A condition is an XSLT map that will be applied to the source envelope of the step. A simple condition has to return true or false in xml format:

<result>
    true
</result>

A condition XSLT example:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
        <result>
            <xsl:choose>
                <xsl:when test="envelope/documents/document[@id='document_id']/field[@name='field_name'] &gt; 0">
                    true
                </xsl:when>
                <xsl:otherwise>
                    false
                </xsl:otherwise>
            </xsl:choose>
        </result>
    </xsl:template>
</xsl:stylesheet>