The files here show some example queries based around the picture in the JPEG.

For now, the URIs are messed up (localhost is a bad domain name to use for universal identifiers!). But you can get the idea...

Dan


LOAD <http://localhost/notube/layer3.rdf>

SELECT * WHERE {  GRAPH ?g { ?s ?p ?o . } }


SELECT * WHERE { GRAPH  <http://localhost/notube/layerlist.rdf>{  ?s ?p ?o } }

# ask the layerlist which graph is from alice, then ask that about the school homepage claimed by alice:
#
PREFIX : <http://xmlns.com/foaf/0.1/>
SELECT ?x  WHERE {
  GRAPH  <http://localhost/notube/layerlist.rdf> { 
       <http://localhost/notube/layer1.rdf#alice> :made ?byalice .
    } 
 GRAPH ?byalice {
      <http://localhost/notube/layer1.rdf#alice> :schoolHomepage ?x .
  }
}

Answer: http://lookingglass.example.org/


Who says what about schoolHomepage? 

SELECT * WHERE { GRAPH ?g { ?s <http://xmlns.com/foaf/0.1/schoolHomepage> ?o . } }

According to the layerlist, who made the pages that tell us a schoolHomepage for Alice?

PREFIX : <http://xmlns.com/foaf/0.1/>
SELECT ?g ?who WHERE {
  GRAPH  <http://localhost/notube/layerlist.rdf> {  ?who :made ?g . }
  GRAPH  ?g {    <http://localhost/notube/layer1.rdf#alice> :schoolHomepage  <http://lookingglass.example.org/> .  }
}

or with names,

PREFIX : <http://xmlns.com/foaf/0.1/>
SELECT ?g ?who ?n WHERE {
  GRAPH  <http://localhost/notube/layerlist.rdf> {  ?who :made ?g . }
  GRAPH  ?g {    <http://localhost/notube/layer1.rdf#alice> :schoolHomepage  <http://lookingglass.example.org/> .  }
  OPTIONAL { ?who :name ?n }

Note the names here don't include those from Alice and Bob's files, since they are implied.

Let's find out what names there are for the school.

First, from its homepage. So let's ask: what URIs are there for the school whose homepage is Alice's 
schoolhomepage.

Starting with the school Alice says she goes to, ask what identifiers and names we find for it.

PREFIX : <http://xmlns.com/foaf/0.1/>
SELECT  *  WHERE {
  GRAPH  <http://localhost/notube/layer1.rdf> 
  { 
   <http://localhost/notube/layer1.rdf#alice> :schoolHomepage  ?x  .
  }
  GRAPH ?g 
  { 
    ?school :homepage ?x  .
    ?school :name ?n  .
  }
}