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RE: Insert / delete confusion

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Fri, 1 Jul 2005 13:33:27 +0100
Message-ID: <2F376A04-B8DE-4CC7-86A7-5BF6A7FA68A4@S009>
To: "'Erik Bruchez'" <erik@bruchez.org>, <www-forms@w3.org>

Hi Erik,

> This is probably (hopefully) covered in the upcoming edition 
> of 1.0, but here it goes anyway:
> 
> XForms 1.0 was initially very clear that the insert action 
> copies a prototype from the initial instance data. The errata 
> then (and also very
> clearly) changed this behavior.

The story of xf:insert actually goes back one step further! Initially -- in
early drafts -- the behaviour was to duplicate the last node in a nodeset.
The problem with this is that you can't then insert a node into an empty
nodeset, so in an attempt to solve this, the spec was changed to say that
you should duplicate the last node in the _initial instance data_. But that
too has its own problems, which is that you can't find that initial instance
data if you are about to insert into an nodeset .

Whichever way you twist and turn, xf:insert has problems because everything
is worked out based on a nodeset, not on a parent node. So, the decision was
taken to revert xf:insert back to the first version -- duplicate the last
node in the list -- and then add xf:duplicate to give us the ability to
insert nodes into empty node lists (by being able to append a node to
another).


> The current public XForms 1.1 
> draft however restates that 1.0 uses a prototype from the 
> initial instance data, the some additions: in 1.1 draft, the 
> prototype is copied from the position specified by the "at" 
> attribute.

I can't see that. In:

  <http://www.w3.org/TR/xforms11/#insertAndDelete-action>

it says that it doesn't use the initialisation instance data, and instead
uses the live DOM.

> Also, trying to delete the last node of a collection has no effect.

That's new, I agree...and I have to say I've never noticed that before! You
are right that it makes 1.0 and 1.1 forms behave slightly differently.


> Given these contradictions, what is an implementor of 1.0 to 
> do?

As far as I can see the only 'contradiction' is this point about xf:delete.
Since 1.1 is still only a draft, I would go with the 1.0 functionality,
although obviously including any points from the errata.


> Do current XForms engines actually implement insert by 
> copying a node from the initial instance data, or do they 
> implement what's in the erroneous errata (tm)? Does it make 
> sense to already implement the proposed 1.1 behavior?

I think most now use the live instance data for the prototypical instance.

Regards,

Mark


Mark Birbeck
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Received on Friday, 1 July 2005 12:33:55 GMT

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