public Boolean dropGraph(String graphURI) {
		if(graphURI==null){
			log.warning("to be deleted Graph URI is null");
			return false;
		}
		String query = "DROP SILENT GRAPH <"+graphURI+">";
		if(autoCommit){
			return this.writeData(query.replace(" ", "+"));
		}
		this.queries += query.replace(" ", "+")+"\n";
		return null;
	}