XQuery/SPARQL interface

< XQuery

The following script provides, via a Joseki server at UWE, a query interface to RDF. Literal language and datatype are ignored in this representation. URIs link to the browse query and also directly to the resource.

A function converts the SPARQL XML Query result to a table, with links.

declare function fr:sparql-to-table($rdfxml,$script-name ) {
(: literal language and datatype ignored in this representation.  URI links to the browse query and directly to the resource are generated :)
    let $vars := $rdfxml//sr:head/sr:variable/@name
    return
  <table border="1">
    <tr>
      {for $var in  $vars
         return
          <th>{string($var)}</th>
      }
    </tr>
    { for  $row in $rdfxml//sr:results/sr:result
     return
     <tr>
            { for $var in $vars
              let $binding  := $row/sr:binding[@name=$var]/*          
              return                
                 <td>
                  {  typeswitch ($binding)
                        case element(sr:uri)  return
                           (<a href="{$script-name}?uri={string($binding)}">{ string($binding) }</a>,  
                            <a href="{string($binding)}"> ^ </a> 
                            )                            
                       case element(sr:literal) return
                          string($binding)    
                       case element (sr:bnode) return
                           concat("_:",$binding)
                        default  return
                            ()
                    }
                 </td>
             }
      </tr>
      }
   </table>
 };

The SPARQL interface uses the configuration file to declare the namespaces.

import module namespace fr="http://www.cems.uwe.ac.uk/wiki/fr"   at  "fr.xqm";
declare namespace rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";
declare namespace rdfs = "http://www.w3.org/2000/01/rdf-schema#";

declare option exist:serialize "method=xhtml media-type=text/html omit-xml-declaration=no indent=yes 
        doctype-public=-//W3C//DTD&#160;XHTML&#160;1.0&#160;Transitional//EN
        doctype-system=http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";
        
declare variable $config-file := request:get-parameter("config", "/db/Wiki/RDF/empdeptconfig.xml");
declare variable $config := doc($config-file);
declare variable $graph :=  concat("http://www.cems.uwe.ac.uk/xmlwiki/RDF/xml2rdf.xq?config=",$config-file);
declare variable $default-engine := "http://www.cems.uwe.ac.uk/joseki/sparql";
declare variable $script-name :=   tokenize(request:get-uri(),'/')[last()];
declare variable $default-prolog :=
"PREFIX fn: <http://www.w3.org/2005/xpath-functions#>
PREFIX afn: <http://jena.hpl.hp.com/ARQ/functions#>
";

declare variable $browse := "select ?s ?p ?o 
where {
      {<uri> ?p ?o }
      UNION
      {?s ?p <uri>}
      UNION
      {?s <uri> ?o}
   }";
   
let $config-prolog := fr:sparql-prefixes($config)
let $query := request:get-parameter ("query",())
let $uri := request:get-parameter("uri",())   
let $engine := request:get-parameter("engine",$default-engine)
let $query := 
   if ($uri)
   then  replace($browse,"uri",$uri)
   else $query
   
let $queryx := concat($default-prolog,$config-prolog,$query)
let $sparql := concat($engine,
                      "?default-graph-uri=",$graph,
                      "&amp;query=",encode-for-uri($queryx) 
                     )
let $result  :=
       if ($query !="")
       then
          fr:sparql-to-table(doc($sparql), $script-name) 
       else ()
return
<html xmlns="http://www.w3.org/1999/xhtml">
   <head> 
      <title>Emp-dept Query</title>
   </head>
   <body>
      <h1>Emp-dept Query</h1>
      <form action="{$script-name}">
          <textarea name="query" rows ="8" cols="90">
             {$query}
        </textarea>
        <br/>
        <input type="submit"/>
     </form>
     <h2>Result</h2>
         {$result}
    </body>
</html>

Application

Query

The interface expands a query like

  select ?name ?job where {
   ?emp rdf:type  f:emp.
   ?emp foaf:surname ?name.
   ?emp f:Job ?job.
  }

into:

 prefix foaf: <http://xmlns.com/foaf/0.1/>
 prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
 prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
 prefix f: <http://www.cems.uwe.ac.uk/xmlwiki/empdept/concept/>
 prefix xs: <http://www.w3.org/2001/XMLSchema#>
 select ?name ?job 
 from <http://www.cems.uwe.ac.uk/xmlwiki/RDF/xml2rdf.xq?config=/db/Wiki/RDF/empdeptconfig.xml">
 where {
   ?emp rdf:type  f:emp.
   ?emp foaf:surname ?name.
   ?emp f:Job ?job.
 }

and sends this to the Joseki service. The graph to query is actually passed as the default graph rather than in the from clause.

To do

handle language and datatype
local URIs as local names rather than full URIs#
better handling of default graph - should be able to reference the cached rdf defined in the config file

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