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 XHTML 1.0 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=",$graph, "&query=",encode-for-uri($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
[edit | edit source]
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
[edit | edit source]- 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