L. Stein. Delegation is inheritance. In Proc. of the ACM Conf on Object-Oriented Programming Systems and Languages (OOPSLA), 1987. 16  Home/Search   Document Not in Database   Summary   Related Articles   Check

....of behaviour and a run time entity: it specifies responses to incoming messages and has the responsibility to generate new instances of that class. Inheritance can be viewed as the delegation to another class, the super class, of all messages for which the class has no specified response [8]. Object. An object is an instance of a class. It has a modifiable state consisting of a set of acquaintances references to other objects or classes and it communicates with other objects by call reply exchanges. Objects may or may not execute concurrently. 3. Events and Sensors The ....

L.A.Stein, "Delegation is Inheritance", ACM SIGPLAN Notices, Proceedings OOPSLA 87, vol. 22, no. 12, pp. 138-146, Dec 1987.

....entities without class or inheritance mechanism. They draw closer to prototypes [11] if we note that each activity initiator can be considered as the kMS which acts as the default delegate. So, at run time, contexts use the usual inheritance mechanism, through the layout of the delegates [16]. Strictly speaking, this point implies that we must have capabilities to alter the environment of the activity since we want our approach to modify an X Y cont a cont b cont c pref 1 pref 2 pref 3 pref 4 X Y XY Z attr a attr b activity B context of activity B context of ....

Stein L.A. Delegation is inheritance. OOPSLA, 1987.

....5. mapping generalisation patterns in modelling and programming languages The left hand side of figure 5 shows the most common generalisation pattern in modelling languages and on the right hand side is one of the generalisation patterns found in programming languages and is the delegation model [7,8]. Element3 delegates to element2, this is achieved through the uses and implements relation. The delegationInheritanceMap template maps these two patterns. Again, in addition to the classes and association, well formedness rules expressed as OCL constraints are used to express properties and ....

L. Stein. Delegation Is Inheritance. OOPSLA ,87 Conference Proceedings.

....instances and their classes and subclasses and their superclasses thus introduces inflexibility in distributing programs. The family of delegation based languages often also prototype based introduces an alternative concept to provide object orientation which is of equal expressive power ( Ste87] as class based languages. Here, objects are created by cloning an existing object instead of instantiating from a class. Inheritance is implemented by delegating messages unknown to a an object to a parent object. By keeping state separated from behavior, the instance class relation is ....

Lynn Andrea Stein. Delegation is inheritance. ACM SIGPLAN Notices, 22(12):138-- 146, December 1987.

....directly, rather than modifying classes producing indirect effect on objects, and thus any object can be given individualized local behavior. Conceptual economy and elegance are achieved over classes with a small number of instances [Weg87] and sharing of information can be determined dynamically [Ste87]. The drawbacks include difficulties in modifying objects per group [Weg87] and unnatural representation of some concepts (for example what is a prototypical integer ) Tai93] 4.5.4 Mechanism vs. concept Prototype based inheritance is more a mechanism that provides means for sharing and ....

Stein, L.A., Delegation is Inheritance. In Proceedings of OOPSLA'87 (Orlando, Florida, October 4-8). ACM SIGPLAN Notices, Vol.22, No. 12 (Dec) 1987. pp.138-146.

....with the one achieved by delegation in prototype based languages. We also point out that there are two possible semantics for delegation links. 1 Introduction Prototype based languages are traditionally opposed to class based ones and many comparisons between them have already been proposed [4, 15, 12, 11]. More specifically the delegation mechanism, which is part of many prototype based languages [1, 8] has been compared to the class inheritance mechanism appearing in class based languages. Both mechanisms are inheritance mechanisms and achieve some kind of sharing. The one achieved by delegation ....

....[8] Lieberman claims that delegation is more powerfull than class inheritance since he can simulate the latter using the former but not map the reverse. On the counterpart, Stein states that delegation is class inheritance by presenting a model for class inheritance which also captures delegation [12]. However, these two simulations are based on a certain use of language entities which is not natural: simulating class inheritance using delegation expects some prototypes to act as classes, and the reverse simulation expects classes to be considered as instances. The key point is that there is ....

L.A. Stein. Delegation is Inheritance. In Proceedings of 2nd OOPSLA, Orlando, FL, ACM SIGPLAN Notices (22)12 , pp. 138--146, 1987.

....the definition of object oriented. The literature exposes an innumerable work on the semantics of the inheritance mechanism[Car84, CW85, CP89] on its use [HO87] on multiple inheritance problems [CG90, DHHM92, DHHM94] on new model of inheritance [BC90, JA92] and on alternative solutions [Lie86, Ste87] Inheritance is a mechanism for incremental programming, but two points of view face: on the one hand, one associates inheritance subtyping properties, one the other hand, inheritance is distinguished from subtyping [Ame90, LP91] In all this paper, we do not connect inheritance with any ....

Lynn Andrea Stein. Delegation is Inheritance. In Proceedings of OOPSLA'87, pages 138--146, October 1987.

....according to Wegner[35] intrinsic to the definition of object oriented. The literature has innumerable works on the semantics of the inheritance mechanism[4, 5, 9] on its use [21] on multiple inheritance problems [6, 16, 17] on new models of inheritance [2, 24] and on alternative solutions [27, 34]. We consider inheritance as a mechanism for incremental programming. The idea presented in this paper is to investigate the inheritance mechanism as a relational information between classes and to express it in a distinct way from class structure and functionalities. In this sense, we reject ....

L. A. Stein. Delegation is Inheritance. In Proceedings of OOPSLA'87, pages 138--146, October 1987.

.... semantics [Stro86] Other languages simply avoid multiple inheritance by claiming it isn t really needed or by advocating other concepts such as protocols [Next93] A plethora of papers have been published debating the merits of multiple inheritance and proposing alternative semantics for it [Stei87][Pede89] Brac90] Carr90] Mili90] Duco92] The Idol programming language advocates a simpler inheritance model in which multiple inheritance, including directed acyclic graphs (DAGs) and even cyclic inheritance relationships, are simple and easily interpreted by humans and software tools [Jeff90] ....

Stein, L. A. Delegation is Inheritance. In Meyrowitz, N., editor, Proceedings of the Second ACM Conference on Object-Oriented Programming Systems, Languages and Applications, volume 22, pages 138--146, Orlando, FL, October 1987.

....for a method in its superclasses. The idea of this message dispatching for the methods defined along the inheritance hierarchy (or is a hierarchy) is still applied to each object, and each role, in DOOR. Indeed, in DOOR, this method lookup scheme is augmented with a similar idea called delegation [16] along the played by relationship of the roles being played by an object. Two method lookup modes are supported: Upward lookup: the method is looked up first in the receiving role and then in its ancestor players. Double lookup: the method is first looked up in the receiving role, and then in ....

L.A. Stein. Delegation is Inheritance. In OOPSLA '87 Proceedings, October 1987.

....With respect to our criteria, Concurrent Aggregates satisfy the program modeling criteria reasonably well. Arbitrary types (aggregates) may be defined, as well as arbitrary relationships between types. Delegation is supported which is equivalent in expressive power to inheritance [Ste87] The model even expresses continuations and messages as first class objects. Unfortunately, CA makes a distinction between an object defined outside of a CA and a representative of a CA. This is because the structure of the objects stored in a CA is part of the CA itself. This is a similar ....

Lynn Andrea Stein. Delegation is Inheritance. In OOPSLA '87 Proceedings, pages 138--146, Orlando, FL, October 1987.

....in Java, since the language accepts only multiple inheritance of interfaces, but not of classes. The interface delegation technique uses a combination of delegation and interface conformance. Delegation is used to simulate the form of parent class reuse (Rumbaugh et al. 1991) In delegation (Stein 1987), an object uses a specialized class that is embedded in itself to perform special operations. In this case, the object is composed of other objects, which it uses to perform the methods that it should have inherit, but did not because of the absence of a multiple inheritance implementation. ....

L. Stein (1987) Delegation is Inheritance. in: OOPSLA'87, Orlando, FL, pp 138-146.

....of class de nitions (as well as other run time modi cations of 2 the class hierarchy) Thus the complete class hierarchies are not known at compile time or at any stage preceding the actual program execution. CLOS [20] and Smalltalk are two such languages. Additionally, prototype based languages [3, 5, 33] are also examples of such languages. Name resolution in presence of late binding is easily solved for static object oriented languages (such as Java and C ) since the complete class hierarchy is known at compile time; simple table lookups allow for constant time name resolution. For dynamic ....

....for a given call. This determination may now, however, involve search of the class hierarchy at runtime. How to eciently perform this search is the problem we address and analyze in this paper. Similar situations occur (with greater frequency) in prototype based object oriented languages [3, 5, 33]. In these frameworks the concept of class is not present, rather, it is replaced by the idea of prototypes. Objects and prototypes are created on the y and each object prototype can be cloned to create new objects; parent attributes are used to connect the objects into hierarchies; execution of ....

L. Stein. Delegation is Inheritance. In OOPSLA. ACM, 1987.

....objects which have the combined advantages of the original objects; Chapter 2. Supporting the needs of CSCW applications 20 . to make run time decisions, about the patterns of communication (and delegation) Delegation provides at least the same advantages as inheritance for CSCW. Indeed, Stein [Stein, 1987] has shown how inheritance is only a restricted form of delegation. The trade off that is made is space versus time. Delegation can be very slow without careful modelling whereas inheritance takes up a lot more space in sheer object size and is less flexible. In meeting the needs of CSCW ....

Stein, L.A. (1987): "Delegation is Inheritance." in Proceedings of OOSPLA'87, 1987, vol.October 4-8, pp.138-146.

....and different implementation of their operations. For example, some software units used in a C program may contain YACC code instead of plain C code, and some software units may be library functions that do not have implementation parts. We use the delegation model [Lieberman 86] Ungar 87] Stein 87] Orlando 89] instead of the more conventional class inheritance model to describe the sharing of behavior between software units. Delegation can simulate the class inheritance mechanism while supporting the sharing of attributes between individual objects. With the delegation mechanism, we ....

Lynn Andrea Stein, "Delegation is Inheritance, " in ACM OOPSLA `87, pp. 138-146, October 1987.

.... Composition vs Subclassing: Introducing the Problem Often, object oriented programmers use inheritance (a subclassing mechanism) as a code sharing technique rather than in recognition of an actual subclassing relationship between classes (Meyer [84] often uses inheritance in this way and Stein [104] argues that delegation is inheritance) This is problematic in all areas of object oriented development. The following vector example illustrates the problem from two different points of view. A vector Class Two different views are as follows: ffl Subclassing A vector can be defined to be ....

L. A. Stein. Delegation is inheritance. In Object Oriented Programming Languages Systems and Applications (OOPSLA 87), 1987. BIBLIOGRAPHY 259

....The specification also states that printing an empty buffer is a no op rather than an error. By writing the specification, or at least parts of it, before starting the implementation, one can benefit from the commonly advocated advantages of a structured development process [22] Cliff Jones [13] argues that formalism employed to justify early data structure and design decisions which helps avoid the most costly errors is the most important application of formal methods. Specifications written after the implementation tend to lay down irrelevant details of the specific implementation and ....

....ariane. IEEE Computer, pages 129 130, January 1997. 12] Craig A. Damon, Somesh Jha, and Daniel Jackson. Checking relational specifications with binary decision diagrams. In Proc. Foundations of Software Engineering 96, 1996. http: www.cs.cmu.edu afs cs.cmu.edu project nitpick www home.html. [13] Cliff B. Jones. A rigorous approach to formal methods. IEEE Computer, pages 20 21, April 1996. 14] Gregor Kiczales. Why are black boxes so hard to reuse. In Proceeding of OOPSLA 94, 1994. http: www.parc.xerox.com spl projects oi towardstalk transcript.html. 15] W. Kozaczynski and J. O. ....

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Stein, L.A.: Delegation is Inheritance. In Proc. OOPSLA'87, October 1987.

....from another. Many authors feel that delegationbased inheritance is also a better conceptual model of inheritance than class based inheritance, and is more powerful, as in class based inheritance only class objects can delegate methods and ordinary objects cannot delegate methods to other objects [Stein 87] Delegation also eliminates the potential infinite meta class regress in languages such as Smalltalk [Ungar 87] a x y Figure 3.6: The object a before the use of delegation. 49 Delegation based inheritance can also naturally allow an object to radically change its behaviour ( dynamic ....

....code reuse mechanism is based on delegationbased inheritance (Lieberman 86) Delegation based inheritance is more flexible than class based inheritance, because it allows any object to delegate a method to any other object. In classbased languages only class objects can delegate methods (Stein 87) Delegation based inheritance is also a better conceptual model of implementation inheritance, and it allows a single code reuse mechanism to be designed, based on the concept of method redirection, supporting both part of and inherits from object relationships. In APOSTLE, an object ....

L. A. Stein, "Delegation Is Inheritance", Proc. of the Conf. on ObjectOriented Programming, Systems, Languages and Applications, Orlando, Florida, 4-8 October 1987, pp. 138-146.

.... Delegation is the foundation of a number of objectoriented languages without classes, such as ThingLab [Bor81] Act 1 [Lie87] a Smalltalk without classes [LTP86] and, perhaps most notably, Self [US87] Such languages were shown to be equally as powerful conceptually as inheritance by Lynn Stein [Ste87], although she notes that, in practice, either delegation or inheritance may be more desirable. She even proposes a hybrid model that would allow for both delegation and inheritance in the same language. An excellent analysis of the similarities and differences in both sharing mechanisms is ....

L. Stein. Delegation Is Inheritance. In OOPSLA '87 Conference Proceedings. ACM SIGPLAN Notices 22, 12 (Oct. 1987).

....particular product model is a specialization of a more general lift model, a particular lift configuration is a specialization of a product model. 8 3. 2 Prototype Object Model As the previous section shows, we represent product models and configurations with a prototype based object model [9] [15]. Prototype model has some interesting properties, especially for engineering data modeling (see [2] 3] 5] We do not know any study trying to elaborate the prototype model to support the creation and long term maintenance of complex product models discussed in this paper. Some properties of ....

Lynn Andrea Stein. Delegation is inheritance. In Conference on Object-Oriented Programming Systems and Languages (OOPSLA), pages 138--146, 1987.

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L. Stein. Delegation is inheritance. In Proc. of the ACM Conf on Object-Oriented Programming Systems and Languages (OOPSLA), 1987. 16

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Lynn A. Stein. Delegation is inheritance. In Proc. OOPSLA'87, pages 138--146, 1987. 252

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L.A. Stein. Delegation is Inheritance. Proceedings of OOPSLA'87, ACM Sigplan Notices, 22(12):138-146, December 1987.

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Stein, L. A.: Delegation is Inheritance. In: Proceedings of the Conference on Object Oriented Programming Systems, Languages, and Applications, Orlando, Florida, October, 1987, pp. 138-146

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Lynn Andrea Stein, "Delegation is Inheritance," in ACM OOPSLA '87, pp. 138-146, October 1987.

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