Analysing normative contracts - On the semantic gap between natural and formal languages

Abstract

Normative contracts are documents written in natural language, such as English or Swedish, which describe the permissions, obligations, and prohibitions of two or more parties over a set of actions, including descriptions of the penalties which must be payed when the main norms are violated. We encounter such texts frequently in our daily lives in the form of privacy policies, software licenses, and service agreements. The length and dense linguistic style of such contracts often makes them difficult to follow for non-experts, and many people agree to these legally-binding documents without even reading them. By investigating the processing of normative texts, how they can be modelled formally using a suitable logic, and what kinds of properties can be automatically tested on our models, we hope to produce end-user tools which can take a natural language contract as input, highlight any potentially problematic clauses, and allow a user to easily ask questions about the implications of the contract, getting a meaningful answer in natural language within a reasonable amount of time. This thesis includes four research articles by the author which investigate the various components that a system such as this would require; from entity recognition and modality extraction on natural language texts, to controlled natural languages and visual diagrams as modelling interfaces, to logical formalisms which can be used for contract representation, to the different kinds of analysis possible and how this can be linked to user questions in natural language.