Communiqué is a library for planning messages in sequence diagrams written in Ruby.
It resulted from the research I did for my Computer Science MS Thesis, which is titled Planning-Based Approach for Automating Sequence Diagram Generation. The basic idea is simple: under the right conditions, generating UML sequence diagrams is essentially a planning problem in disguise.
The "right conditions" are when use cases and class diagrams are developed using the Design by Contract approach. When that is the case, generating the sequence diagrams based on the other two models starts to look very similar to solving a planning problem. In both cases, and despite some differences in terminology, the same building blocks are present.
We provide more details about the basic idea along with a simple illustrative example in our DMS 2012 paper, Automating UML Sequence Diagram Generation by Treating it as a Planning Problem, which represents the early stages of our research before we started developing Communiqué. Much more details about Communiqué and the research behind it are available in my thesis, which I will post a link to here once it gets officially approved.