Re: Make its:param optional?

Hi Jirka, Yves, all,

OK, so we keep its:param I guess. Would it be OK to add the following note
to the its:param section:

its:param adds flexibility in real-life situations. However in general it
is recommended not to use its:param. It is disallowed in CSS, see section
5.3.5, since the current version of CSS does not allow variable bindings.
XPath APIs for processing global rules sometimes do not have a standard way
of binding variables to an XPath evaluation. In summary, not using
its:param will foster the re-use of global rules across implementations.


I know we could do that in a BP document, but summarize the point of the
discussion now might help.


Felix

2012/10/11 Jirka Kosek <jirka@kosek.cz>

> On 11.10.2012 16:30, Felix Sasaki wrote:
> > ok ... but what to do about CSS  selectors? How does its:param interact
> > with these? We just end up with a lot of combinations of ITS processors:
>
> its:param is disallowed for CSS, see section 5.3.5:
>
> "Implementation MUST support the param element for all query languages
> it supports and which at the same time define how variables are bind for
> evaluation of selector expression."
>
> CSS doesn't define variable binding (at least current version of CSS,
> there is some new work on adding variables into CSS), so its:param has
> no effect on CSS selectors when queryLanguage="css"
>
> > implements global rules and XPath 1.0
> > implements global rules with XPath 1.0 and param
> > implements global rules and XPath 2.0
> > implements global rules with XPath 2.0 and param
> > implements global rules using CSS
> > implements global rules using CSS and param
> >
> > I'm not so much worried about the implementation choices - a well
> > documented implementation will make the choice clear -, but rather about
> > re-usage of rules across implementations. With ITS 1.0, each rule could
> > easily be re-used, because there is just one conformance class: global
> > rules. With the above, in fact we have six classes.
>
> As XPath 1.0 is default query language I think that it will be
> prevailing QL, and that reasonable ITS users will not use something
> different. While its:param can be useful, it addresses very specific
> needs so it will not be extensively used IMHO. So in practice I think
> that we will have similar interop as with ITS 1.0.
>
> > Also, how to tell rule authors what of the choice the best practice is?
> Or
> > in summary, the flexibility creates drawbacks on the rule re-usage and
> best
> > practices side ...
>
> The best practice is XPath 1.0 without params. We might issue updated
> I18NBP document once ITS 2.0 is REC.
>
>                                 Jirka
>
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>   Jirka Kosek      e-mail: jirka@kosek.cz      http://xmlguru.cz
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-- 
Felix Sasaki
DFKI / W3C Fellow