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[GRAPH] graph deadlock?

From: Ivan Herman <ivan@w3.org>
Date: Sat, 17 Dec 2011 16:37:01 +0100
To: W3C RDF WG <public-rdf-wg@w3.org>
Message-Id: <3816B398-DC0A-4E43-8ABF-A4D8E861B596@w3.org>
(I am still on sick leave and will stay for a few more weeks. But I am emerging from my torpor, and what better way of doing that is to read through a thread on named graphs?:-)

I have gone through the thread of the past few days, and I have this feeling of déjà vu. Although there are some neat things that came up (I like Sandro's GSR-s), I have the impression that we are in a deadlock.

Maybe we have to accept the deadlock and move on from there. Namely: I have the feeling that we have two notions here, and the group (and the community, probably) is just too divided to reconcile those. So, maybe, we have to accept that we have two distinct notions here; we should document both in the RDF concepts, and try to live our lives. The two notions that I see are

(1) RDF Datasets. It consists of labelled graphs: (G, l), where l is an URI. (Some raised the possibility to use literals for 'l', but I think there is a consensus to use URI-s). There is no semantic relationship between 'G' and 'l', so something like (with an ad-hoc syntax here):

   ( {a:b c:d e:f}, mailto:ivan@w3.org }

is a perfectly o.k. labelled graph in an RDF Dataset

It seems that most (all?) quad stores fall into this category as well as the datasets in SPARQL

(2) Named Graphs. It is a special RDF dataset, where the label 'l' is a (HTTP?) URI with an additional behaviour: if that URI is poked (GET-d) then it results in the serialization of a Graph whose parsing yields an equivalent graph to 'G'. It is the right/good framework for, say, Linked Data, etc.

Obviously, details are to be filled in.

My impression is that some in the group (Richard? SteveH?) would like to have only (1), whereas others (Sandro, Pat?, TimBL?) would like to have only (2). This has been the core of the discussion for 6 months. Let us face it, we will _not_ have a consensus here. 

Is it so bad if we acknowledge this, and we clearly document the two notions? Both notions can be documented in RDF Concepts, maybe some (although I am not sure) in the RDF Semantics. We may think about some extra RDF relations among probably named graphs (sub-graph, things like that) which probably do not make too much sense for labelled graphs. In any case, as long as things are clearly defined, implementations, applications, etc, may decide what they do, what they expect, etc, and that is fine for interoperability.

I am not sure how this affects serialization.



Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Saturday, 17 December 2011 15:37:09 UTC

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