JML Support for Primitive Arbitrary Precision Numeric Types: Definition and Semantics

The Java Modeling Language, JML, is a notation for specifying and describing the detailed design and implementation of Java modules. It is a model-based specification language offering, in particular, method specification by preand post-condition, and class invariants to document required module behavior. It has recently been noted that the JML semantics of expressions over numeric types do not correspond to user expectations. As a result, an unusually high number of published JML specifications are invalid or inconsistent, including cases from the security critical area of smart card applications [Chalin03a]. In this extended abstract we briefly describe JML’s ancestry and language design principles (Section 2). This will help to explain the origin of the “semantic gap” between user expectations and the current meaning given to JML numeric expressions. With the objective of better matching user expectations, we introduce JMLa, a variant of JML supporting primitive arbitrary precision numeric types as well as implicit promotion to these types (Section 3). This is done in a manner that is consistent with JML’s language design goals and objectives [Chalin03a]. A preliminary formal semantics of JMLa expressions is given (Section 4) as well as an example of its application. Related and future work are described (Sections 5 and 6, respectively).