The Evolution of Interoperability

This note is a retrospective review of our 2006 paper [1] on the properties of protocols, especially interoperability. A bit of history is in order. By 2006, the importance of a social semantics for protocols was well-established in the multiagent systems community. Further, commitments had emerged as the preeminent abstraction for capturing the semantics. The big advantage was that specifying the meaning of protocol messages in terms of the commitments among agents enabled the agents to act flexibly. Informally, the notion of flexibility derives from reasoning about the legal executions from a global perspective: if the set of legal executions of a protocol is a subset of those of another, then the latter is more flexible. For example, all other things being equal, a protocol that enables merchants and customers to exchange goods and payment in any order is more flexible than one that only supports payment before goods. Specifying protocols in terms of commitments promotes flexibility because compliance with a protocol amounts to fulfilling one’s commitments. This in principle frees a protocol designer from the necessity of specifying the order of messages. Flexibility is great! It ties in well with qualities that are commonly ascribed to agents—proactivity, opportunism, intelligent exception-handling, and so on. Flexibility is good from the business perspective. The greater the flexibility one can act with the greater are the opportunities for engaging others in business. For example, by adopting a protocol that enables payment and goods to be exchanged in any mutual order, a merchant can also engage customers who are unwilling to make their payments before the delivery of goods.