anchor.diff:  
   ....
   +
  +[[query_for_classes_having_instances_on_a_graph]]
  +.Obtain the classes having instances on a graph g
   ....
   PREFIX rdf:
   SELECT DISTINCT ?c
  
positive.code: Performace suggests how powerful the endpoint is.
  
  We measure the response times of the two queries, Listing
  [list:query_ask], [list:query_for_list_of_graphs]. The former query is a
  most simple query and we use this query to estimate the transfer time.
  The latter query requires a little computations for endpoints. We
  believe the execution cost of this query does not differ very much
  according to the size of data.
  
  ....
  ASK {}
  
  ....
  
  ....
  SELECT DISTINCT
    ?g
  
negative.code: 4.  Properties
  +
  We retrieve a list of properties using a query described in Listing
  <<query_for_properties_on_a_graph>>.
  +
  [[query_for_properties_on_a_graph]]
  .Obtain the properties on a graph g
  ....
  SELECT DISTINCT ?p
          FROM <g>
  