Since software systems are becoming increasingly more concurrent and distributed, modeling and analysis of interactions among their components is a crucial problem. In several application domains, message-based communication is used as the interaction mechanism, and the communication contract among the components of the system is specified semantically as a state machine. In the service-oriented computing domain this type of message-based communication contracts are called “choreography” specifications. A choreography specification identifies allowable ordering of message exchanges in a distributed system. A fundamental question about a choreography specification is determining its realizability, i.e., given a choreography specification, is it possible to build a distributed system that communicates exactly as the choreography specifies? In this short paper we give an overview of this problem, summarize some of the recent results and discuss its application to web service choreographies, Singularity OS channel contracts, and UML collaboration (communication) diagrams.