Programming Contract Amending

Legal contracts can be generally amended either because real-world events require an adaptation of the contract to new circumstances or because new agreements between the parties take place. When legal contracts are defined by a programming language, amendments likely entail runtime modifications to the contract code. In this paper, we present a law-derived framework for amending contract codes that are written in Stipula, a programming language for legal contracts. The full language, called higher-order Stipula, is applied to modelling real-world examples of contract amendments, where modifications may add new clauses or may rewrite (part of) old ones. We also discuss the prototype implementation of the language and its graphical user interface.