Warning: unrecognized element xsl:variable online running saxon but not in Oxygen, why?

I have a schematron-file looking like this (as simply as possible)

    <sch:pattern id="TDOP_0400">
            <sch:rule context="//tekst:Kop">
                 <xsl:variable name="CONDITION"> 
                        <xsl:value-of select="tekst:Label and tekst:Opschrift and tekst:Nummer"/>
                 </xsl:variable>
            </sch:rule>
    </sch:pattern>

When I run it in Oxygen, it runs fine, but when I run it from the commandline I get an error. This is my commandline command:

$ java -cp ../saxon9.9.1.5/saxon9he.jar net.sf.saxon.Transform -t -s:tpod0400.sch -xsl:../saxon9.9.1.5/iso_svrl_for_xslt2.xsl -o:tpod0400.xsl

This is the error message, I get it for every xsl:variable-line:

Warning: unrecognized element xsl:variable

Solution

Best and most safe practice is to separate sch (schematron) from xslt code. Keep the sch-code inside the rule, and if you need xslt-functionality, break out with a function call to xslt-code, then return the result of the funtion back to the sch-code, and go on with sch-processing.

So short: Never mix up sch and xslt in one programming context, and you will always be safe.

I have an example, never mind what it does or what it is for, it is here to demonstrate how to break out an sch-context to invoke some xslt-code, and then return back to the sch-context:

<sch:pattern id="TPOD_0520">
    <sch:rule context="//tekst:Hoofdstuk/tekst:Titel">
        <sch:let name="APPLICABLE"
            value="$SOORT_REGELING = $OP or $SOORT_REGELING = $OV or $SOORT_REGELING = $WV"/>
        <sch:let name="hoofdstuk" value="string(../tekst:Kop/tekst:Nummer)"/>
        <sch:let name="titel" value="string(tekst:Titel/tekst:Kop/tekst:Nummer)"/>

<!-- Below is the break-out to XSLT, and the value coming from the function is used in the sch-code -->

        <sch:let name="volgorde" value="foo:volgordeTPOD_0520($titel, .)"/>
        <sch:let name="CONDITION" value="string-length($volgorde) = 0"/>
        <sch:assert test="($APPLICABLE and $CONDITION) or not($APPLICABLE)"> 
            TPOD_0520: Als tussen Hoofdstuk en Afdeling Titel voorkomt dan moet de nummering van Afdelingen beginnen met het samengestelde nummer van de Titel waarin de Afdeling voorkomt, gevolgd door een punt. (betreft hoofdstukken, titels, afdelingen):  <xsl:value-of select="$hoofdstuk"/>: <sch:value-of select="$titel"/>: <sch:value-of select="substring($volgorde,1,string-length($volgorde)-2)"/></sch:assert>
    </sch:rule>
</sch:pattern>

<xsl:function name="foo:volgordeTPOD_0520">
    <xsl:param name="titel" as="xs:string"/>
    <xsl:param name="context" as="node()"/>
    <xsl:variable name="volgorde">
        <xsl:for-each select="$context/tekst:Afdeling">
            <xsl:if test="not(string(tekst:Kop/tekst:Nummer)=concat($titel, '.', string(position())))">
                <xsl:value-of select="concat(string(tekst:Kop/tekst:Nummer),', ')"/>
            </xsl:if>
        </xsl:for-each>
    </xsl:variable>
    <xsl:value-of select="$volgorde"/>
</xsl:function>