Representing and Enforcing E-Commerce Contracts Using Occurrences

This paper describes an approach for representing electronic commerce contracts using occurrences. We first define what is meant by an occurrence and demonstrate how an occurrence may be used to store a workflow event, such as a purchase. Next we demonstrate how the occurrence abstraction can be used to store names. We continue with an explanation of various types of query and demonstrate how queries can be represented and stored using occurrences. We show that the storage of queries is necessary in order to determine which stored descriptions describe a given occurrence, and consequently which policies apply to that occurrence. A discussion of contracts and their representational requirements follows, and we show how occurrences and queries may be used to represent defined terminology, regular and conditional duties, permissions, and powers in contracts. We provide an overview of our implementation and describe related work.