Encapsulation in Object-Oriented Programs

In stead of decomposing data and procedures, object-oriented (OO) programming encapsulates the both through an object. An object is instantiated from a class which defines attributes (related data) and methods (operational procedures). The definition of a class may be recursive since the class can encapsulate he instance(s) of another classes as its attributes. An object containing other objects is called a complex object. The form of a most primitive object, an object containing no other object, is nothing but a data entity and is called a simple object. Encapsulation solidates an object by hiding the details; it may also obstruct dependency analysis for complex objects by information hiding. Program Dependency Graph (PDG) [OtOt84] represents he structure of a program. It is a set of graphic representations, vertices for entities in a program and edges for dependencies between the entities. PDG has been used in various dependency analysis techniques, such as program slicing [HoRe+91] and program optimization [FeOt+87]. Recently, many researches (such as [MaMc+94, LaHa95, ZhCh+96]) extended PDG, by augmenting class and object relationships (e.g., inheritance, membership,..., etc.) in a PDG, to represent OO programs for dependency analysis. In extended PDG's, a vertex denotes an object while an edge denotes a dependent relation. However, a complex object can not guarantee the cohesion of and coupling among its components o be strong. Extended PDG's hav