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[Bug 10368] New: [XQuery11] review of appendix C re scope of components

From: <bugzilla@jessica.w3.org>
Date: Sat, 14 Aug 2010 18:48:50 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-10368-523@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10368

           Summary: [XQuery11] review of appendix C re scope of components
           Product: XPath / XQuery / XSLT
           Version: Member-only Editors Drafts
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: XQuery 1.1
        AssignedTo: jonathan.robie@redhat.com
        ReportedBy: jmdyck@ibiblio.org
         QAContact: public-qt-comments@w3.org


(This comment is basically my message
http://lists.w3.org/Archives/Member/w3c-xsl-query/2010May/0041.html
from 2010-05-03.)

Here are my comments, all editorial...

> [Definition: The *scope* of a component is the context in which
> the  component is associated with a value.]

(1)
Is this using "context" in the sense of "static or dynamic context"? If 
so, it doesn't make much sense. For the most part, any given component is 
associated with a value in *every* static/dynamic context, so talking 
about *the* context in which this occurs is probably a mistake.

Or, if you mean "context" in some other sense, that's probably not a good 
idea, since Appendix C is almost entirely about static and dynamic contexts.


> [Definition: If a component has *global scope*, then every expression
> in the query has the same value for that component, and it can not be
> overwritten by the query module or by an expression.]

(2)
The phrase "every expression ... has the same value" is a garden path: it 
   may mislead the reader into thinking that you're talking about the 
value of an expression. I suggest that, throughout this appendix, instead 
of talking about the *value* of a component, we use some other word, e.g. 
"setting". (This is appropriate, because a component's setting is in 
general not an XDM value.) And/or we could alter the syntax somewhat, e.g.:
     ... then the [value/setting] of that component is the same
     for every expression in the query ...

(3)
The "and" in "and it can not be overwritten by the query module or by an 
expression" suggests that this clause is saying something new, but in 
fact it's a logical consequence of the preceding clause.

(4)
The phrase "query module" is undefined. I think it's (currently) used to 
mean "module", but I think readers might take it to mean "main module" 
(because that's the module that "contains the query"). I think we should 
avoid it. Instead, just say:
     "by any module or expression"

(5)
(Speaking of "query module", it looks like the thread I started at
http://lists.w3.org/Archives/Member/w3c-xsl-query/2010Feb/0007.html
never really got resolved.)

(6)
(There's also an occurrence of "query module" in 4.12.3 that should just 
be "module".)


> [Definition: If a component has module scope, then every expression
> in a given module has the same value for that component, and it can be
> overwritten or augmented for a given module.]

(7)
Instead of talking about overwriting or augmenting, maybe say something like:
     "but that value [setting] may differ between modules"


> [Definition: If a component has lexical scope, then it is defined by
> a query expression, and its scope is defined by the semantics of the
> expression that defines it.]

(8)
You're saying that a component is *defined by* an expression. I'm 
inclined to say that context components are defined by section 2.1 
[Expression Context].

(9)
The phrase "defined by a query expression" prompts the question "Which 
query expression?", which I don't think is what's wanted. Maybe
     "set by certain kinds of expression"
would be better. (It prompts the question "Which kinds?", which has a 
good answer, although we don't currently give it.)

(10)
By the way, I suggest changing "query expression" to just "expression".

(11)
It's odd for the definition of "lexical scope" to say that "its scope is 
defined by [something else]". That's getting into another (more 
conventional) meaning of "scope", which I think muddies the waters.

(12)
This definition diverges from the pattern set up by the previous 
definitions. A more consistent one would be something like:
     [Definition: If a component has lexical scope, then the setting
     of that component is fixed for any given expression, but may differ
     between expressions in the same module.]


> [Definition: If a component has dynamic scope, then it is defined by a
> query expression, its scope is defined by the semantics of the expression
> that defines it, and run-time evaluation may influence its value.]

(8, 9, 10, 11 again)
As above re "defined by a query expression" and "its scope is defined".

(13)
We should probably delete "run-time", as its presence might suggest an 
distinction from compile-time evaluation, which we don't intend.

(14)
A more consistent definition would be something like:
     [Definition: If a component has dynamic scope, then the setting of
     that component may differ between the contexts of a single
     expression.]

----

(15)
As I said here:
http://lists.w3.org/Archives/Member/w3c-xsl-query/2010Mar/0189.html
I think we should replace occurrences of "scope" in Appendix C with a 
different word. There I suggested "range" or "ambit". Now, I think I'd 
prefer something like "constancy" or "changeability". E.g.:
     [Definition: The *constancy* of a component indicates (roughly)
     the set of [static or dynamic] contexts in which that component
     has a common setting, or conversely, the level of granularity at
     which the setting of that component may differ between contexts.]

----

(16)
(Note that all of the above is independent of the other issue that it got 
tangled up with, namely that the spec is inconsistent on whether a module 
has a static context. I bring it up just so it doesn't get forgotten.)

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Received on Saturday, 14 August 2010 18:48:54 UTC

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