code: @Override
      public boolean serviceExists(URI serviceUri) throws ServiceException {
          if (serviceUri == null || !serviceUri.isAbsolute()) {
              log.warn("The Service URI is either absent or relative. Provide an absolute URI");
              return false;
          }
  
          URI graphUri;
          try {
              graphUri = getGraphUriForElement(serviceUri);
          } catch (URISyntaxException e) {
              log.warn("The namespace of the URI of the message content is incorrect.", e);
              return Boolean.FALSE;
          }
  
          if (graphUri == null) {
              log.warn("Could not obtain a graph URI for the element. The URI may not be managed by the server - " + serviceUri);
              return Boolean.FALSE;
          }
  
          String queryStr = new StringBuilder()
                  .append("ASK { \n")
                  .append("GRAPH <").append(graphUri.toASCIIString()).append("> {")
                  .append("<").append(serviceUri.toASCIIString()).append("> <").append(RDF.type.getURI()).append("> <").append(MSM.Service).append("> }\n}").toString();
  
          Query query = QueryFactory.create(queryStr);
          QueryExecution qe = QueryExecutionFactory.sparqlService(this.graphStoreManager.getSparqlQueryEndpoint().toASCIIString(), query);
          MonitoredQueryExecution qexec = new MonitoredQueryExecution(qe);
          try {
              return qexec.execAsk();
          } finally {
              qexec.close();
          }
      }
docs: Determines whether a service is known to the registry
  
  @param serviceUri the URI of the service being looked up
  @return True if it is registered in the server
  @throws uk.ac.open.kmi.iserve.sal.exception.ServiceException