Declarative Choreographies for Artifacts

A choreography models a collaboration among multiple participants. Existing choreography specification languages focus mostly on message sequences and are weak in modeling data shared by participants and used in sequence constraints. They also assume a fixed number of participants and make no distinction between participant type and participant instances. Artifact-centric business process models give equal considerations on modeling both data and control flow of activities. These models provide a solid foundation for choreography specification. This paper makes two contributions. First, we develop a choreography language with four new features: (1) Each participant type is an artifact schema with (a part of) its information model visible to choreography specification. (2) Participant instance level correlations are supported and cardinality constraints on such correlations can be explicitly defined. (3) Messages have data models, both message data and artifact data can be used in specifying choreography constraints. (4) The language is declarative based on a mixture of first order logic and a set of binary operators from DecSerFlow. Second, we develop a realization mechanism and show that a subclass of the choreography specified in our language can always be realized. The mechanism consists of a coordinator running with each artifact instance and a message protocol among participants.