code: QueryInfo registerSearch(String appIdentifier,
  			SPFSearchDescriptor searchDescriptor, SPFSearchCallback callback) {
  		// convert SearchDescriptor to internal representation
  		// register the query and return the assigned id
  		QueryInfo queryInfo = QueryInfo.create(appIdentifier, searchDescriptor);
  		String queryId = generateQueryId(queryInfo);
  		queries.put(queryId, queryInfo);
  		performer.registerSearchCallback(callback, queryInfo);
  		log(TAG, "registering query with queryId: " + queryId);
  		return queryInfo;
  	}
docs: Registers and starts the search operation as specified in queryInfo.
  @param callback
  
  @param queryInfo
  @return the query id