The purpose of flink-contrib currently is to hold contributions to the project that we do not consider part of the core flink functionality, but provide useful tools around it. In general code placed here has to meet less requirements in terms of covering all corner cases if it provides a nice solution for a set of well defined problems.
As of today it has two small utilities, the TweetInputFormat (by Mustafa Elbehery) and the collect functionality for the DataStream (by Gabor Gevay). The pull request for the Storm compatibility layer (by Matthias J. Sax) [1] raises the issue as it is way more code to maintain and is more complex in general that how the community would like to handle these in terms of distribution. Do we want to have it in the Flink repository or maybe in a separate one. I am personally really for having the Storm compatibility layer under flink-contrib as Matthias is very active on the mailing list and has also expressed his interest of further developing the functionality of the compatibility layer. To top that a couple of users got excited about the new feature, so I see no risk in having this code in the main repository. As for the structure of flink-contrib I would have the contents separated to slim as possible maven projects, to make sure that the users only get the dependencies that they really need. [1] https://github.com/apache/flink/pull/573
