Extracting frame conditions from operation contracts

In behavioral modeling, operation contracts defined by pre- and postconditions describe the effects on model properties (i.e., model elements such as attributes, links, etc.) that are enforced by an operation. However, it is usually omitted which model properties should not be modified. Defining so-called frame conditions can fill this gap. But, thus far, these have to be defined manually - a time-consuming task. In this work, we propose a methodology which aims to support the modeler in the definition of the frame conditions by extracting suggestions based on an automatic analysis of operation contracts provided in OCL. More precisely, the proposed approach performs a structural analysis of pre- and postconditions together with invariants in order to categorize which class and object properties are clearly “variable” or “unaffected” - and which are “ambiguous”, i.e. indeed require a more thorough inspection. The developed concepts are implemented as a prototype and evaluated by means of several example models known from the literature.