Function concat() can stick several strings together : concat « XSLT stylesheet « XML Tutorial

1. XML Tutorial
2. XSLT stylesheet
3. concat

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<data>
    <user firstName="John" surname="Smith"/>
    <user firstName="Joe" surname="Smith"/>
    <user firstName="Charles" surname="Smith"/>
</data>
File: Transform.xslt

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
      version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="//user">
      <Paragraph>
        <xsl:value-of select="concat(@firstName,' ',@surname)"/>
      </Paragraph>
    </xsl:template>
</xsl:stylesheet>

Output:
<?xml version="1.0" encoding="UTF-8"?>
    <Paragraph>John Smith</Paragraph>
    <Paragraph>Joe Smith</Paragraph>
    <Paragraph>Charles Smith</Paragraph>