Re: [Xsltforms-support] Binding to optional element

[COUTHURES A. <ala...@ag...>]

Hey Micah,
> This was difficult to do in XForms 1.0. What's the latest state of the art?
>
> Say I have an XML instance like this:
> <root>
>    <format>xml</format>
> </root>
>
> Possible values for the format element are "xml", "text", "binary", or a default setting, indicated by a complete absence of the <format> element. I'd like this to attach to a select1 with four choices:
>
> <xf:select1 ref="format">...
>
> * xml
> * text
> * binary
> * default
>
> Where the first three set the value of the <format> element, and the fourth omits the element altogether. In XForms 1.0, the difficulty comes from binding to a nonexistent element. Are there features from 1.1, 1.2, or XSLTForms that make this case easier? Anyone have an example?
This is clearly a real world situation: the lack of an XML element has 
its own meaning in the XML world.

The problem with XForms 1.1 is that an instance has two purposes: to act 
as a sort of schema and to represent the initial values.

Being a sort of elementary schema, every element has to be present, even 
without a value. Lacks of element will disable corresponding bindings. 
Within a repeat, it's not possible to delete the very last item and then 
insert it again because there is no node to copy anymore...

I think this should be in XForms 2.0 to separate this without confusion: 
one schema and one instance with initial values.

XSLTForms doesn't support it yet but it's a very interesting feature 
because of this current restriction.

Using an extra work instance in XForms 1.1 is, usually, a possible 
workaround, with some actions (depending on @if probably) to synchronize 
instances. Sorry, I haven't develop one yet myself for this kind of 
situation.

-Alain