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Re: Question about lazy authoring

From: John Boyer <boyerj@ca.ibm.com>
Date: Mon, 16 Feb 2009 22:56:30 -0800
To: Erik Bruchez <ebruchez@orbeon.com>, Nick_Van_den_Bleeken@inventivegroup.com
Cc: Forms WG <public-forms@w3.org>
Message-ID: <OF82D28BAB.49BC09DF-ON88257560.0024F7F0-88257560.002612C1@ca.ibm.com>
Hi Nick, 

Why is this a question about lazy authoring?
The test you identified is testing the IDREF mechanism.  It is not 
intended to test of lazy authoring, so it is a bad test because it will 
run afoul of a lazy authoring problem before getting to the issue it 
claims to test, which is whether the index function returns NaN when it 
can't find the identified repeat.

Erik's point about amending the eval context of an xpath when their is no 
context node would make a good feature/suggestion+test for Section 7.2, 
except it is probably better for XForms 2.0 because in XForms 1.x we have 
Xpath 1.0, which requires a context node as part of the context.  I 
suppose we could make do if all current xpath 1.0 implementations allowed 
evaluation without a starting context node, but this is probably not an 
issue we have to spend a lot of cycles on right now.

For lazy authoring, I think you need at least one real UI binding to be 
expressed because otherwise the lazy authored instance will be empty, 
which is not allowed.  If you squint at the spec in just the right way, 
you can see it producing the same kind of exception as if you had put this 
into the model:


John M. Boyer, Ph.D.
STSM, Interactive Documents and Web 2.0 Applications
Chair, W3C Forms Working Group
Workplace, Portal and Collaboration Software
IBM Victoria Software Lab
E-Mail: boyerj@ca.ibm.com 

Blog: http://www.ibm.com/developerworks/blogs/page/JohnBoyer
Blog RSS feed: 

Erik Bruchez <ebruchez@orbeon.com>
Forms WG <public-forms@w3.org>
02/16/2009 01:08 PM
Re: Question about lazy authoring

XProc solves this issue by saying the following [1]:

   "If there is no binding and there is no default readable port then 
the context node is an empty document node."

Something like this would make sense to me for XForms, but it would 
have to be added to the spec.


[1] http://www.w3.org/TR/xproc/#xpath10-processors

On Feb 16, 2009, at 1:32 AM, Nick Van den Bleeken wrote:

> All,
> Test case 4.7.c has no instance and no controls that have a node set 
> binding, but it has a value attribute on an output control is this 
> supposed to work?
> In my opinion you can't construct an XPath context because you don't 
> have an instance, because no form controls refer to an instance... I 
> can work around this and create an instance when there is a form 
> control that has a value attribute, but this isn't correct to how I 
> read the spec.
> What are your opinions about this?
> Regards,
> Nick Van den Bleeken
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Received on Tuesday, 17 February 2009 06:56:30 UTC

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