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Re: Implementors please read: poll about select1 and empty values

From: John Boyer <boyerj@ca.ibm.com>
Date: Thu, 9 Dec 2010 08:40:28 -0800
To: "Leigh L. Klotz, Jr." <Leigh.Klotz@Xerox.com>
Cc: public-forms@w3.org, www-forms@w3.org
Message-ID: <OFA9350E55.4EDFDC9A-ON882577F4.005AB9CF-882577F4.005B9A9F@ca.ibm.com>
Modulo my comments about why the spec might have originally contained that 
language (consistency, required MIP), this topic rings a bell as having 
been discussed and decided, perhaps a couple of years back, and that 
perhaps the human error of not creating an action item to fix the spec may 
have caused us to... not fix the spec.

The bell I seem to recall is that we wanted the possibility of getting a 
select1 back into the "unselected" state.  One can already do this for a 
select by simply unselecting everything, but for a select1 the only way to 
do it is to have an item with an empty value.  I seem to recall our 
concluding that a form author who doesn't like that feature in his forms 
has options for simply not using that feature.  Further, if the select1 is 
bound to a required node, it is of no consequence that the user's choice 
puts the form back into an unsubmittable state.  If that is undesirable, 
then it is because the form incorrectly designates the node as required.

As for answering the implementers poll, the IBM Forms product implements 
the ability of a select1 control to choose an item whose value is empty. 
The emptiness is transmitted to the data node to which the select1 is 
bound.  If that data node is required, then the form control reverts to a 
display state that indicates the user must make a choice.

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: 

"Leigh L. Klotz, Jr." <Leigh.Klotz@Xerox.com>
12/08/2010 10:17 AM
Implementors please read: poll about select1 and empty values

A question has come up about conformance and interoperability of XForms 
processors with regard to the behavior of select1 when a value is the 
empty string or whitespace only. 

This message is a poll to find out how select1 with an empty item/value 
element behaves in existing XForms 1.1 implementations.  Based on the 
results of this poll we may add additional test cases, additional 
clarification, issue an erratum, or propose new features for XForms 1.2.  

The XForms 1.1 Recommendation says [1] about select1 (and select as well):
"For both closed and open selections, any selection item with a storage 
value which is empty or which contains only white space characters must 
remain deselected."

Nick van den Bleeken tentatively reported that least one implementation 
supports a select1/item/label for the empty item/value.

John Boyer and I both noted that select has this implementation 
requirement because its space-separated values in list content are 
indistinguishable from empty.  In short, the absence of any selected item 
is ithe indication that no item is selected.

John further noted, however, that the requirement on select1 is motivated 
not only by consistency with select, but also by another point, that the 
"required" MIP be used to indicate that a value has been set.  John noted 
that xsi:nil can also be used for this purpose, but is not well understood 
or implemented. 

John suggested to form designers that a "none" value for any select1 
control-bound data would better be represented by a distinguished value 
chosen by the application, e.g. "none" or "n", rather than an empty value.

I noted that only if the XForms application and the data are co-designed 
can the form designer can satisfy this requirement, and that web resources 
may require an empty string to indicate a value of "none," and that 
allowing a binding of a label gives form designers the ability to express 
this UI.

As a result of this discussion, we are polling implementations and seeking 
feedback on the presentation and behavior of empty ref node values and 
empty item/value (and by extension, itemset) in select1.

Test Case:

I have produced a test and made it work using xsltforms. 
It is available at http://xformstest.org/2010/12/select1-empty and please 
choose select1-empty.xml
We're asking implementors to adapt and run this test case and report 
A sample report is below:

Test Case Results Example
For the sample I produced, here are the results for the select1 cases with 
an empty item/value.
(The test page also includes controls with no empty item/value).

no appearance:
displays as pulldown menu
empty value displays as a blank item inside select1. (to spec)
selecting the "(empty)" labeled item causes only that control to change. 
(partially to spec)
after that, selecting the unlabeled item causes all form controls bound to 
the node to change to the "(empty)" labeled item (not to spec)
selecting the "full" labeled item causes all controls to change to "full". 
(to spec)
selecting the "full" labeled item causes the blank item to disappear from 
all select1 controls, however the explicit "(empty)" choice remains. 
selecting the "(enpty)" labeled item again causes the blank item to 
re-appear in all select1 controls (???)

displays as pulldown menu
same behavior as above

displays as in-place visible menus with one selection allowed
same behavior as above

displays as radio buttons; no blank or unlabeled radio button
empty value displays as a selected "(empty)" radio button. (NOT to spec)
selecting the "(empty)" labeled item causes all form controls to change to 
display the unlabeled item. (to spec)
selecting the "full" labeled item causes all controls to change to "full". 
(to spec)
selecting the "full" labeled item causes the blank item to disappear from 
all select1 controls, however the explicit "(empty)" choice remains;
selecting the "(empty)" labeled item again causes the blank item to 
re-appear in all select1 controls. (???)

Of the above, only the full appearance (radio) had a notable behavior: it 
offered no way to choose the empty item, and if the empty item were chosen 
by another control, it displayed with no selection.


[1] http://www.w3.org/TR/xforms11/#ui-selectOne 
Received on Thursday, 9 December 2010 16:41:06 UTC

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