VirtSPARQLXSLT Guide to using SPARQL inside XSLT Guide to using SPARQL inside XSLT This guide demonstrates how Virtuoso allows SPARQL queries to be embedded into an XSLT style sheet, and executed against a remote SPARQL endpoint (here, we use the LOD Cloud Cache) to retrieve data for use in HTML output. Implementation The key component of this feature is the <xsl:for-each-row> control element. This element has one attribute, named either "sparql" or "sql"; the value of the attribute is an XPath expression that returns the text of the query to executed, e.g., <xsl:for-each-row sparql="string(\044query)"> The XPath expression can be a plain string constant, but because the query can be quite long, it is usually more convenient to store the text in a variable and refer to that variable. The SPARQL query may contain parameters (written in the form ?:name). A parameter of this sort will get its value from the XSLT variable $name. (If there is any nesting or recursion, the value(s) will come from the innermost variables.) The query execution in turn creates new XSLT variables that exist inside the body of <xsl:for-each-row>. Each result column of a query becomes one XSLT variable. The body of <xsl:for-each-row> is instantiated once for each row of the query result set, with new values for the variables in each instantiation. Example Execute from iSQL: SQL> xslt_sheet ('local://friends.xsl', xtree_doc ('<xsl:stylesheet xmlns:xsl = "" version = "1.0" xmlns:sample="http://xslt/" > <xsl:output method = "html" version="1.0" doctype-public="http://public" doctype-system="http://system" /> <xsl:param name="fname" select="''Kingsley''" /> <xsl:param name="lname" select="''Idehen''" /> <xsl:param name="fullname" select="''Kingsley Idehen''" /> <xsl:variable name = "query"> <![CDATA[ PREFIX foaf: <> SELECT DISTINCT ?maxlinkg ?fnick ?ffullname ?ffname ?flname ?fimg WHERE { SERVICE <> (DEFINE lang:dialect 65535) { { SELECT DISTINCT ?maxlinkg ?fg ?fnick ?ffullname ?ffname (bif:__max_notnull (?flname1, ?flname2)) AS ?flname ?fimg WHERE { { SELECT (MAX(?linkg)) AS ?maxlinkg ?f WHERE { { SELECT DISTINCT ?k WHERE { GRAPH ?kg { { ?k foaf:firstName ?:fname ; foaf:familyName ?:lname } UNION { ?k foaf:firstName ?:fname ; foaf:family_name ?:lname } UNION { ?k foaf:name ?:fullname } } } } GRAPH ?linkg { ?k foaf:knows ?f } } } GRAPH ?fg { ?f a <> . OPTIONAL { ?f foaf:firstName ?ffname } OPTIONAL { ?f foaf:nickname ?fnick } OPTIONAL { ?f foaf:name ?ffullname } OPTIONAL { ?f foaf:familyName ?flname1 } OPTIONAL { ?f foaf:family_name ?flname2 } OPTIONAL { ?f foaf:img ?fimg } } FILTER ( bound ( ?ffullname ) || ( bound ( ?ffname ) && ( bound ( ?flname1 ) || bound ( ?flname2 ) ) ) ) } ORDER BY ?fullname ?ffname } } } ]]></xsl:variable> <xsl:template match = "/"> <html><head>Simple demo for SPARQL inside XSLT</head> <body> <p>Known friends of <xsl:choose> <xsl:when test="\044fullname"><xsl:value-of select="\044fullname" /></xsl:when> <xsl:otherwise><xsl:value-of select="\044fname" /> <xsl:value-of select="\044lname" /></xsl:otherwise> </xsl:choose></p> <table> <xsl:for-each-row sparql="string(\044query)"> <tr><td><xsl:if test="\044fimg"><a href="{\044fimg}" ><img src="{\044fimg}" width="64" height="64" /></a></xsl:if></td> <td><a href=".?fname={\044ffname}&lname={\044flname}&fullname={\044ffullname}"> <b><xsl:choose> <xsl:when test="\044ffullname"><xsl:value-of select="\044ffullname" /></xsl:when> <xsl:otherwise><xsl:value-of select="\044ffname" /> <xsl:value-of select="\044flname" /></xsl:otherwise> </xsl:choose></b></a><br /> <xsl:if test="\044fnick">Nick: <xsl:value-of select="\044fnick" /><br /></xsl:if> (data from <a href="{\044maxlinkg}" ><xsl:value-of select="\044maxlinkg" /></a> <!-- and <a href="{\044maxfg}" ><xsl:value-of select="\044maxfg" /></a>-->) </td></tr> </xsl:for-each-row> </table> </body> </html> </xsl:template> </xsl:stylesheet>')); DB.DBA.VHOST_DEFINE ( lpath=>'/friends/', ppath => '/!friends/', is_dav => 1, vsp_user => 'dba', opts => vector('noinherit', 1) ); CREATE PROCEDURE WS.WS."/!friends/" ( INOUT path VARCHAR, INOUT params ANY, INOUT lines ANY ) { http_value (xslt ('local://friends.xsl', xtree_doc ('<fake />'), params)); } ; registry_set ('/!friends/', 'no_vsp_recompile') ; Go to http://cname/friends/, where results should look something like this: