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test cases for fromUnionQuery, please

From: Dan Connolly <connolly@w3.org>
Date: Tue, 31 May 2005 12:07:46 -0500
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1117559266.19175.72.camel@localhost>

So I was almost prepared to put the question ala:

  address fromUnionQuery ala http://www.w3.org/2001/sw/DataAccess/rq23/
  1.367 plus multiple FROMs allowed 

but I didn't put the question because discussion of other designs
didn't seem to be done. We ran out of time in the teleconference,
but now that I think about it, this design seems quite mature and
I wonder how we would get the other designs to be as mature; I haven't
seen proposed text for other designs; the 12 Oct spec didn't have
formal definitions; I didn't realize that people thought of it
as sharply different until today. It's understandable that other
people are counting on Andy to work out the details, since we're
all busy... but I think it's fair to ask for test cases.

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.


POLL OPTIONS:
  (0) take out GRAPH; query against one RDF graph punt SOURCE and
   fromUnionQuery issues

  (1) address fromUnionQuery ala
   http://www.w3.org/2001/sw/DataAccess/rq23/ 1.367 plus multiple
   FROMs allowed

  (1b) ala 1 but with no FROM/FROM NAMED in the QL, only in the protocol

  (2) use 12 Oct design
  (2b) ala PatH: bg graph always contains (vs is) the (er... something)

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

I'll give a few:

for (0), take out section "7 RDF Dataset" and "8 Querying the Dataset"
and "9 Specifying RDF Datasets" and cauterize dangling references;
similarly for the protocol spec. As for a test case, take all the SOURCE
tests and mark them as illegal syntax.

For (1), here's a test case that clarifies how multiple
FROMs work:

  SELECT ?who FROM <u1> FROM <u2> FROM <u3>
   WHERE { ?who foaf:knows :fred, :wilma, :barney }.

 <u1> has { :bambam foaf:knows :fred }
 <u2> has { :bambam foaf:knows :wilma }
 <u3> has { :bambam foaf:knows :barney }

I don't think (1b) has much/any support.

For option (2), I'm starting to understand how it's interestingly
different, but I'm not sure I have my finger on it. Would EricP
or SteveH or somebody please sketch a test case that makes the
difference crisp?

Also, Andy, can you take TimBL's comment
http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2004Nov/0020.html

and extract a test case that shows how the difference
between the 12 Oct design and what TimBL is asking for?


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.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
see you at XTech in Amsterdam 24-27 May?
Received on Tuesday, 31 May 2005 17:07:50 GMT

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