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Subject: [OASIS Issue Tracker] Commented: (OFFICE-2318) Public Comment: EBNF(ODF all versions) (CLONE)

    [ http://tools.oasis-open.org/issues/browse/OFFICE-2318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18848#action_18848 ] 

Dennis Hamilton commented on OFFICE-2318:

To be fair, there are some technical difficulties with the [XML 1.0] syntactic specification.  

1. There are decorators of the form [VC: ...] and [WFC: ... ] (described incorrectly in the syntax as using lower-case letters) and these are ambiguous with the structure for character selections where, e.g., [vc:.] represents any one of the characters "v", "c", ":", or ".".  Disambiguating this case is clumsy to describe using the EBNF itself.  What is is interesting from a computer-science perspective is that the restriction can't be expressed in BNF at all.  (Most EBNF "extensions" make it easier to express certain things but they don't express anything that can't be expressed in BNF.  The use of a generalized "-" grammar operation is a genuine extension and it can be quite sticky to automate although there are special cases that work just fine.)  This is probably not a real issue in practice and the specific case is not a problem.

2. The capitalizaiton of the names of syntactic forms is taken as significant with regard to regularity.   The claim is that capitalized names are "start symbols for regular languages."  That's a pretty technical distinction and it is not clear who is expected to verify that the capitalization is accurate.  This is particularly important because context can matter in whether or not what appears to be a regular language is regular in all of its occurrences in the particular grammar.  I can't tell from [XML 1.0] whether it is intended that the regular forms are taken to be greedy by definition (i.e., because they are capitalized) and the greediness figures in determining well-formedness.
   There is no harm and no foul in avoiding capitalization.  The syntactic definitions here for draw:formula and anim:formula do not capitalize although a significant number of the names are "start symbols for regular languages.".  I don't know if this has anything to do with the regularity convention as much as cultural practice, though.) 
   I find it undesirable to give so much technical significance to the simple capitalization of a term.  While it its of practical concern to know how much of a language's forms are regular, the determination of that characteristic should be left to technical procedures that are indifferent to how syntactic forms are named.  If it is desirable to have a way to assert that a production is greedy, some more-emphatic signal is needed.

3. The most-important "extension" in the EBNF of [XML 1.0] is the #xN character-code notation.  That doesn't do anything more complicated computer-science-wise as far as BNF is concerned.  It deals with a simple, serious practical problem that makes the [XML 1.0] approach worth its weight in gold.

> Public Comment: EBNF (ODF all versions) (CLONE)
> -----------------------------------------------
>                 Key: OFFICE-2318
>                 URL: http://tools.oasis-open.org/issues/browse/OFFICE-2318
>             Project: OASIS Open Document Format for Office Applications (OpenDocument) TC
>          Issue Type: Bug
>          Components: General
>    Affects Versions: ODF 1.2 Part 1 CD 4 
>            Reporter: Robert Weir 
>            Assignee: Patrick Durusau
>             Fix For: ODF 1.2 Part 1 CD 5
> Copied from office-comment list
> Original author: "Alex Brown" <alexb@griffinbrown.co.uk> 
> Original date: 22 Dec 2009 17:13:57 -0000
> Original URL: http://lists.oasis-open.org/archives/office-comment/200912/msg00017.html

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