VirtSPARQLXSLT

<docbook><section><title>VirtSPARQLXSLT</title><title> Guide to using SPARQL inside XSLT</title> Guide to using SPARQL inside XSLT
<para>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 <ulink url="http://lod.openlinksw.com/sparql/">LOD Cloud Cache</ulink>) to retrieve data for use in HTML output.</para>
<bridgehead class="http://www.w3.org/1999/xhtml:h2">Implementation</bridgehead>
<itemizedlist mark="bullet" spacing="compact"><listitem>The key component of this feature is the &lt;xsl:for-each-row&gt; control element.
 This element has one attribute, named either &quot;sparql&quot; or &quot;sql&quot;; the value of the attribute is an XPath expression that returns the text of the query to executed, e.g., <programlisting>&lt;xsl:for-each-row sparql=&quot;string(\044query)&quot;&gt;
</programlisting></listitem>
<listitem>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.
</listitem>
<listitem>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.) </listitem>
<listitem>The query execution in turn creates new XSLT variables that exist inside the body of &lt;xsl:for-each-row&gt;.
 Each result column of a query becomes one XSLT variable.
</listitem>
<listitem>The body of &lt;xsl:for-each-row&gt; is instantiated once for each row of the query result set, with new values for the variables in each instantiation.</listitem>
</itemizedlist><para> </para>
<bridgehead class="http://www.w3.org/1999/xhtml:h2">Example</bridgehead>
<orderedlist spacing="compact"><listitem>Execute from iSQL: <programlisting>SQL&gt;  xslt_sheet (&#39;local://friends.xsl&#39;, 
                  xtree_doc (&#39;&lt;xsl:stylesheet xmlns:xsl = &quot;http://www.w3.org/1999/XSL/Transform&quot; version = &quot;1.0&quot; xmlns:sample=&quot;http://xslt/&quot; &gt;
                              &lt;xsl:output method = &quot;html&quot; version=&quot;1.0&quot; doctype-public=&quot;http://public&quot; doctype-system=&quot;http://system&quot; /&gt;
                              &lt;xsl:param name=&quot;fname&quot; select=&quot;&#39;&#39;Kingsley&#39;&#39;&quot; /&gt;
                              &lt;xsl:param name=&quot;lname&quot; select=&quot;&#39;&#39;Idehen&#39;&#39;&quot; /&gt;
                              &lt;xsl:param name=&quot;fullname&quot; select=&quot;&#39;&#39;Kingsley Idehen&#39;&#39;&quot; /&gt;
                              &lt;xsl:variable name = &quot;query&quot;&gt;
&lt;![CDATA[
PREFIX foaf: &lt;http://xmlns.com/foaf/0.1/&gt;
SELECT DISTINCT ?maxlinkg 
                ?fnick 
                ?ffullname 
                ?ffname 
                ?flname 
                ?fimg 
WHERE
  {
    SERVICE &lt;http://lod.openlinksw.com/sparql/&gt; (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                 &lt;http://xmlns.com/foaf/0.1/Person&gt;
                .  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 ) 
                          &amp;&amp; ( bound ( ?flname1 ) 
                                  || bound ( ?flname2 ) 
                           ) ) )
          } 
          ORDER BY ?fullname 
                   ?ffname 
        } 
      } 
  }
]]&gt;&lt;/xsl:variable&gt;
&lt;xsl:template match = &quot;/&quot;&gt;
  &lt;html&gt;&lt;head&gt;Simple demo for SPARQL inside XSLT&lt;/head&gt;
    &lt;body&gt;
    &lt;p&gt;Known friends of &lt;xsl:choose&gt;
         &lt;xsl:when test=&quot;\044fullname&quot;&gt;&lt;xsl:value-of select=&quot;\044fullname&quot; /&gt;&lt;/xsl:when&gt;
         &lt;xsl:otherwise&gt;&lt;xsl:value-of select=&quot;\044fname&quot; /&gt; &lt;xsl:value-of select=&quot;\044lname&quot; /&gt;&lt;/xsl:otherwise&gt;
       &lt;/xsl:choose&gt;&lt;/p&gt;
    &lt;table&gt;
    &lt;xsl:for-each-row sparql=&quot;string(\044query)&quot;&gt;
      &lt;tr&gt;&lt;td&gt;&lt;xsl:if test=&quot;\044fimg&quot;&gt;&lt;a href=&quot;{\044fimg}&quot; &gt;&lt;img src=&quot;{\044fimg}&quot; width=&quot;64&quot; height=&quot;64&quot; /&gt;&lt;/a&gt;&lt;/xsl:if&gt;&lt;/td&gt;
      &lt;td&gt;&lt;a href=&quot;.?fname={\044ffname}&amp;lname={\044flname}&amp;fullname={\044ffullname}&quot;&gt;
      &lt;b&gt;&lt;xsl:choose&gt;
         &lt;xsl:when test=&quot;\044ffullname&quot;&gt;&lt;xsl:value-of select=&quot;\044ffullname&quot; /&gt;&lt;/xsl:when&gt;
         &lt;xsl:otherwise&gt;&lt;xsl:value-of select=&quot;\044ffname&quot; /&gt; &lt;xsl:value-of select=&quot;\044flname&quot; /&gt;&lt;/xsl:otherwise&gt;
       &lt;/xsl:choose&gt;&lt;/b&gt;&lt;/a&gt;&lt;br /&gt;
       &lt;xsl:if test=&quot;\044fnick&quot;&gt;Nick: &lt;xsl:value-of select=&quot;\044fnick&quot; /&gt;&lt;br /&gt;&lt;/xsl:if&gt;
       (data from &lt;a href=&quot;{\044maxlinkg}&quot; &gt;&lt;xsl:value-of select=&quot;\044maxlinkg&quot; /&gt;&lt;/a&gt; &lt;!-- and &lt;a href=&quot;{\044maxfg}&quot; &gt;&lt;xsl:value-of select=&quot;\044maxfg&quot; /&gt;&lt;/a&gt;--&gt;)
       &lt;/td&gt;&lt;/tr&gt;
    &lt;/xsl:for-each-row&gt;
    &lt;/table&gt;
    &lt;/body&gt;
  &lt;/html&gt;
&lt;/xsl:template&gt;
&lt;/xsl:stylesheet&gt;&#39;));

DB.DBA.VHOST_DEFINE 
  ( lpath=&gt;&#39;/friends/&#39;, 
    ppath =&gt; &#39;/!friends/&#39;, 
    is_dav =&gt; 1, 
    vsp_user =&gt; &#39;dba&#39;, 
    opts =&gt; vector(&#39;noinherit&#39;, 1)
  );

CREATE PROCEDURE WS.WS.&quot;/!friends/&quot; 
  ( INOUT  path    VARCHAR, 
    INOUT  params  ANY, 
    INOUT  lines   ANY
  )
{
  http_value (xslt (&#39;local://friends.xsl&#39;, xtree_doc (&#39;&lt;fake /&gt;&#39;), params));
}
;

registry_set (&#39;/!friends/&#39;, &#39;no_vsp_recompile&#39;)
;
</programlisting></listitem>
<listitem>Go to <ulink url="http://cname/friends/">http://cname/friends/</ulink>, where results should look something like this: <figure><graphic fileref="VirtSPARQLXSLT/xslt1.png" /></figure> <figure><graphic fileref="VirtSPARQLXSLT/xslt2.png" /></figure></listitem>
</orderedlist></section></docbook>