Orbeon dynamic dropdown linked to another field - orbeon

Question

A variation on the sample dynamic dropdown sample using Form Builder, how does one refer the drop down list to the value of another field. I can get the 'debug' text field to change with ../pet , but the item[#group=context()/../pet] is not working as expected.
Note: The 'petnames' model is included but I could not reference it internally so I reference to an external XML file of the same format.
<xh:html xmlns:xh="http://www.w3.org/1999/xhtml"
xmlns:xxi="http://orbeon.org/oxf/xml/xinclude"
xmlns:ev="http://www.w3.org/2001/xml-events"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:saxon="http://saxon.sf.net/"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:fb="http://orbeon.org/oxf/xml/form-builder"
xmlns:xxf="http://orbeon.org/oxf/xml/xforms"
xmlns:sql="http://orbeon.org/oxf/xml/sql"
xmlns:fr="http://orbeon.org/oxf/xml/form-runner"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xf="http://www.w3.org/2002/xforms"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:exf="http://www.exforms.org/exf/1-0"
fr:data-format-version="4.0.0">
<xh:head>
<xh:title>Example Dynamic data dropdown</xh:title>
<xf:model id="fr-form-model" xxf:expose-xpath-types="true">
<!-- Main instance -->
<xf:instance id="fr-form-instance" xxf:exclude-result-prefixes="#all" xxf:index="id">
<form>
<section-1>
<pet/>
<control-4/>
<mypetname itemset-empty="true"/>
</section-1>
</form>
</xf:instance>
<xf:instance id="petnames">
<root>
<item group="cat" value="Kitty"/>
<item group="cat" value="Garfield"/>
<item group="dog" value="Spot"/>
<item group="dog" value="Rover"/>
<item group="fish" value="Bubbles"/>
<item group="fish" value="Bob"/>
<item group="cobra" value="King"/>
<item group="cobra" value="Shelby"/>
</root>
</xf:instance>
<!-- Bindings -->
<xf:bind id="fr-form-binds" ref="instance('fr-form-instance')">
<xf:bind id="section-1-bind" name="section-1" ref="section-1">
<xf:bind id="pet-bind" ref="pet" name="pet"/>
<xf:bind id="mypetname-bind" ref="mypetname" name="mypetname"/>
<xf:bind id="control-4-bind" ref="control-4" name="control-4" xxf:whitespace="trim"
calculate="../pet"/>
</xf:bind>
</xf:bind>
<!-- Metadata -->
<xf:instance xxf:readonly="true" id="fr-form-metadata" xxf:exclude-result-prefixes="#all">
<metadata>
<application-name>samples</application-name>
<form-name>DynamicDataDropdown</form-name>
<title xml:lang="en">Example Dynamic data dropdown</title>
<description xml:lang="en"/>
</metadata>
</xf:instance>
<!-- Attachments -->
<xf:instance id="fr-form-attachments" xxf:exclude-result-prefixes="#all">
<attachments>
<css mediatype="text/css" filename="" size=""/>
<pdf mediatype="application/pdf" filename="" size=""/>
</attachments>
</xf:instance>
<!-- All form resources -->
<xf:instance xxf:readonly="true" id="fr-form-resources" xxf:exclude-result-prefixes="#all">
<resources>
<resource xml:lang="en">
<pet>
<label>Pick a pet</label>
<hint/>
<item>
<label>Cat</label>
<value>cat</value>
</item>
<item>
<label>Dog</label>
<value>dog</value>
</item>
<item>
<label>Fish</label>
<value>fish</value>
</item>
<item>
<label>Cobra</label>
<value>cobra</value>
</item>
</pet>
<control-4>
<label>debug</label>
<hint/>
</control-4>
<mypetname>
<label>Your pet names</label>
<hint/>
</mypetname>
<section-1>
<label>Untitled Section</label>
</section-1>
</resource>
</resources>
</xf:instance>
</xf:model>
</xh:head>
<xh:body>
<fr:view>
<fr:body xmlns:p="http://www.orbeon.com/oxf/pipeline" xmlns:xbl="http://www.w3.org/ns/xbl"
xmlns:oxf="http://www.orbeon.com/oxf/processors">
<fr:section id="section-1-control" bind="section-1-bind">
<xf:label ref="$form-resources/section-1/label"/>
<fr:grid>
<xh:tr>
<xh:td>
<xf:select1 id="pet-control" bind="pet-bind" appearance="dropdown">
<xf:label ref="$form-resources/pet/label"/>
<xf:hint ref="$form-resources/pet/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
<xf:itemset ref="$form-resources/pet/item">
<xf:label ref="label"/>
<xf:value ref="value"/>
</xf:itemset>
</xf:select1>
</xh:td>
<xh:td>
<xf:input id="control-4-control" bind="control-4-bind">
<xf:label ref="$form-resources/control-4/label"/>
<xf:hint ref="$form-resources/control-4/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
</xf:input>
</xh:td>
<xh:td>
<fr:databound-select1 xmlns="http://orbeon.org/oxf/xml/form-builder"
xmlns:xxbl="http://orbeon.org/oxf/xml/xbl"
id="mypetname-control"
resource="http://192.168.0.80/petnames.xml"
bind="mypetname-bind">
<xf:label ref="$form-resources/mypetname/label"/>
<xf:hint ref="$form-resources/mypetname/hint"/>
<xf:alert ref="$fr-resources/detail/labels/alert"/>
<xf:itemset ref="/root/item[#group=context()/../pet]">
<xf:label ref="#value"/>
<xf:value ref="#value"/>
</xf:itemset>
</fr:databound-select1>
</xh:td>
</xh:tr>
</fr:grid>
</fr:section>
</fr:body>
</fr:view>
</xh:body>
</xh:html>

Answer 1

You can use the following:
<xf:itemset ref="/root/item[#group = xxf:instance('fr-form-instance')/section-1/pet]">
In this case, context() won't work because the XPath expression in the ref is evaluated inside the XBL component, and doesn't have access to what's outside of the component. In some cases however, it is useful to break the encapsulation, and for those cases the extension function xxf:instance() allows you to do so.