Figure 1 Contract ontology adopted from Symboleo [9] using standard UML notation for class diagrams. An ontology consists of a collection of concepts and relationships for conceptualizing a domain, in our case contracts. The ontology we adopt has been proposed in [9] for the Symboleo contract specification language and is shown in Figure 1. The ontology is based on the Core Legal Ontology UFO-L [10] and was developed in consultation with legal experts incorporating Hohfeld’s theory of legal positions [11] but without some of its shortcomings to address contract specific elements. In addition, it has been tested with dozens of contracts to confirm with legal experts its ability to capture legal discourse and its implementation is available to the public. Contract: a collection of obligations and powers between two or more roles, which are assigned to parties during contract execution, and are concerned with two or more assets respectively associated with each role. Contracts may involve subcontracting that assigns to third parties the responsibility for the fulfilment of obligations.