'm not against variable binding tables. I use them daily. I just
wanted to point out that, since we're talking here within the
context of standardization and requirements, that how one
manipulates a graph returned as the result of a query need not
absolutely involve a table of bindings.

You're quite right that, at somepoint, you have to go beyond
the graph and get at the individual nodes. But tables are only
one way to do that.

I'd like to see the graph manipulation/consumption part left
out-of-scope by an RDF query standard so that APIs are free to
optimize as they like. There may later arise a standardized API
for manipulating RDF graphs, to aid in software portability
and integration (e.g. an RDF "DOM") but there is IMO no hard
dependency between a standardized language for expressing queries,
the execution of which returns subgraphs of the kb queried, and a
language for manipulating graphs to do particular things with particular
nodes.

I think the industry is well ready to standardize the former, but
not yet (if ever) the latter.

Cheers,

Patrick
Received on Sunday, 16 November 2003 03:43:04 GMT

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