Wrong XPath expression in Iterate example of XForms 1.1 CR

[Nick Van den Bleeken]

All,

Can it be that the 'if' XPath expression of the 3th setvalue in the 'Summing Selected Results'  sample [1] is missing an explicit reference to the default instance?

<trigger>
  <label>Get Sum</label>
  <action ev:event="DOMActivate">
     <setvalue ref="instance('temps')/counter" value="1"/>
     <setvalue ref="instance('temps')/accumulator" value="0"/>
     <action while="instance('temps')/counter <= count(/some/nodes)">
        <setvalue ref="instance('temps')/accumulator"
                  value=". + instance('default')/some/nodes[number(instance('temps')/counter)]"
                  if="boolean-from-string(/some/nodes[number(instance('temps')/counter)]/@selected)"/>
        <setvalue ref="instance('temps')/counter" value=". + 1"/>
     </action>
  </action>
</trigger>

The ref of the 3th setvalue changes the instance of the in-scope evaluation context to instance 'temps'.
But the '/some/nodes' are in the 'default' instance (see value of the setvalue).
-> we should change 'boolean-from-string(/some/nodes' to
     'boolean-from-string(instance('default')/some/nodes'


Regards,


Nick Van den Bleeken  -  Research & Development Manager
Inventive Designers
Phone: +32 - 3 - 8210170
Fax: +32 - 3 - 8210171
Email: Nick_Van_den_Bleeken@...

1: http://www.w3.org/TR/xforms11/#action-iterated

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[John Boyer]

Hi Nick,

The 'if' and 'while' attributes use the in-scope evaluation context before the action is executed, so they are not subject to the result of a ref or nodeset on the action.

This is the same context used to evaluate the context attribute on insert/delete.

For this reason, the 'if' expression in the example you cited is actually correct.  In fact, the example is written this way exactly to highlight the difference.

The context coming into the setvalue is the 'default' instance.  The bulk of the action script does work in a 'temp' instance.  In the setvalue you cited, the one which adds to the accumulator, the 'value' attribute must directly reference the default instance because its evaluation context comes from the ref attribute, which refers to a node in the temp instance.  But the 'if' attribute is evaluated before the 'ref' so it uses the in-scope evaluation context, which is the default instance in this example.

Cheers,
John M. Boyer, Ph.D.
Senior Technical Staff Member
Lotus Forms Architect and Researcher
Chair, W3C Forms Working Group
Workplace, Portal and Collaboration Software
IBM Victoria Software Lab
E-Mail: boyerj@...  

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

Nick_Van_den_Bleeken@...
Sent by: www-forms-editor-request@...

12/14/2007 07:02 AM

To	public-xforms@..., www-forms-editor@...
cc
Subject	Wrong XPath expression in Iterate example of XForms 1.1 CR

All,

Can it be that the 'if' XPath expression of the 3th setvalue in the 'Summing Selected Results'  sample [1] is missing an explicit reference to the default instance?

<trigger>
 <label>Get Sum</label>
 <action ev:event="DOMActivate">
    <setvalue ref="instance('temps')/counter" value="1"/>
    <setvalue ref="instance('temps')/accumulator" value="0"/>
    <action while="instance('temps')/counter <= count(/some/nodes)">
       <setvalue ref="instance('temps')/accumulator"
                 value=". + instance('default')/some/nodes[number(instance('temps')/counter)]"
                 if="boolean-from-string(/some/nodes[number(instance('temps')/counter)]/@selected)"/>
       <setvalue ref="instance('temps')/counter" value=". + 1"/>
    </action>
 </action>
</trigger>

The ref of the 3th setvalue changes the instance of the in-scope evaluation context to instance 'temps'.
But the '/some/nodes' are in the 'default' instance (see value of the setvalue).
-> we should change 'boolean-from-string(/some/nodes' to
    'boolean-from-string(instance('default')/some/nodes'


Regards,


Nick Van den Bleeken  -  Research & Development Manager
Inventive Designers
Phone: +32 - 3 - 8210170
Fax: +32 - 3 - 8210171
Email: Nick_Van_den_Bleeken@...

1: http://www.w3.org/TR/xforms11/#action-iterated

Inventive Designers' Email Disclaimer:http://www.inventivedesigners.com/email-disclaimer