here The OMG DDS standard has been designed to effectively support statically defined data models. This assumption ensures that topics data types are known at compile time, that every member of the DDS global data space agrees precisely on the same topic-type association, and that extensions are captured by either DLRL classes inheritance, or by DCPS IS-A relations. Although this model allows for good properties such as static type checking and very efficient, low-overhead, implementation of the standard it also suffers a few drawbacks. Namely, it is hard to cope with data models evolving over time unless all the elements of the system are upgraded consistently. It is also complex to deal with dynamically defined topics, although in some case this is achievable by means of proprietary APIs.
These limitation are currently being addressed in the scope of the OMG RFP mars/2008-05-03, which is looking to extend the DDS standard with the following features:
• Extensible Topic Type System. This will define an abstract type system for DDS Topics Type, that shall provide built-in support for extensibility, as well as support for complex types such as object maps, and sparse data.
• Dynamic DDS API. A Dynamic DDS API, to be used as an alternative to existing API, that shall allow to define, read, take, access, and write, Topics whose types are not know at compile time.
• Data Encapsulation Format. New data encapsulation format, or extend existing, so to efficiently support extensible and dynamic types.
The RFP is available here.
Cheers,
@angelo
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