Supporting Iterative Development of Robust Operation Contracts in UML Requirements Models

Developing adequate system operation contracts at the requirements level can be challenging. A specifier needs to ensure that a contract allows an operation to be invoked in different usage contexts without putting the system in an invalid state. Specifiers need usable rigorous analysis techniques that can help them develop more robust contracts, that is, contracts that are neither too restrictive nor too permissive. In this paper we describe an iterative approach to developing robust operation contracts. The approach supports rigorous robustness analysis of operation contracts against a set of scenarios that provide usage contexts for the operation. We illustrate the approach by developing a robust operation contract for a functional feature in a Location-aware Role-Based Access Control (LRBAC) model.