anchor.diff:  ....
   +
   Note that $COUNT represents the number of total statements retrieved by
  -Listing <<query_for_number_of_statements>>.
  +Listing <<query_for_number_of_statements, 1>>.
   +
   Note that Virtuoso has trouble to count the number of statements. So
   this adhoc procedure does not work well for the endpoint based on
  
positive.code: 1.  Classes
  +
  We retrieve a list of classes using a query described in Listing
  <<query_for_classes_on_a_graph>> and
  <<query_for_classes_having_instances_on_a_graph>>.
  +
  [[query_for_classes_on_a_graph]]
  .Obtain the classes on a graph g
  ....
  PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
  PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
  
negative.code: Performace suggests how powerful the endpoint is.
  
  We measure the response times of the two queries, Listing
  <<query_ask, 15>>, <<query_for_list_of_graphs, 16>>. 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.
  
  [[query_ask]]
  .Listing 15. A Most Simple Query
  ....
  ASK {}
  
  ....
  
  [[query_for_list_of_graphs]]
  .Listing 16. A Query for Listing Graphs
  ....
  SELECT DISTINCT
    ?g
  