unplanned deviation from SPARQL grammar in Turtle and Trig

I blindly replied to Guus's agenda with an issue I noticed in the
grammar. Andy and David requested that I move it to it's own thread
so I'm including the earlier conversation here. The tail of the old
thread is <http://www.w3.org/mid/3025C528-82B8-47A4-9C83-34FAB4B76F45@3roundstones.com>. The summary is 12 lines down from here.


* David Wood <david@3roundstones.com> [2014-02-12 08:16-0500]
> On Feb 12, 2014, at 07:20, Guus Schreiber <guus.schreiber@vu.nl> wrote:
> 
> > 
> > 
> > On 12-02-14 13:01, Sandro Hawke wrote:
> >> On February 12, 2014 6:10:20 AM EST, Eric Prud'hommeaux <eric@w3.org>
> >> wrote:
...
> >>> More interestingly, I noticed that we deviated from SPARQL's
> >>> definition of strings 20 months ago when a re-gen of the HTML
> >>> grammar stripped some ()s, going from:
> >>> 
> >>> [157s] STRING_LITERAL_LONG1 ::= "'''" (("'" | "''")? ([^'\] | ECHAR
> >>> | UCHAR))* "'''" [158s] STRING_LITERAL_LONG2 ::= '"""' (('"' |
> >>> '""')? ([^"\] | ECHAR | UCHAR))* '"""' to: [25]
> >>> STRING_LITERAL_LONG1 ::= "'''" (("'" | "''")?  [^'\] | ECHAR |
> >>> UCHAR) * "'''" [26]   STRING_LITERAL_LONG2 ::= '"""' (('"' | '""')?
> >>> [^"\] | ECHAR | UCHAR) * '"""' —
> >>> <https://dvcs.w3.org/hg/rdf/raw-file/b40e79fe8bbc/rdf-turtle/turtle-bnf.html>
> >>> 
> >>> 
> >>> 
> > In the former language, <s> <p> """ "\u0061 """ . is legal and in the
> >>> latter, an embedded quote must not be followed by ECHAR (e.g. \")
> >>> or UCHAR (e.g. \u0061). Unfortunately, this change was pre-Trig so
> >>> the issue exists there as well.
> >>> 
> >>> I looked for tests with long (triple-quoted) strings with one or
> >>> two quotes followed by a backslash. We have none, but SPARQL does:
> >>> data-r2/syntax-sparql1/syntax-lit-17.rq:3:SELECT * WHERE { :x :p
> >>> '''Long''\\Literal with '\\ single quotes ''' }
> >>> data-r2/syntax-sparql1/syntax-lit-20.rq:3:SELECT * WHERE { :x :p
> >>> """Long""\\Literal with "\\ single quotes""" }
> >>> 
> >>> The closest we have is LITERAL_LONG2_with_1_squote.ttl:
> >>> <http://a.example/s> <http://a.example/p> """x""y""" . but the
> >>> nested ""s can be parsed by taking the longer of alternatives of
> >>> ('"' | '""').
> >>> 
> >>> What to do:
> >>> 
> >>> I propose the bold step of restoring the SPARQL grammar, noting
> >>> that it doesn't change any of our test results.
> >>> 
> >> 
> >> Argh.   Either that or we put it in the errata now.
> > 
> > If it is really an error we should fix it now. Given our explicit goal, known to to user community, to align Turtle as much as possible with SPARQL, it makes sense to view this as an error.
> 
> 
> In the words of Eric Miller, "Eat crow when it is young and tender.”  I suggest to apologize, fix it and move on.  I view this as more procedural than world shattering. 
> 
> It would be a shame to have this in the errata before REC.
> 
> Regards,
> Dave
> --
> http://about.me/david_wood
> 
> 
> 
> > 
> > Gus
> > 
> >> 
> >> So this raises the ongoing-test-suite question.  We should add this
> >> (non-normatively, like the errata) to the test suite as well...  what
> >> exactly will be the process for that, post-REC?
> >> 
> >> - Sandro
> >> 
> >>> 
> >>>> Guus
> >>>> 
> >>>> [1] https://www.w3.org/2011/rdf-wg/wiki/Main_Page#REC_drafts
> 



-- 
-ericP

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Received on Wednesday, 12 February 2014 15:06:15 UTC