| Object types are abstract specifications of object behaviors; object behaviors are abstractly indicated by object component interdependencies; and program verifications are based on object behaviors. In conventional object type systems, object component interdependencies are not taken into account. As a result, distinct behaviors of objects are confused in conventional object type systems, which can lead to fundamental typing/subtyping loopholes and program verification troubles. In this paper, we first identify a program verification problem which is caused by the loose conventional object typing/subtyping which is in turn caused by the overlooking of object component interdependencies. Then, as a new object typing scheme, we introduce object type graphs (OTG) in which object component interdependencies are integrated into object types. Finally, we show how the problem existing in conventional object type systems can be easily resolved under OTG. |
