On Fri, Oct 11, 2002 at 04:41:41AM -0400, Eric S. Raymond wrote:
> Daniel Veillard <[EMAIL PROTECTED]>:
> > Now to be relatively specific about <?if?> as much as I can since I
> > don't have any clear picture of how the selection is actually done, it seems
> > to be in the line of the previously found standard extention abuses
> > like #pragma foobar for Winblows C compilers or various custom PI
> > that each SGML toolchains seems to have developped to tie in their
> > customers in the 90's (I may get some heat for this, I don't care ;-)
>
> You know, there's reason people keep re-inventing mechanisms for this.
> It's because they need to get work done -- and getting work done often
> means wanting to conditionalize documents without spending days on some
> elaborate custom XSLT hack.
But then you put the burden on someone else. And an underspecified,
underreviewed mechanism is the hell of the maintainer's
> > they really need, that there is a clean and public description with
> > review of the suggested extension, then I would certainly be an early
> > implementor of said feature.
>
> Attribute/value pairs from the command line are matched
> against the attributes associated with certain processing
> instructions in the document. The instructions are <?if?> and
> its inverse <?if not?>, <?elif?> and its inverse <?elif not?>,
> <?else?>, and <?fi?>.
>
> Argument/value pairs given on the command line are checked
> against the value of corresponding attributes in the
> conditional processing instructions. An `attribute match'
> happens if an attribute occurs in both the command-line
> arguments and the tag, and the values match. An `attribute
> mismatch' happens if an attribute occurs in both the
> command-line arguments and the tag, but the values do not
> match.
>
> Spans between <?if?> or <?elif?> and the next conditional
> processing instruction at the same nesting level are passed
> through unaltered if there is at least one attribute match and
> no attribute mismatch; spans between <?if not?> and <?elif
> not?> and the next conditional processing instruction are
> passed otherwise. Spans between <?else?> and the next
> conditional-processing tag are passed through only if no
> previous span at the same level has been passed through.
> <?if?> and <?fi?> (and their `not' variants) change the
> current nesting level; <?else?> and <?elif?> do not.
>
> All these processing instructions will be removed from the
> output produced. Aside from the conditionalization, all other
> input is passed through untouched; in particular, entity
> references are not resolved.
>
> Value matching is by string equality, except that "|" in an
> attribute value is interpreted as an alternation character.
> Thus, saying foo='red|blue' on the command line enables
> conditions red and blue. Saying color='black|white' in a tag
> matches command-line conditions color='black' and
> color='white'.
>
> Here is an example:
> Always issue this text.
> <?if condition='html'?>
> Issue this text if 'condition=html' is given on the command line.
> <?elif condition='pdf|ps'?>
> Issue this text if 'condition=pdf' or 'condition=ps'
> is given on the command line.
> <?else?>
> Otherwise issue this text.
> <?fi?>
> Always issue this text.
Doesn't cover a hell of issues, 2mn read just pops up tons of unspecified
behaviour or serious problems. Heck, even the "condition=" syntax is only
given in the example ....
- well formedness breakage, your description is done at the
serialization level, it has 0 garantee on the level of XML well-formedness
<?if condition='html'?>
<foo>
<?elif condition='pdf|ps'?>
</foo>
<?fi?>
What gives ??? A further XML well formedness error ? In that case it's
better left external. Otherwise you'd have to start to give a description
in terms of the infoset, or similar like XInclude does.
- malformed preprocessor commands
<?if?>
<?elif cond='pdf
|foo'?>
unlatched <?else?> or <?fi?>, etc, etc ...
what is handled, and how ?
Daniel
--
Daniel Veillard | Red Hat Network https://rhn.redhat.com/
[EMAIL PROTECTED] | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
