In view.xhtml:
My model looks like this:

                        <property>
                            <name>core.cygwin.home</name>
                            <value>C:/cygwin</value>
                        </property>


and xform-upload control is:
                                    <xforms:upload id="core.cygwin.home"
                                    navindex="4" ref="/product-state/properties/property[name='core.cygwin.home']/value">
                                    <xforms:label>Cygwin Installation Directory:</xforms:label>
                                    <xforms:filename ref="/product-state/properties/property[name='core.cygwin.home']/value"/>
                                    <xforms:help>Full path to the Cygwin installation directory (Windows only).</xforms:help>
                                    </xforms:upload>


and server generates this:

<label class=" xforms-label" for="core.cygwin.home">Cygwin Installation Directory:</label><span id="core.cygwin.home" class="xforms-control xforms-upload xforms-upload-state-file"><input class="xforms-upload-select" type="file" name="core.cygwin.home" unselectable="on" tabindex="4"><span class="xforms-upload-info"><span class="xforms-upload-filename">C:/cygwin</span><span class="xforms-upload-mediatype"></span><span class="xforms-upload-size"></span><img class="xforms-upload-remove" src="/elmpoc/orbeon/ops/images/xforms/remove.gif" alt="Remove File" title="Remove File"></span></span><img class=" xforms-help-image" src="/elmpoc/orbeon/ops/images/xforms/help.png" title="" alt=""><label class=" xforms-help" for="core.cygwin.home">Full path to the Cygwin installation directory (Windows only).</label>