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[Admin PS] Presentation Task Force telecon Nov. 21 - cancelled

From: Chris Welty <cawelty@gmail.com>
Date: Fri, 21 Nov 2008 10:31:32 -0500
Message-ID: <4926D454.2070203@gmail.com>
To: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>


All - I forgot to send out the agenda/reminder for a PS TF telecon and I can't 
make it today anyway.  I spoke to a couple of you who also had forgotten about 
it (we did discuss at the last telecon to have one this week).

So, cancelled for this week.  I will try to send out a summary of the issues so 
we can progress by email.  Sandro indicated he *can* make a telecon next Friday 
- it's a major holiday in the US so many of us won't - is there anyone else who 
can make it next Friday?  Otherwise we'll have the next meeting on the 5th.


-Chris


Hassan Ait-Kaci wrote:
> Hello,
>
> This is an update on my on-going efforts to produce a working parser and
> XML serializer for the BLD Presentation Syntax: Action 564, due on
> October 31, 2008 (http://www.w3.org/2005/rules/wg/track/actions/564).
>
> I had already produced such a thing for the original specs - i.e., before
> several changes were made that have had the effect of introducing several
> rather nasty ambiguities and context sensitivity, both at the lexical and
> syntactic levels - even just for the canonical PS (i.e., even w/o the DTB
> shortcuts and Adrian's Abridged PS).
>
> I have been struggling trying to find workarounds to whatever snags have
> popped up whenever I could figure any. However, there still remain some
> tricky situations that require our attention (at least so that we produce
> specs that are not so uselessly complicated to implement without ad hoc
> hacks).
>
> It would be good that the PS Task Force convene sometime soon to discuss
> these issues and how to resolve them.
>
> Here are some examples of what I have puzzled over (this is non exhaustive):
>
> 1) Tokenizing the argument of the Prefix and base directives is made
>    uselessy complex by not enclosing the IRI in double quotes (viz., it
>    forces a lexer to *parse* IRI's - as opposed to just read them off -
>    for no purpose whatsoever, making the lexical nature of some characters
>    context-sensitive (for example, ':' is used as a delimiter for CURIE's
>    but not within IRI's; or, '#' is used as class membership, but not
>    within IRI's; etc, ...).
>
>    A possible workaround is simply to double-quote them in the directives.
>
> 2) The minus sign ('-') now appears in some identifiers (e.g., ?diffdays =
>    External(func:days-from-duration(?diffduration)). This would be no
>    problem if we just considered '-' to be part of identifiers like '_',
>    but it must also be seen as a literal character in order to recognize
>    tokens such as "->" and ":-". While this is not a major hitch, it is
>    unnecessary. (Not to mention the fact that '-' is the subtraction
>    operator in the APS.)
>
>    A possible workaround is simply to disallow '-' in identifiers (say,
>    using '_' instead) - as is the case in most programming languages.
>
> 3) The ANGLEBRACKIRI notation can be dealt with declaring '<' and '>' as
>    quote chars, but this precludes them from being used as operators or
>    punctuation.
>
> 4) UNITERM's are defined to be either positional or attributed, but not
>    both:
>
>        UNITERM ::= Const '(' (TERM* | (Name '->' TERM)*) ')'
>
>    This creates an inherently unliftable reduce/reduce syntactic ambiguity:
>
>        =============================
>        STATE NUMBER: 54
>        =============================
>        This state has conflicts:
>
>        Unresolved R/R conflict: choosing R82    over R84,     on input 
'IDENTIFIER'
>        Unresolved R/R conflict: choosing R82    over R84,     on input 'CLOSEPAR'
>        -----------------------------
>        [45] UniTerm --> Const 'OPENPAR' . UniTermBody 'CLOSEPAR'
>            Preceding states: {22, 51, 95, 120, 127, 148}
>            Follow set: {'CLOSEPAR'}
>        [66] UniTermBody --> . Term_star
>            Preceding states: {54}
>        [67] UniTermBody --> . TermAttribute_star
>            Preceding states: {54}
>        [82] Term_star --> .
>            Preceding states: {54}
>            Lookahead set: {'EXTERNAL', 'NUMBER', 'LOCALNAME', 'VARIABLE', 
'STRING', 'IDENTIFIER', 'ANGLEBRACKIRI', 'CLOSEPAR', 'OPENMETA', 'COLON'}
>        [83] Term_star --> . Term_star Term
>            Preceding states: {54}
>        [84] TermAttribute_star --> .
>            Preceding states: {54}
>            Lookahead set: {'IDENTIFIER', 'CLOSEPAR'}
>        [85] TermAttribute_star --> . TermAttribute_star TermAttribute
>            Preceding states: {54}
>        -----------------------------
>        With UniTermBody, go to state 55
>        With Term_star, go to state 56
>        With TermAttribute_star, go to state 57
>
>     A possible workaround is to use modify the rule to:
>
>        UNITERM ::= Const '(' (TERM | (Name '->' TERM))* ')'
>
>     (i.e., accepting mixed positional and attributed term bodies), and
>     perform a check ex post facto.
>
> 5) According to http://www.w3.org/TR/rif-bld/#sec-ebnf-condition-language:
>
>       An IRICONST is the special case of a Const with the symbol
>       space rif:iri, again permitting the shortcut forms defined in
>       http://www.w3.org/TR/rif-bld/#ref-rif-dtb. One such specialization
>       is '"' IRI '"^^' 'rif:iri' from the Const production, where IRI is a
>       sequence of Unicode characters that forms an internationalized
>       resource identifier as defined by 
http://www.w3.org/TR/rif-bld/#ref-rfc-3987.
>
>     However, this definition complicates tokenizing as it becomes
>     impossible to distinguish the special case from the general one.
>
>     A possible workaround is to see an IRICONST as just a fully qualified
>     constant; i.e., accepting even not "rif:iri" symbol spaces and
>     performing the check ex post fact.
>
> Again, this is not an exhaustive list of issues. Be those as they may, I
> will continue working on trying to produce a working [A]PS parser as my
> time permits while on the road (I have been traveling and will be until
> Nov. 11).
>
> It will be good that the PS Task Force discuss and find resolutions to all
> such issues.
>
> Regards,
>
> -hak
> --
> Hassan At-Kaci  *  ILOG, Inc. - Product Division R&D
> http://koala.ilog.fr/wiki/bin/view/Main/HassanAitKaci
>
>
-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty
Received on Friday, 21 November 2008 15:32:30 GMT

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