DDS — Delete dependencies and semantics

Delete dependencies and semantics

***Ref-19 Delete_dependencies

Delete operations on Entities are only allowed if all other Entities
which have dependencies with it have been deleted first (for example,
a Topic may not be deleted before all other Entities depending on this
Topic have been deleted first)

The specification does not explain what happens if an application
tries to delete an entity that has dependent or contained entities.

This applies to Sections: 2.1.2.2.1.2, 2.1.2.2.1.4, 2.1.2.2.1.6,
2.1.2.2.1.8, 2.1.2.2.1.10, and 2.1.2.2.2.2.

Given that Topic object can be obtained by means of the
DomainParticipant::create_topic operation as well as the
DomainParticipant::lookup_topic operation there is an ambiguity
regarding the deletion of Topic objects prior to deleting the
DomainParticipant. Should the application call delete just on the ones
it obtained by means of "create_topic" or also on the ones obtained by
means of "lookup_topic"

**PROPOSAL**

State that if said "delete" operations are called while there are
dependent or contained entities the operation will fail and return
PRECONDITION_NOT_MET.

Fix by adding get_datareader() operation to the ReadCondition. This
operation should take no arguments and return a DataReader

Also state that the application should also delete the Topic obtained
by means of lookup_topic as this is needed to remote the local
resources devoted to it.

see below