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Re: test cases for fromUnionQuery, please

From: Yoshio FUKUSHIGE <fuku@w3.org>
Date: Wed, 1 Jun 2005 20:27:32 +0900
Message-ID: <002c01c5669c$e6e5d340$f1e41b85@steelball>
To: "RDF Data Access Working Group" <public-rdf-dawg@w3.org>


Hi,

Dan:

> For each of these options, and any other designs anybody wants
> the WG to consider, would you please send a test case that
> distinguishes it from the design in the editor's draft?
> Bonus points for suggesting textual changes.

>  (3) ala Yoshio, no implicit dataset; all data to be queried
>  is specified in the query

> For (3), we one degenerate test case that distinguishes it
> from rq23 is the 1st example in the spec:
>
> SELECT ?title
> WHERE  { <http://example.org/book/book1>
> <http://purl.org/dc/elements/1.1/title> ?title }
>
> that becomes illegal. Some specification of the data
> to query is required; so the "hello world" example
> would change to semething like:
>
> SELECT ?title FROM <books.rdf> WHERE { ?book dc:title ?title }.
>
> That seems like a significant change in direction, so
> I'd like to see explicit support from several WG members
> before we explore it further.
>
> Other things that become illegal in this design are answers
> that come from beyond the graphs given in the query. I doubt
> that can be expressed in our current test harness, but I suppose
> we could figure out some way to do it.

Hmm, I don't see it significant change.
It's a design preference (EricP showed me in personal communication
that using (1) or (2), we can still do the same thing as (3),
but the query gets quite complicated).
It's a simplification.
(putting aside (0), it's the simliest one, I admit, but weaker)

Well, you don't have to be precise/complete when you don't care
what data the service use.

You can put the URI of the endpoint there in those cases, like
---
FROM <http://sparql.example.org/> # meant to have single <>'s
SELECT ...
WHERE {...}
---
where the URI of the endpoint of the service is http://sparql.example.org/

And the service may well use any inference or consulting any databases
(it's delegated)

This design is also useful especially when queries are handled by an 
intermediate
server, as Pat mentioned yesterday.

Query issuer (=end user) doesn't have to care about the protocol, he/she can 
let the system care.
Intermediator can delegate to some other service(s) safely, while keeping 
the query unchanged.


OK, test case, anyway

PREFIX foaf:    <http://xmlns.com/foaf/0.1/>
FROM <http://db1.example.org/>
SELECT ?m
WHERE {<http://example.org/People/Yoshio> foaf:mbox ?m}

Suppose this query is handled to SPARQL service A, whose endpoint URL is 
http://sparql.example.org/,
and A has access to some RDF databases identified by http://db1.example.org/ 
(db1), and http://db2.example.org (db2).

Suppose further that db1 has
<http://example.org/People/Yoshio> foaf:mbox <mailto:yoshio@example.org>.

and db2 has
<http://example.org/People/Yoshio> foaf:mbox <mailto:tonto@example.org>.


With option (3), only <mailto:yoshio@example.org> will be bound,
while in (1) or (2), when db2 is already in the default database,
<mailtp:tonto@example.org> will also be bound to ?m.

# And I don't want to be known my secret, i.e. being  "tonto" : )

I hope it will do as a test case.

Best,
Yoshio
fukushige.yoshio@jp.panasonic.com
fuku@w3.org
Received on Wednesday, 1 June 2005 11:27:34 GMT

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