DDS11 — (R#150) Ambiguous description of create_topic behavior

The description of the DomainParticipant::create_topic operation in section 2.1.2.2.1.5 states that if an existing topic is found with the same name and QoS, that Topic will be returned; no duplicate Topic will be created. However, the specification fails to describe what will happen in the event that the name and QoS match but the listener is different. Additionally, the behavior places a barrier of understanding before the user, because create_topic behaves differently from all other factory methods in this respect.

Proposed Resolution:

Revise the specification to remove the language about reusing Topics. The create_topic operation, like all other 'create' operations in the specification, should always return a new Topic.

Proposed Revised Text:

Section 2.1.2.2.1.5 contains the following paragraphs; they should both be stricken from the specification:

The implementation of create_topic will automatically perform a lookup_topicdescription for the specified topic_name. If a Topic is found, then the QoS and type_name of the found Topic are matched against the ones specified on the create_topic call. If there is an exact match, the existing Topic is returned. If there is no match the operation will fail. The consequence is that the application can never create more than one Topic with the same topic_name per DomainParticipant. Subsequent attempts will either return the existing Topic (i.e., behave like find_topic) or else fail.

If a Topic is obtained multiple times by means of a create_topic, it must also be deleted that same number of times using delete_topic.

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