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Re: [XForms 1.1] Questioning the iteration of certain actions (section 10.15)

From: Ulrich Nicolas Lissé <unlisse@googlemail.com>
Date: Tue, 4 Dec 2007 00:50:30 +0100
Message-ID: <da289f40712031550mda3289bp152b3e974bfa915b@mail.gmail.com>
To: "Clark, John" <CLARKJ2@ccf.org>
Cc: www-forms-editor@w3.org, www-forms@w3.org
Hi John,

we discussed this issue during the last WG telecon. I'm sorry that my
first reply was a bit sparse. Here are some more elaborated reasons
why @while is allowed on any action element:

1. Some actions seem to be side-effect free, but they are not because
they generate additional events. For example xf:setfocus may lead to a
DOMFocusIn event on the target control. There may be arbitrary actions
attached as event handlers for DOMFocusIn on that control which get
executed in turn.

2. There is not much sense in disallowing @while on certain actions
because of the xf:action wrapper element. So even if @while would not
be allowed on certain actions, you could easily wrap an xf:action with
@while around these.

3. The WG is striving to define XForms in a more modular way in
future. Actions could then come from separate specifications, so you
might have @while on a SMIL action.

Hope this helps,

On Nov 12, 2007 8:59 PM, Clark, John <CLARKJ2@ccf.org> wrote:
> To Whom It May Concern:
>  The XForms 1.1 Actions Module[0] supports iterated actions using the
> `while` attribute.  This attribute is allowed on any action element, but it
> seems that it is only useful on a subset of the possible action elements.
> The `xf:message`[1] action "encapsulates a message to be displayed to the
> user"; it does not change the model, and so the `while` expression will
> remain true after each display of the message, causing an infinite loop.  It
> also might not make sense to allow the `while` attribute on the
> `xf:setfocus`, `xf:load`, `xf:rebuild`, `xf:recalculate`, `xf:refresh`, or
> `xf:revalidate` actions for essentially the same reason as in the case of
> `xf:message`, but I am less sure of those cases.
>  Should the specification disallow the use of the `while` attribute in these
> problematic cases?  If not, in what way is iteration useful in these cases?
>  Thank you for your consideration.
>  Sincerely,
>      John L. Clark
>  [0] http://www.w3.org/TR/xforms11/#action
>  [1] http://www.w3.org/TR/xforms11/#action-message
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Ulrich Nicolas Lissé
Received on Monday, 3 December 2007 23:50:41 UTC

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