Super simple example of a dynamic dropdown with values ranging from 1 to a configurable maximum

form.xhtml

<xh:html xmlns:xf="http://www.w3.org/2002/xforms"
    xmlns:xh="http://www.w3.org/1999/xhtml"
    xmlns:ev="http://www.w3.org/2001/xml-events">

    <xh:head>
        <xf:model>
            <xf:instance id="instance">
                <form>
                    <value>1</value>
                    <max>9</max>
                </form>
            </xf:instance>
        </xf:model>
    </xh:head>
    <xh:body>
        <xf:select1 ref="value">
            <xf:itemset ref="1 to ../max">
                <xf:label value="."/>
                <xf:value value="."/>
            </xf:itemset>
        </xf:select1>

        <xf:trigger>
            <xf:label>Increase</xf:label>
            <xf:setvalue ev:event="DOMActivate" ref="max" value=". + 1"/>
        </xf:trigger>

        <xf:trigger>
            <xf:label>Decrease</xf:label>
            <xf:setvalue ev:event="DOMActivate" ref="max" value=". - 1"/>
        </xf:trigger>

    </xh:body>
</xh:html>

This is a super simple example of a dynamic dropdown with values ranging from 1 to a configurable maximum.

There are two interesting bits in that line:

<xf:itemset ref="1 to ../max">

First, we use @ref instead of @nodeset. The XForms Working Group recently proposed to deprecate @nodeset (for several reasons) and now recommends experimenting with using @ref instead. But you could use @nodeset as well and it wouldn't make a difference.

Second is the XPath expression. This is an XPath 2.0 expression expressing a range of number values from 1 to whatever the value of ../max is.

Supporting atomic values (as in the number "1") in xf:itemset is an Orbeon Forms extension. It makes sense for XPath 2.0-aware implementations to support this though, and we hope that along with XPath 2.0 support in XForms 1.2, this will be standardized as well.