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RE: SPARQL / Language spec ready for review [Howard's feedback]

From: Howard Katz <howardk@fatdog.com>
Date: Fri, 8 Oct 2004 10:46:36 -0700
To: "Eric Prud'hommeaux" <eric@w3.org>
Cc: "Dave Beckett" <dave.beckett@bristol.ac.uk>, "Dan Connolly" <connolly@w3.org>, "Andy Seaborne" <andy.seaborne@hp.com>, "Steve Harris" <S.W.Harris@ecs.soton.ac.uk>, "RDF Data Access Working Group" <public-rdf-dawg@w3.org>
Message-ID: <IKEOLCDFPBBPPAHGNKKOEEBGFAAA.howardk@fatdog.com>

Changes look good, Eric,

just two very minor comments:

1)  a TOC with bolded and non-bolded sections looks very odd to me. I don't
think I've ever seen that as a stylistic device. I'd kill the bolding.

2)  4.2 Multiple Optional Blocks, first sentence:

    "optionals blocks" -> "optional blocks"

Other than that, nice work!
Howard

> -----Original Message-----
> From: public-rdf-dawg-request@w3.org
> [mailto:public-rdf-dawg-request@w3.org]On Behalf Of Eric Prud'hommeaux
> Sent: Thursday, October 07, 2004 3:07 PM
> To: Howard Katz
> Cc: Dave Beckett; Dan Connolly; Andy Seaborne; Steve Harris; RDF Data
> Access Working Group
> Subject: Re: SPARQL / Language spec ready for review [Howard's feedback]
>
>
> Hi Howward, thanks for the feedback and many apologies for the delay
> in response.
>
> All issues should have responses here. Let me know if they are
> satisfactory, with special indication if they are not satisfactory for
> 1st WD.
>
> On Tue, Oct 05, 2004 at 07:12:27AM -0700, Howard Katz wrote:
> > Hi Eric,
> >
> > This is done off a fairly quick read. I haven't tried to correlate my
> > feedback against Dave's or anyone else's comments. I'm mostly
> *not* doing a
> > lot of nit-picking against spelling errors and other typos at
> this point,
> > ie, this is a bit of a higher-level view. This was reviewed
> against 1.82.
> >
> > Hope it's useful,
> > Howard
> >
> > ------------------------
> > 1 Introduction
> >
> > If you're having sub-headings, as in "Document Outline" and "Document
> > Conventions", wouldn't it be more consistent to sub-number
> them, as in "1.1"
> > and "1.2"?
> 1.97:
> Outline is gone. Convention is now section 1.1 and in the TOC
>
> > ---------------------
> > 2 Making Simple Queries
> >
> > Why not use the same data and query example(s) in the initial pictorial
> > section and the following SPARQL syntax section? That way
> readers would get
> > a better feel for how one form translates into the other.
>
> Nack. DanC and DaveB (I think) have suggested that we not use bNodes
> in the first example. Thus the SVG will have to be reworked so it's
> not worth bringing the following examples to convergence.
>
> > -----------------------
> > last paragraph
> >
> > Where doesn't the "andy" come from? I don't see him in the graph above.
> 1.97:
> [[
> ...known by Alice (specifically, the person with the mbox
> alice@work.example)
> ]]
>
> > ------------------------
> > 2.1 Writing a Simple Query
> >
> > Second paragraph, "The terms quoted ..."
> >
> > It's a fair distance from this sentence to the actual example
> below, and the
> > reader's eyes have to jump down to the example and then find
> their way all
> > the way back up again. Why not move this paragraph to either after the
> > "Data:" section or after the "Query:" section?
> 1.97:
> I didn't want to break up the association between Data, Query,
> Results, so I moved the explanation below the results. It's an after
> the fact explanation, but that may be clearer.
>
> > ----------------------
> > 2.2 Triple Patterns
> >
> > I'm not sure if this requires a bit of reorg or not, but all
> the examples in
> > the preceding section have WHERE clauses containing triple
> patterns, but you
> > don't introduce the concept until here.
>
> Nack. Yeah, but they don't know it yet. I think this is a fairly good
> solution to the usual tension caused by needing to introduce
> everything at once.
>
> > More importantly, you never say what a triple pattern IS (ie, something
> > along the lines of "A template for describing an s-p-o triple, with
> > variables representing missing information to be filled in by
> the query" or
> > some such. That would be very useful for reader.
> >
> > At a minimum, I'd change sentence one from
> > "The building blocks of queries are triple patterns"
> > to
> > "The building blocks of queries are triple patterns, shown as
> the arguments
> > of the WHERE clauses in the three queries in the preceding section."
> >
> > ---------------------
> > As well, a brief sentence explaining that triple patterns are
> delimited by
> > parentheses ("(" and ")") would be useful.
> 1.97:
> [[
> The building blocks of queries are triple patterns. Syntactically, a
> SPARQL triple pattern is a subject, predicate and object enclosed in
> '()'s. The previous example shows a triple pattern with a variable
> subject (book), a predicate of dcore:title and a variable object
> (title).
>
> ( ?book dcore:title ?title )
> ]]
>
> > --------------------
> > Paragraph 2, "A triple pattern has either a graph label
> (URIRef, literal) or
> > a named variable in each of the subject, predicate and object
> positions."
> > Literals of course can only go in the object position. Is it ok
> to be this
> > imprecise? (I'm asking because I don't know and don't have a strong
> > opinion.)
>
> Nack. (the question didn't result in a change of text.)
>
> A lot of people think that RDF triples should be fully
> symmetrical. I'm agnostic on this, but don't feel compelled to
> complicate the spec to reduce the expressivity to RDF. Model
> conformance can be enforced practically -- people generating queries
> will not see data that requires literals in the predicate or subject.
>
> > ----------------------
> > Definition: Triple Pattern
> >       "3" -> "three"
> ?.??:
> addressed by Andy's earlier changes to the defintion.
>
> > ----------------------
> > 2.3 Graph Patterns
> > First paragraph, "This starts with conjunction - the 'and' of triple
> > patterns."
> >
> > It's not clear what "This ..." refers to. How about something
> like, "We'll
> > first look at conjunctions, which combine triple patterns using "and".
> 1.97:
> [[
> The keyword WHERE is followed by a Graph Pattern which is made of one
> or more Triple Patterns. These Triple Patterns are "and"ed
> together. More formally, the Graph Pattern is the conjunction of the
> Triple Patterns. In each query solution, each triple pattern must be
> satisfied with the same binding of variables to values.
> ]]
> Better?
> Sort of an oversimlification (elides OPTIONALs and maybe ORs if they
> get in the lang).
> Good enough?
>
> > -----------------------
> > Paragraph starting "There are is a bNode ..."
> >
> > 1) "are is" -> "is"
> ?.??:
> Andy got it.
>
> > 2) I don't understand the final clause in second sentence: ", nor to any
> > query."
> 1.97:
> [[
> There is a bNode [12] in this dataset. Just within the file, for
> encoding purposes, the bNode is identified by _:a but the information
> about the bNode label is not in the RDF graph. No query will be able
> to identify that bNode by name.
> ]]
> I wrestled with "identify that bNode by the name _:a" but it seemed
> worse.
>
> > ------------------------
> > 2.4 Multiple Matches
> >
> > "The results of query" -> "The results of a query"
> 1.97:
>
> > ------------------------
> > 4.2 Multiple Optional Blocks
> >
> > Second paragraph, you introduce the concept of outer block.
> This hasn't been
> > previously discussed, so it's unclear what this refers to.
> Please define. As
> 1.97:
> [[
> In this example, there are two, independent optional blocks. Each
> depends only on variables defined in the non-optional part of the
> graph pattern.
> ]]
>
> > well, you follow with a hypothetical, "If a new variable is
> introduced in an
> > optional block ...", a short "WHERE" snippet example showing
> this would be
> > very helpful.
> 1.97:
> wordsmithed text to show it from the previous example
> [[
> In this example, there are two, independent optional blocks. Each
> depends only on variables defined in the non-optional part of the
> graph pattern. If a new variable is introduced in an optional block
> (as mbox and hpage are introduced in the previous example), that
> variable can be bound in that block and can not be mentioned in a
> subsequent block.
> ]]
> Slightly awkward, but an improvement in clarity, I think.
>
> > ------------------------
> > 4.3 Optional Matching
> >
> > Is there a new syntactic feature introduced here? If so, an
> example would be
> > helpful.
> 1.97:
> This section is a definition for the syntactic feature introduced
> in 4.1 by
> [[
> Optional portions of the graph may be specified in either of two
> equivalent ways:
> ]]
> I changed the titles around to reflect that:
> s/4.3 Optional Matching/4.3 Optional Matching -- Formal Definition/
> s/4.1 Optional binding/4.1 Optional Matching/
>
> > ------------------------
> > 5 Nested Patterns
> >
> > It would be useful to introduce this section with a brief explanation of
> > what nesting is. Ie, What is its purpose? Why is it useful?
>
> Nack. Punting. I want to wait until the WG decides whether to include
> OR in the language before attacking this.
>
> > ------------------------
> > Final example in section:
> >
> > I don't see a correspondance between the arguments of the
> SELECT statement
> > and the headings in the result table. "mbox" would have to be
> SELECTed to be
> > output, wouldn't it, and what happened to "name"?
> 1.97:
> changed SELECT to make example internally consistent (and still sensible)
> [[
> SELECT ?foafName ?mbox ?fname ?gname
> ]]
>
> > ------------------------
> > 8 Choosing What to Query
> >
> > Third paragraph, "To execute a query, there needs to be the
> query and an RDF
> > graph."
> > Awkward. How about: "Query execution requires both a query and an RDF
> > graph."
> 1.97:
> [[
> A SPARQL query must be executed against some real or virtual RDF
> graph.
> ]]
>
> > -------------------------
> > 9 Querying the Origin of Statements
> >
> > I realize you have a footnote on the first sentence saying the
> semantics are
> > undefined, but how about at least a very loose explanation of
> what a SOURCE
> > is in the paragraph itself, so the reader at least has a rough idea of
> > you're talking about? Maybe the footnote could be reworked and
> moved into
> > sentence number two? Ie, something like (I'm not claiming this is
> > technically accurate):
> >
> > " ... many RDF data stores augment this with the source of each
> statement.
> > Source is at present undefined, but is expected to refer in some
> > implementation-dependent way to the document of origin,
> possibly given by a
> > URL."
> >
> > or some such.
> 1.97:
> I hit it with my (real or virtual) real-or-virtual hammer.
> [[
> While the RDF data model is limited to expressing statements with a
> subject, predicate and object, many RDF data stores augment this with
> a notion of the source of each statement. Typically,
> implementations associate RDF triples or graphs with a URI specifying
> their real or virtual origin.
> ]]
>
> > ------------------------
> > 10 Summary of Query Patterns
> >
> > Does the bullet "disjunction" correspond to the "alternatives"
> mentioned in
> > "6 More Pattern Matching - Alternatives"?  I don't know the ultimate
> > dispostion of this section but suggest if it stays and is
> mentioned in this
> > list, that the terminology be made consistent.
> ?.??:
> That reference, and the whole neighborhood, was wiped out by
> Hurricane Andy.
>
> > ------------------------
> > 11.2 Constructing an Output Graph
> >
> > I'm confused by the three boxed snippets. #3 is labelled
> "Example" -- are
> > the first two NOT examples as well? What distinguishes #3 from
> #1 and #2?
> >
> > Also, #3 has "PREFIX . . . CONSTRUCT". Are the ellipses part of
> the syntax??
> ?.??:
>
> > --------------------------
> > 11.4 Asking "yes" or "no" questions
> >    -> 11.4 Asking "Yes" or "No" Questions
> >
> > I'd also invert sentence #1 and tighten a bit:
> > "In order just to test whether a query pattern has a query
> solution or not,
> > the application can use the ASK form."
> >    ->
> > "Applications can use the ASK form to test whether a query pattern has a
> > solution or not."
> 1.97:
> [[
> Applications can use the ASK form to test whether or not a query
> pattern has a solution.
> ]]
>
> > ------------------------------
> > 12.1 Standard Operations
> >
> > "The SPARQL language provides some of the operations on plain
> literals, XSD
> > integers and XSD floats taken from those in XQuery and XPath
> Functions and
> > Operators <http://www.w3.org/TR/xpath-functions/>."
> >
> > A bit awkward. Do you mean:
> >
> > "The SPARQL language provides a subset of the operations on
> plain literals,
> > XSD integers and XSD floats defined in XQuery and XPath Functions and
> > Operators <http://www.w3.org/TR/xpath-functions/>."
> 1.97:
> verbatim
>
> --
> -eric
>
> office: +81.466.49.1170 W3C, Keio Research Institute at SFC,
>                         Shonan Fujisawa Campus, Keio University,
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>
> (eric@w3.org)
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Received on Friday, 8 October 2004 17:44:52 GMT

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