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Re: declarative expressons in WF2

From: Dave Raggett <dsr@w3.org>
Date: Sun, 25 Mar 2007 20:16:21 +0100 (BST)
To: Anne van Kesteren <annevk@opera.com>
cc: Ian Hickson <ian@hixie.ch>, Sebastian Schnitzenbaumer <sebastian@dreamlab.net>, public-html@w3.org
Message-ID: <Pine.LNX.4.64.0703251940500.13072@localhost>

On Sun, 25 Mar 2007, Anne van Kesteren wrote:

> On Sun, 25 Mar 2007 20:17:54 +0200, Dave Raggett <dsr@w3.org> wrote:
>> I have introduced a grammar for a subset of ECMA 262 r-value 
>> expressions together with additional constraints that ensure that 
>> the expressions can be statically analysed. See:
>>
>>   http://www.w3.org/2007/03/XForms-Transitional/#expr-syntax
>
>  Note that functions must be side-effect free and avoid
>  introducing dependencies on form fields other than those
>  passed via the function's arguments. This is needed to
>  ensure that the expression can be statically analysed.
>
> Doesn't help an implementor much. It seems you still haven't 
> addressed the original concern various people expressed either on 
> this mailing list or #html-wg.

How so?

We all know that it is impractical to analyse turing complete 
code, and browsers wisely don't try to do so. If your scripts don't 
behave as you expect, it is generally up to you as the programmer to 
sort it out.

For the simplest case authors wouldn't need to write functions so 
that problem wouldn't arise. Any functions that the editor provides 
would have been written by experts and subject to testing to ensure
that these functions abide by the rules.

You might say "What's wrong with event handlers?. Everyone in the 
HTML WG is very comfortable with writing scripts for event handlers, 
so what's the problem?"

Well we have a duty of care to the rest of the population who don't 
know and don't care about scripting. If we ignore that duty then the 
market will make a correction. HTML will be sidelined as a delivery 
format and won't be an editing format.

In IRC you suggested that editors could recognize the scripts that 
they generated. That's true, but leads to the undesirable situation 
where you can only edit a document if it was created by that editor.
Switching back to a text editor isn't an option for people who don't 
know about HTML, CSS or JavaScript.

The same problem occurs if the editor saves the semantics for the 
event handlers in a non-standard declarative format since this will 
prevent other editors who don't know about that format from being 
able to offer an effective service to non-technical users.

I think this is a critical question for the HTML working group. I am 
striving to provide a technically sound solution for extending WF2 
with declarative expressions, but if the working group isn't willing 
to consider this, I would like a decision earlier rather than later.

  Dave Raggett <dsr@w3.org> http://www.w3.org/People/Raggett
Received on Sunday, 25 March 2007 19:16:51 GMT

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