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...one level of abstraction are shielded fromsimplementation details at lower levels of abstraction.sLiskov goes as far as to suggest that "for abstraction to work, implementations must besencapsulated" =-=[53]-=-. In practice, this means that each class must have two parts: an interfacesand an implementation. The interface of a class captures only its outside view, encompassingsour abstraction of the behavior...

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...e triggers non-deterministically. In some cases, however, the user may want to have more control over trigger-firing. This approach is common in many programming languages, such as Eiffel [78] or C++ =-=[97]-=-, where the programmer has to resolve inheritance conflicts explicitly. User-defined inheritance can be expressed in F-logic as follows. To resolve a conflict, say, in a binary method, mthd, we can fi...

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... standard protocol results automatically. Thus, class inheritance not only supports software reuse by programming-by-difference, it also helps develop standard protocols. Another benefit of class inheritance is that it allows extensions to be made to a class while leaving the original code intact. Thus, changes made by one programmer are less likely to affect another. The code in the subclass defines the differences between the classes, acting as a history of the editing operations. Not all object-oriented programming languages allow protocol and inheritance to be separated. Languages like C++[Str86] that use classes as types require that an object have the right superclass to receive a message, not just that it have the right protocol. Of course, languages with multiple inheritance can solve this problem by associating a superclass with every protocol. 2.4 Abstract Classes Standard protocols are often represented by abstract classes [GR83]. An abstract class never has instances, only its subclasses have instances. The roots of class hierarchies are usually abstract classes, while the leaf classes are never abstract. Abstract classes usually do not define any instance variables. However, ...

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...ng Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. c fl 1994 ACM xxxx-xxxx/xx/xxxx-xxxx $xx.xx 2 \Delta B. Liskov and J. Wing Myrhaug, and Nygaard 1970], C++[=-=Stroustrup 1986-=-], Modula-3[Nelson 1991], and Trellis/Owl[Schaffert, Cooper, Bullis, Kilian, and Wilpolt 1986], subtypes are used to broaden the assignment statement. An assignment x: T := E is legal provided the typ...

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...ical requirements. All eight projects were developed using a sequential life cycle model, a well-known Object-Oriented analysis/design method [Rumbaugh et al, 1991], and the C++ programming language [=-=Stroustrup, 1991-=-]. In fact, we used an experiment framework that should be representative of currently used technology in industrial settings. This study discusses the strengths and weaknesses of the validated OO met...

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...ence arcs are annotated with the value zero. Computation and display of the reflexion model shown in Figure 2 takes twenty seconds on a DEC 3000/300 with our tools, which consist of several small C++ =-=[Str86]-=- programs and a user interface implemented in TCL/TK [Ous94]. Computed reflexion models are displayed using AT&T's graphviz package. The tools allow the engineer to select arcs in a reflexion model, p...

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...ynchronized programs (e.g., allow the behavior shown in Figure 2), or they do not allow dependencebreaking transformations as shown in Figures 5 and 6. In programming languages such as C [23] and C++ =-=[41]-=-, threads are not part of the language specification. Instead, libraries such as POSIX threads (pthreads) [27] support multi-threading. Since the C/C++ spec doesn’t talk about threads and the pthreads...

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... each statement in the source program into a sequence of binary instructions. Over time a series of system programming languages evolved from Algol, including such languages as PL/1, Pascal, C[4], C++=-=[9]-=-, and Java[1]. System programming languages allow applications to be developed much more quickly than assembly languages while providing nearly the same level of efficiency. As a result, they have alm...

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...hilosophy of Charm is discussed in Section 3, along with the guiding principles that we used for synthesizing these parallel programming constructs with object oriented constructs. We chose to use C++=-=[27]-=- as the underlying language, although the basic parallel constructs are equally applicable in other object oriented languages as well. Section 4 describes the resultant language, including the structu...