DDSPSMC11_ — Inheritance hierarchy of C++11 PSM conflicts with inheritance hierarchy from DDS PIM

In the DDS PIM the Topic inherits from two other classes: TopicDescription and Entity. However, in the C++11 PSM, this double inheritance relationship has been removed by making TopicDescription inherit from Entity, and making Topic only inherit from TopicDescription.

Although this seems to simplify the inheritance hierarchy, it has a couple of unwanted side-effects, since all TopicDescriptions are now Entities. That means that ContentFilteredTopic and MultiTopic now offer all the operations that an Entity normally offers:

• They have a StatusCondition
  • However, ContentFilteredTopic and MultiTopic have no statuses that are applicable to this StatusCondition.
• They offer an operation to extract their instance handle
  • However, ContentFilteredTopic and MultiTopic are not discoverable and therefore do not have an instance handle.
• Conceptually, Entities are supposed to offer Qos and Listeners, which ContentFilteredTopic and MultiTopic do not do.

We want to correct for this by removing the inheritance relationship between TopicDescription and Entity and reinstating the double inheritance for Topic on both TopicDescription and Entity.