swi_prolog_sparql_construct_error.pro

?- use_module(library(semweb/sparql_client)).        
true.

?- sparql_query('CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o } LIMIT 1', 
             Row, 
             [ host('localhost'), 
               path('/w/index.php/Special:SPARQLEndpoint'), 
               port(8080) ]).
ERROR: Domain error: `sparql_result_document' expected, found `'application/xml'' (<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">

  <rdf:Description rdf:about="http://localhost:8080/w/index.php?title=Special:URIResolver/Property-3AFoaf-3Aname">
    <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#ObjectProperty"/>
  </rdf:Description>

</rdf:RDF>)

Fixed now ... by setting Content-type: applixation/rdf+xml, not application/xml, in RDFIO