Automatic Addition of Conflicting Properties

The problem of model/program repair focuses on revising an existing model/program to satisfy new properties. These properties can be safety, liveness, availability, or fault-tolerance requirements. Existing solutions focus on adding compatible properties, i.e., properties that can be satisfied while preserving the existing properties. In other words, they try to generate programs that satisfy the existing properties as well as the new desired properties. It follows that if one were to add a conflicting property, i.e., a property that cannot be satisfied while preserving existing properties, then the previous solutions declare failure to obtain the desired program. However, adding conflicting properties arises when one replaces an existing requirement with another– e.g., replacing fairness requirement with priority to some process. In this paper, we focus on the problem of adding conflicting properties. We present an algorithm for explicit addition of properties that adds new desired properties while preserving only an explicitly specified subset of existing properties. In turn, we use it to develop an algorithm for adding conflicting properties. We illustrate our algorithms with an example of job scheduling.