Coordination by Contract
Define terminology to be used
Identify parties to agreement
List all possible situations
Rights and obligations of each party
Define policies for each situation
When fulfilled, cancelled or violated
Contracts are statements of intent that regulate behavior amongst organizations and individuals, ranging from international trade law to verbal offer and acceptance between people. A contract is instantiated as a set of obligations between its parties, which are either fulfilled, cancelled or violated. A good contract defines the rights and obligations in every possible case, including violation. Just as a a contract has clauses that specify the courses of action in all situations, a contract diagram represents it through its deontic states and the conditions which relate them.
This is a specialization of a state transition diagram, where each state represents a particular situation, and the transitions represent the policies applicable in that situation, typically defined in a clause in the contract. Note that the contract does not describe a process, but the rights and obligations of each party, which govern the process. Not only does this have legal implications, it also enables an otherwise complex responsibilities to be clearly partitioned between the parties.