Mapping of DCPS Entities to DDSI Entities

Each DCPS domain participant in a domain has a corresponding DDSI participant. These DDSI participants drive the discovery of participants, readers, and writers via the discovery protocols (Discovery behaviour). By default, each DDSI participant has a unique address on the network in the form of its own UDP/IP socket with a unique port number.

Any DataReader or DataWriter created by a DCPS domain participant has a corresponding DDSI reader or writer (referred to as endpoints). However, there is no one-to-one mapping. In DDSI:

• a reader is the combination of DCPS DataReader and the DCPS subscriber it belongs to,

• a writer is a combination of DCPS DataWriter and DCPS publisher.

There are no standardized built-in topics for describing DCPS subscribers and publishers. However, there are non-standard extensions that enable implementations to offer additional built-in topics to represent these entities and include them in the discovery.

In addition to the application-created readers and writers, DDSI participants have several DDSI built-in endpoints for discovery and liveliness checking/asserting.

If there are no corresponding endpoints, a DDSI implementation can exclude a participant. For example, if a participant does not have writers, there is no need to include the DDSI built-in endpoints for describing writers, nor the DDSI built-in endpoint for learning of readers of other participants.