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@ref vs @nodeset

From: Ulrich Nicolas Lissé <unl@dreamlab.net>
Date: Wed, 17 Mar 2010 08:34:44 +0100
Message-ID: <4BA08614.3000808@dreamlab.net>
To: Forms WG <public-forms@w3.org>
Dear Group,

I followed the previous discussions with great attention. Since I can't
attend neither today's telecon nor the F2F I'll try to condense my
opinion here.

I'm definitely a supporter of unifying @ref and @nodeset. It would
obviously make author's life easier. And I think it would make also
implementor's life easier. Here's why:

The distinction between single-node and nodeset bindings is a no-brainer
and should be handled by the control (as Erik pointed out in [1]). We
already have language in the Spec that says which binding capabilities a
control has (e.g. "Data Binding Restrictions: Binds to any
simpleContent..." for xf:input). It would be just consistent to expand
that language to include the first-node rule for single-node bindings.

Furthermore, I don't see any need to invent a new attribute specifying
the binding type. First, I'm strongly opposed to introduce new
attributes, because XForms is already complex enough and just adding
another one would make things even worse. Second, I think it would be
actually wrong to add an attribute specifying binding behaviour, because
it would appear to authors like they could change it's value. Binding
behaviour of a control is given by our Spec, not on the markup level.

In [2] Charlie raised a concern about extensions like <xhtml:p
@ref="..."/> leading to the interesting question of who is in charge of
the binding: the model or the control? I think it should be the control.
And I don't see so much problems with that approach, since it reminds me
on the Dependency Injection [3] programming style. Instead of requiring
the model to actively manage all dependent bindings and their
update/event cycles, the control registers with the model and says: Hey,
I'm a single-node binding control - please provide me with updates for
that certain binding. That would work particularly well for extension
elements.

IMHO we overloaded @ref/@nodeset semantics in the past. They specify at
least two orthogonal concepts: The binding type of control and a
communication channel for events. As we are approaching an overhaul of
UI events, we should sort that out.

I would like to propose to deprecate @nodeset in XForms 1.2, so that
either @ref or @nodeset can be used where @nodeset is required in XForms
1.1. That won't break any existing form. In XForms 2.0 we could drop
@nodeset, and even switch to @select if we want to.

Regards,
Uli.

[1] http://lists.w3.org/Archives/Public/public-forms/2010Mar/0003.html
[2]
http://lists.w3.org/Archives/Public/public-forms/2010Mar/att-0009/2010-03-10.html
[3] http://martinfowler.com/articles/injection.html
-- 
Ulrich Nicolas Lissé
Received on Wednesday, 17 March 2010 07:35:20 UTC

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