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Re: sparqlx

From: Kendall Clark <kendall@monkeyfist.com>
Date: Tue, 22 Mar 2005 15:02:25 -0500
To: "Seaborne, Andy" <andy.seaborne@hp.com>
Cc: DAWG Mailing List <public-rdf-dawg@w3.org>
Message-ID: <20050322200225.GA629@monkeyfist.com>

On Tue, Mar 22, 2005 at 06:06:25PM +0000, Seaborne, Andy wrote:

> I had a quick scan (and will look more later).   2 (related) comments:

Thanks for looking, Andy.

> 1/ the handling of optional by an attribute. It seem more systematic to 
> define a tag c.f.:

Hmm, perhaps. The element v. attribute thing is endless, of course, I
just thought that saying a thing is optional is an attribute of that
thing, rather than something that relates one or things together,
which is what a UNION is.

I think it's 12 of one, 15 of the other. -shrug-

> 2/ Basic patterns and triple patterns
> Something like { ?s ?p ?o } can be viewed as a single triple pattern or it 
> can be a single triple pattern in a group.  

Yes, I struggled with understanding this bit of the SPARQL
grammar. I'm not sure I favor one or the other ways of looking at it;
in my view, the XML serialization should definitely be the tail and
the end-user syntax should be the dog.

> The view as group-triples makes more sense to me because of the extension 
> to { ?s ?p ?o . ?a ?b ?c . } - that is a group of two triple patterns (a 
> basic pattern).


> If pattern-groups are the only thing that can have triple patterns then 
> there is no need for a schema to have to cope with triple pattern or group 
> at each point.
> pattern-groups also hold constriants, optional, GRAPHs.
> I think this is close to the examples - a bit further away from the schema 
> with it's tpattern and gpattern.

Sorry, I don't understand what you mean here.
> It does introduce an extra level of XML but it makes it much easier to 
> process because of the regularity.  In compensation, it loses an atrribute 
> and makes the schema simpler (less variability).

Loses the optional attribute you mean?

> The top of query is always a pattern-group (like the {} round a query 
> pattern in the human syntax).

Yeah, this is definitely the part of the grammar I had the most
trouble with (save for arbitrary expressions as constraints).

I'll rethink it again with yr comments in mind.

Received on Tuesday, 22 March 2005 20:06:20 UTC

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