Logic-Based Tools for the Analysis and Representation of Legal Contracts

There has been a significant amount of research in Artificial Intelligence focusing on the representation of legislation and regulations. The motivation for this has been twofold: on the one hand there have been opportunities for developing advisory systems for legal practitioners; on the other hand the law is a complex domain in which diverse modes of reasoning are employed, offering ample opportunity to test existing Artificial Intelligence techniques as well as to develop new ones. The general aim of the thesis is to explore the potential for developing logic-based tools for the analysis and representation of legal contracts, by considering the following two questions: (a) To what extent can techniques developed for the representation of legislation and regulations be transferred and applied usefully in the domain of legal contracts? (b) What features are specific to legal contracts and what techniques can be developed to address them? The intended applications include both the drafting of new contracts and the management and administration of existing ones, that is to say, the general problem of storing and retrieving information from large contractual documents, and more specific tasks such as monitoring compliance or establishing parties’ duties/rights under a given agreement when it is in force. Experimental material is drawn mostly from engineering contracts, which are typically large and complex and contain a multitude of interrelated provisions. The term ‘contract’ is commonly used to refer both to a legally binding agreement between (usually) two parties and to the document, that records such an agreement. The first part of the thesis is concerned with documents and the representation of contracts at the macro-level: the emphasis is on issues relevant to the design of structurally coherent documents. The thesis presents a document assembly tool designed to be applicable, where contract drafting is based on model-form contracts or existing examples of a given type. The main features of the approach are: (i) the representation addresses the structure and interrelationships between the constituent parts of contracts but not the text of the document itself; (ii) the representation of documents is separated from the mechanisms that manipulate it; and (iii) the drafting process is subject to a collection of explicitly represented constraints that govern the structure of documents. The second part of the thesis deals with the contents of agreements and representations at the micro-level. Micro-level drafting is the source of a host of issues ranging from representing the detailed wording of individual sections, to representing the nature of provisions (obligations, powers, reparations, procedures), to representing their "fitness" or effectiveness in securing some party's best interests. Various techniques are available to assist in aspects of this task, such as disambiguating contractual provisions and in detecting inconsistency or incompleteness. The second part of the thesis comprises three discussions. The first is on contractual obligations as the result of promissory exchanges between parties and draws upon work by Kimbrough and his associates. The second concentrates on contractual obligations and common patterns encountered in contracts. The third is concerned with temporal verification of contracts and shows how the techniques employed in model checking for hardware specification can be transferred to the domain of contracts.