The Contract Expression Language – CEL

This paper describes the Contract Expression Language (CEL), currently being developed at the industry consortium Content Reference Forum. The CEL is an XMLbased language designed to express contractual agreements between different parties for the purposes of capturing and communicating contractual information, and facilitating contract execution and enforcement by machines with respect to granted permissions, mandated obligations and stipulated prohibitions. In addition to modeling contractual agreements using the deontic concepts of rights, obligations and prohibitions, it has distinct features for specifying statements of intentional, factual and exclusive types, defining preference rules for resolving conflicts, and supporting lifecycles and trust management of contracts in open and distributed environments. This paper presents an overview of the CEL in terms of its data model, expressiveness and processing models, and illustrates its application in the Content Reference Framework for content distribution, and its compliance to the Business Collaboration Framework for ebusiness transactions.