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Re: Nested binds in future versions of XForms spec

From: John Boyer <boyerj@ca.ibm.com>
Date: Mon, 29 Nov 2010 09:29:58 -0800
To: Kurt Cagle <kurt.cagle@gmail.com>
Cc: Claudius Teodorescu <claud108@yahoo.com>, www-forms@w3.org
Message-ID: <OF3F35157B.C719627B-ON882577EA.005E9125-882577EA.006022FE@ca.ibm.com>
Hi guys,

Nested binds have been supported in the spec for a very very long time 
now.
I actually don't recall a time that they were *not* supported, but I do 
recall several discussions in the fives-yeasr-ago timeframe because 
1) implementers were doing it slightly differently, causing subtle 
differences in the behavior of xpath functions like position()
2) we needed to do some work to define what it meant to make an IDREF to 
an inner bind whose containing bind's nodeset had size > 1

These were also worked out a long time ago and support appears in XForms 
1.0 third edition and XForms 1.1.

I believe Claudius is actually asking when implementers will fully support 
the "Context Everywhere" feature.  For XForms 1.1, the context attribute 
is only supported on the insert and delete elements.  Although we really 
wanted the context attribute in other places, we really had to stop adding 
things to 1.1, so it was deferred to 1.2.

One of the places where the context attribute would be useful is on inner 
nested binds, provided the meaning is that it sets the context for 
evaluating the xpaths but does not change the node to which any MIP 
expressions apply.  This makes sense on a number of levels, including
1) context should not have special side effects on a particular element 
like bind; it should just set the eval context for expressions on the 
element
2) there would be equivalence with alternate markup formats that would 
make better sense, e.g <bind nodeset="x"> <calculate context=".." 
value="a+b"/> </bind>

Anyway, I've now created the proper link from the "context everywhere" 
feature here:
http://www.w3.org/MarkUp/Forms/wiki/@context_everywhere

to the other page about unified eval context that Claudius was reading, 
because they are about the same thing and because the "context everywhere" 
feature has the status "Accepted" working group status for XForms 1.2 and 
has an editor assigned (your truly, in fact).

So, yes, it's coming in the spec sense, and I also believe it is an *easy* 
one for implementers to get going, so lean on your favorite implementer a 
bit if you need this sooner rather than later because the implementations 
lead the spec.

Best regards,
John M. Boyer, Ph.D.
Distinguished Engineer, IBM Forms and Smarter Web Applications
IBM Canada Software Lab, Victoria
E-Mail: boyerj@ca.ibm.com 

Blog: http://www.ibm.com/developerworks/blogs/page/JohnBoyer
Blog RSS feed: 
http://www.ibm.com/developerworks/blogs/rss/JohnBoyer?flavor=rssdw





From:
Kurt Cagle <kurt.cagle@gmail.com>
To:
Claudius Teodorescu <claud108@yahoo.com>
Cc:
www-forms@w3.org
Date:
11/29/2010 07:07 AM
Subject:
Re: Nested binds in future versions of XForms spec



Claudius,
Speaking for myself, I know that most of the curent XForms implementation 
are offering nested binds as extensions, and there are enough advantages 
to them that I wouldbe very surprised if they did not appear in the 1.2 
specification. 
There are similarly discussions about defining contextual variables in 
1.2, though at this point the working group is really just getting up to 
speed after the chartering earlier this year. I know that both have been 
discussed on the futures lists.
Kurt Cagle
On Nov 29, 2010 9:48 AM, "Claudius Teodorescu" <claud108@yahoo.com> wrote:
> Hi,
> 
> I would like to ask if anybody can say something about nested binds in 
future
> versions of XForms spec. Will nested binds exist or not?
> 
> I am asking this in the context of these nice refinements of bind 
element:
> http://www.w3.org/MarkUp/Forms/wiki/Unified_evaluation_context
> 
> 
> Thank you,
> Claudius Teodorescu
> 
> 
> 
Received on Monday, 29 November 2010 17:30:34 GMT

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