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DAWG minutes 27 Jun 2006 for review

From: Dan Connolly <connolly@w3.org>
Date: Tue, 27 Jun 2006 11:09:04 -0500
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1151424544.16839.544.camel@dirk.w3.org>

Hypertext: http://www.w3.org/2006/06/27-dawg-minutes

plain text:

DAWG/SPARQL weekly
27 Jun 2006
Attendees
Present
        Kendall_Clark, DanC, PatH, FredZ, EricP, Jeen
Regrets
        AndyS, SteveH, EliasT, LeeF
Chair
        KC
Scribe
        DanC
Contents
      * Topics 
             1. Convene, take roll, review records and agenda
             2. Some proposed test cases
             3. optionals
      * Summary of Action Items

See also: IRC log


________________________________________________________________________
Convene, take roll, review records and agenda
-> DAWG minutes 20 Jun 

<kendallclark>
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0185.html

<kendallclark> Minutes from 20 June meeting

<kendallclark> PROPOSED to accept them as a record of last week's
meeting

<kendallclark> 2nd, DanC

<kendallclark> RESOLVED

KC: no meeting next week nor the rest of July...

PROPOSED: to meet 1 Aug...
... to meet 1 Aug 14:30Z, KC to chair...

EricP: I'm at risk for 1 Aug.

PatH: I'm at risk due to travel 1 Aug

FredZ: I'm at risk 1 Aug

KC: I'll find a scribe or something...

<kendallclark> RESOLVED

RESOLUTION: to meet to meet 1 Aug 14:30Z, KC to chair.


Some proposed test cases 
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0171.html 

<scribe> ACTION: FredZ to write an email w/ a test for the test suite
re: { P1 } UNION { P2 } OPTIONAL { P3 } [DONE] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action01]

PatH: I was surprised that putting a filter between two triples made
[missed]

FredZ: yes, that's why I'm raising it.

"3. Same dataset, slightly revised query:"

<kendallclark> That definitively raises (or reopens) some issue... Not
sure which.

<kendallclark> I mean, Fred's 3b test

several regard Fred's "3. Same dataset, slightly revised query:" as
surprising.

PatH: I think we discussed this and the scope of _:a is the {}s.

FredZ: that's not the way I read the definition of basic graph matching

EricP: is it enough to move the filters to the end?

FredZ: we could specify that, I suppose

<kendallclark> I don't recall discussing that at all...

(I have a vague memory of discussing it)

(darn; Fred just read from where in the spec?)

<kendallclark> Section 4.3...?

(the TOC seems to be hosed;
http://www.w3.org/TR/rdf-sparql-query/#matchDEntail doesn't got to 4.3)

FredZ: I see "Any solution for the group graph pattern that can satisfy
all the graph patterns in the group is valid, independently of the order
that may be implied by the lexical order of the graph patterns in the
group."

KC: that should be integrated with [missed], at least, yes?

EricP: so it should show up in a formal definition...?

<ericP> the extracted definitions

FredZ: I understood all the stuff outside the boxes to be commentary

<kendallclark> FredZ: Spell out more clearly how to apply 4.3

FredZ: consider { {?x <v1> _:a .} FILTER (isIRI (?x)) {?x <v2> _:a} }...
does 4.3 imply that you can erase the inner {}s?

EricP: doesn't the grammar make that clear? I guess there isn't a strong
statement about the connection to the grammar... would that help?

FredZ: indeed! that's been my main point

<kendallclark> i.e., asking that they be made more explicit

EricP: recall the A OPT B C OPT D thing... [?]

(EricP and FredZ discuss at a rate that exceeds the scribe's capacity)

<kendallclark> I'm prepared to make a new issue, evalOrder, to track
this bit... I think it's may be more than editorial.

PatH: the optional thing could be phrased more directly, [...], without
"otherwise"
... seems to me that the basic graph match semantics are attached to
GraphPattern, which includes FILTERs...

Jeen: how about just expanding the scope of blank nodes to the whole
query?

FredZ: that would be intuitive; it's a question of defining Basic Graph
Pattern matching so that it works...
... I'd prefer to introduce Existential quantifiers so that the user can
say what the scope is.

PatH: I take the spec to say that {}s do that now.

FredZ: OPTIONAL always has {}s around the 2nd arg... so it's different?
[?]

PatH: yes.

FredZ: users are going to find that a little wierd...

PatH: yes, users who aren't familiar with blank nodes are going to find
them wierd...

FredZ: the problem is that the RDF Primer explains blank nodes as a
solution to the problem that not everything is a binary relation...

<kendallclark> FredZ does a perfectly good impression of TimBL's
argument for Turtleization of our syntax! :)

FredZ: so [something about copy/paste and OPTIONAL and something
breaking, a very interesting case that I hope Fred or somebody will
capture in email]
... in SPARQL, ?var is like a forall in FOPC and _:var is like exists
FOPC... it would make sense to make the quantification scope explicit

PatH: it's explicit enough for me with the {}s

EricP: [something about SQL]... I don't see how SPARQL has
existentials...

PatH: a query is like a negated formula, so existentials act like
existentials

FredZ: I don't see the negation...

PatH: well, that's a simplification... the query is on the point end...
KB =?=> Query

FredZ: entialment is |=? why do we prefer that to |- ?

PatH: |= is logical entialment, |- is provability; semantic vs
syntactic...
... |= vs |- isn't the main thing; the main thing is just plain old
scoping

FredZ: I think having explicit existential quantifiers would help

EricP: FredZ, I'm not clear on what you're after; if there was just one
scope for blank nodes...

<FredZ> select ?x where { (exists _:a) ?x <v> _:a OPTIONAL { _:a <v1>
<b> }}

<ericP> apologies for not respecting the queue

DanC: I don't like having multiple scopes for blanknodes; I understand
this came from the rdfSemantics issue, when I was trying not to think to
hard about what I liked and what I didn't like

<kendallclark> I don't like that the people who seem to be thinking
really hard and deeply about this stuff don't agree!

PatH: I think the language currently has the expressiveness you're
asking for, without that syntax, Fred

<kendallclark> I'm not entirely sure that many of these semantic issues
matter; deciding one way or the other is often a coin toss. What's
especially troubling is that we don't seem to have a document that
reduces the choices sufficiently clearly enough. :<

<patH> fwiw, scoping bound variables is one of the very few things that
Alonzo Church got wrong in print.

<kendallclark> DanC: What's the cost of just making one scope for blank
node identifiers?

PatH: I don't think there's one best solution... every design has
something that looks broken...

<kendallclark> PatH: Seem to recall that it broke some folks intuitions
in some cases.

<ericP> ASK { GRAPH <x> { ?a ?b _:a } GRAPH <y> { ?x ?y _:a }

<ericP> }

what's complicated about that, ericP? there are other cases where it's
implementation-dependent whether parsing a file twice yields disjoint
bnodes or not

<LeeF> I've found the current bnode scoping to be very convenient when
writing code that generates SPARQL queries - clearly not a first-rate
argument in favor, but just a datapoint.

<patH> lee, that means you know what hte curent scoping is, right?

<LeeF> Yes, I know what the current scoping is.

<LeeF> At least, I'm pretty sure I know =)

<jeen> according to the spec it's the BGP. See section 2.8.3, first
line. right?

<LeeF> That's been my take on it.

<jeen> ...and according to section 2.5.4 the filter does not 'split' the
bgp. I think I'm lost about what the issue is ;)

KC: so yes, let's turn these test case sketches into test cases and
collect some data about how implementors have interpreted the spec

<patH> 2.8.3 first line says scoped to the *query*, not BGP.



<scribe> ACTION: EricP to turn FredZ's test case sketches into tests.
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0171.html
[recorded in http://www.w3.org/2006/06/27-dawg-minutes.html#action02]

<jeen> ah. I was looking the editor's draft patH

<jeen> my mistake

<patH> Ah, yes, I am behind current curve, thanks.

<patH> No, mine. Lets us use the absolutley most recent draft.


optionals
<scribe> ACTION: EliasT to turn C2.38 in PFPS's message into a test case
[CONTINUES] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action03]

(Elias might have done his part, but we haven't look at it)



<scribe> ACTION: KendallClark to reopen punctuationSyntax to take up
commas in SELECT clause. [CONTINUES] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action04]

<FredZ>
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0176.html

->
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0176.html
# formal semantics of OPT operator Fred Zemke (Friday, 23 June)

<LeeF> Elias says he did do his action and sent an email about it

FredZ: I wrote a proposal for semantics of OPTIONAL; Andy pointed out
that it didn't handle a case; indeed, he's right. 0176 is my reply at
that point

Fred: oops; typo in point 1; "S solves B, and there exists a restriction
of B that solves A." [scribe not sure he got that]

KC: I think Andy is working on edits in this area

FredZ: so the editor doesn't always wait for a WG decision?

KC: right; sometimes the WG makes a decision based on a proposal from
the editor

<kendallclark> I think we have significant schedule problems,
actually. :<

FredZ: hmm... schedule concerns... I'm less available in September

KC: acknowledged.

<kendallclark> PROPOSED to ADJOURN



<scribe> ACTION: DanC to review PFPS's comments for more test cases
[CONTINUES] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action05]



<scribe> ACTION: EliasT to respond to Mark Baker's comments re: MIME
type as we just resolved [DONE] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action06]



<scribe> ACTION: take up new issue concatenated nestedOptional
[CONTINUES] [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action07]


Summary of Action Items
[NEW] ACTION: EricP to turn FredZ's test case sketches into tests.
http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0171.html
[recorded in http://www.w3.org/2006/06/27-dawg-minutes.html#action02]
 
[PENDING] ACTION: DanC to review PFPS's comments for more test cases
[recorded in http://www.w3.org/2006/06/27-dawg-minutes.html#action05]
[PENDING] ACTION: EliasT to turn C2.38 in PFPS's message into a test
case [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action03]
[PENDING] ACTION: KendallClark to reopen punctuationSyntax to take up
commas in SELECT clause. [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action04]
[PENDING] ACTION: take up new issue concatenated nestedOptional
[recorded in http://www.w3.org/2006/06/27-dawg-minutes.html#action07]
 
[DONE] ACTION: EliasT to respond to Mark Baker's comments re: MIME type
as we just resolved [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action06]
[DONE] ACTION: FredZ to write an email w/ a test for the test suite re:
{ P1 } UNION { P2 } OPTIONAL { P3 } [recorded in
http://www.w3.org/2006/06/27-dawg-minutes.html#action01]
 
[End of minutes]

________________________________________________________________________
Minutes formatted by David Booth's scribe.perl version 1.127 (CVS log)
$Date: 2006/06/27 16:07:35 $ 

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Tuesday, 27 June 2006 16:09:14 GMT

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