Possible to set two values for two different nodes from user input in XForms?

I would like to set two values for two different nodes from user input in XForms. I am curious about how this is done, if at all possible.

For example, if I have the following data model:

<xf:instance id="criteria_data" xmlns="">
    <criteria>
        <set>
           <root></root>
           <criterion></criterion>
        </set>
    </criteria>
</xf:instance>

<xf:instance id="choices" xmlns="">
    <choices>
        <root label="The Choices">/AAA</root>
        <choice label="BBB">/@BBB</choice>
    </choices>
</xf:instance>

<xf:instance id="choices" xmlns="">
    开发者_如何学编程<choices>
        <root>/AAA</root>
        <choice label="BBB">/@BBB</choice>
        <choice label="CCC">/@CCC</choice>
    <choices>
</xf:instance>

<xf:bind id="data_criterion" nodeset="instance('criteria_data')/criteria/set/criterion"/>         
<xf:bind id="data_root" nodeset="instance('criteria_data')/criteria/set/root"/>
<xf:bind id="choices_root" nodeset="instance('choices')/root"/>
<xf:bind id="choices" nodeset="instance('choices')/choice"/>

and my ui code looks like:

<xf:select bind="data_criterion" appearance="full">
    <xf:label>Your choices:</xf:label>    
    <xf:itemset bind="choices">
       <xf:label ref="@label"></xf:label>
       <xf:value ref="."></xf:value>
    </xf:itemset>
</xf:select>    

But I essentially want it to be like this (though this is invalid and does not produce any xml at all):

<xf:select appearance="full">
    <xf:label>Your choices:</xf:label>    
    <xf:itemset bind="choices">
        <xf:label ref="@label"></xf:label>
        <xf:value bind="data_criterion" ref="."></xf:value>
        <xf:value bind="data_root" ref="instance('choices')/root"></xf:value>
    </xf:itemset>
</xf:select>    

The XML output I want to achieve (if user checks "BBB"):

<criteria>
    <set>
       <root>/AAA</root>
       <criterion>/@BBB</criterion>
    </set>
</criteria>

How can I achieve setting these two nodes for the one checkbox seletion?

Hope that all made sense...

Thanks! :)

You should declare specific actions, such as "xf:setvalue", to be done on event "xforms-select".

-Alain

You could also use calculate:

<xf:bind nodeset="instance('criteria_data')/criteria/set/root" calculate="instance
('choices')/choice[. = instance('criteria_data')/criteria/set/criterion]/../root">