code: @Override
      public Set<URI> listServices() {
          String queryStr = new StringBuilder()
                  .append("SELECT DISTINCT ?svc WHERE { \n")
                  .append(" GRAPH ?g { \n")
                  .append("?svc ").append("<").append(RDF.type.getURI()).append(">").append(" ").append("<").append(MSM.Service.getURI()).append("> . \n")
                  .append(" } \n")
                  .append("} \n")
                  .toString();
  
          return this.graphStoreManager.listResourcesByQuery(queryStr, "svc");
      }
docs: Obtains a list of service URIs with all the services known to the system
  
  @return list of URIs with all the services in the registry