PREFIX ical: <http://www.w3.org/2002/12/cal/icaltzd#>
PREFIX xs: <http://www.w3.org/2001/XMLSchema#>

SELECT ?start1 ?stop1 ?loc1 ?summ1 ?summ2 ?summ3

FROM <http://pagesperso-systeme.lip6.fr/Jean-Francois.Perrot/inalco/XML/RDF/MicroFormats/ExRDFa/Jane/Jane.xml>
FROM <http://pagesperso-systeme.lip6.fr/Jean-Francois.Perrot/inalco/XML/RDF/MicroFormats/EmbedRDF/David.xml>
FROM <http://pagesperso-systeme.lip6.fr/Jean-Francois.Perrot/inalco/XML/RDF/MicroFormats/hCalendar/Robin.xml>

WHERE
  { 
	?event1 a ical:Vevent;
              ical:summary ?summ1 ;
  	      ical:dtstart ?start1 ;
              ical:dtend ?stop1 ;
              ical:location ?loc1.
  	?event2 a ical:Vevent;
              ical:summary ?summ2 ;
  	      ical:dtstart ?start2;
              ical:dtend ?stop2;
              ical:location ?loc2.
  	?event3 a ical:Vevent;
              ical:summary ?summ3 ;
  	      ical:dtstart ?start3;
              ical:dtend ?stop3;
              ical:location ?loc3.
      FILTER (  ?event1 != ?event2 &&  ?event2 != ?event3  &&  ?event1 != ?event3  ) .
      FILTER ( xs:string(?start1) = xs:string(?start2) ).
      FILTER ( xs:string(?stop1) = xs:string(?stop2) ).
      FILTER ( xs:string(?loc1) = xs:string(?loc2) ).
      FILTER ( xs:string(?start1) = xs:string(?start3) ).
      FILTER ( xs:string(?stop1) = xs:string(?stop3) ).
      FILTER ( xs:string(?loc1) = xs:string(?loc3) ).
      FILTER ( xs:string(?start3) = xs:string(?start2) ).
      FILTER ( xs:string(?stop3) = xs:string(?stop2) ).
      FILTER ( xs:string(?loc3) = xs:string(?loc2) ).
      FILTER ( xs:string(?summ1) <= xs:string(?summ2) ). 
      FILTER ( xs:string(?summ2) <= xs:string(?summ3) ).
}