The query processor locates the objects in its host entity, and performs the requested operations. Care has been taken to use a limited set of the ASN.1 coding set, so that query processor's handling of data can be optimized. It is a key feature of HEMS that messages to the query processor contain multiple instructions. The authors felt that this would give much higher performance than a remote procedure system which limited an application to one operation per message. The set of maintained objects is standardized across all entities.
Every entity is required to manage a small set of objects.
Entities are also permitted to make additional, entity-specific objects available to applications. A method for discovering the existence of additional objects is defined. The combination of self-describing data, the ability to add to the standard data set, and a query language which can be easily enhanced appeared to offer the necessary extensibility. On many network entities, particularly critical network components such as gateways, it is necessary to have a way for the devices to send unsolicited status messages to network management centers. In the HEMS system, events are handled as slightly specialized replies to queries, and are sent to one or more management centers.