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Message-ID: <42A45D83.9010508@reverycodes.com>
Date: Mon, 06 Jun 2005 10:28:19 -0400
From: Vadim Gritsenko <vadim@reverycodes.com>
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To: dev@cocoon.apache.org
Subject: Re: [RFE] Some enhancements to XSP
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Nathaniel Alfred wrote:
>>From: Vadim Gritsenko [mailto:vadim@reverycodes.com]
> 
>>>Instead of "?" one could also use another character provided it is sufficiently
>>>unlikely that the sequence curly-char appears in XSP-embedded content or where 
>>>XSP can be embedded (XSL).  The special character should not be valid at the
>>>beginning of an expression at least for CSS, HTML, Java, Javascript, Perl, 
>>>and XSLT.  That excludes
>>>
>>>    + " * % & ` @ ' ^ ~ ! [ $ - . ( /
>>>
>>>but leaves as sensible alternatives
>>>
>>>    {#expr}
>>>    {=expr}
>>>    {:expr}
>>>    {?expr}
>>>
>>>Whatever special character we agree on, it should be always the same in all
>>>contexts and always enabled.
>>>
>>>Any preferrences which character to use?
>>
>>Yes. Given that (a) XSLT already has '{foo}' syntax, and uses '{{foo}}' for 
>>escaping; and given that the only other XSP implementation (AxKit) uses same 
>>syntax as in XSLT, I'm for using that same syntax too.
> 
> 
> I think it is a bad idea to use exactly the same syntax as for XSLT because it
> makes really awkward to use XSP attribute interpolation inside logicsheets.

You haven't written any XSLT producing Ant files recently, have you? :-)
Now it seems really easy to me, you simply write:

   <img src="{{foo}}"/>

in the XSLT.


> You end up wasting your time figuring out which curly mountain is needed to
> get the expression to be interpreted by the right engine.
> 
> It should be easy for both humans and the XSP processor to distinguish between
> XSP and XSLT expressions.

I don't get your point about XSP processor. It is already dead easy for it.


> I don't know AxKit in detail but I assume that them using "{foo}" syntax means
> that they are not using XSLT-based logicsheets.

It's implemented in PERL, for logicsheets they have .pm files, iirc.


> Anyway, we can still claim to
> use a common standard by defining:
> 
>    interpolated-expr ::= '{' language-expr '}'
>    language-expr ::= perl-expr | '?' java-expr | '?' javascript-expr | '?' python-expr 

Extra character does not add any elegance, imho.


>>As for backward compatibility, is is already solved by:
>>
>>   <xsp:page attribute-value-interpolation="no">
> 
> 
> But the default value should be attribute-value-interpolation="yes", provided
> we can agree on a syntax which is highly unlikely to be used in existing XSPs.

If default is "yes" by default :-) then you'll break all the installations of 
Cocoon out there in one shot. *Not* nice!

Hence, default must be at least configurable - in the cocoon.xconf.

Vadim