K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proc. of ECOOP, 2002.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....whereas virtual or abstract types are present in BETA [31] as well as more recently in gbeta [19] Rune [42] and Scala [33] An essential ingredient of these systems are objects with type members. There is currently much work that explores the uses of this concept in object oriented programming [38,40,20,36]. But its type theoretic foundations are just beginning to be investigated. As is the case for modules, dependent types are a promising candidate for a foundation of objects with type members. Dependent products can be used to represent functors in SML module systems as well as classes in object ....

K. Ostermann. Dynamically composable collaborations with delegation layers. In Malaga, Spain, 2002.

....resulting from using the JIT compiler and a modularized architecture. 1. INTRODUCTION Aspect Oriented Programming (AOP) 8] holds the promise of composing software out of orthogonal concern spaces [20] More recently, there has been a growing interest in using dynamic aspect oriented techniques [13, 11, 3, 16, 12] to express run time adaptations of services. In our research [18, 15] we have encountered a number of design problems that can be addressed by using dynamic AOP. A rst example is hot xes in web services. A hot x is an extension applied to a running application server to modify the behavior ....

K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proc. of ECOOP'2002.

....and their transient presence within the network boundaries. From a software engineering point of view, the question is how to design and implement a spontaneous container. A promising way to achieve this objective is to provide explicit programming support for dynamic adaptation models [42, 20, 27] and aspect orientation [9, 16] By exposing the aspect oriented run time support in such a system, one gains the ability to unify at a small cost the programming paradigms encountered in (i) containers and in (ii) spontaneous networks for mobile computing. Thus, a spontaneous container inherits ....

....than forcing the application to carry with it all the functionality necessary to interact with other applications or services, the computing environment of a spontaneous container should dynamically provide this functionality when needed. Dynamic adaptation New programming support infrastructures [27, 34, 8] allow changing applications at run time. This is the kind of property needed in a spontaneous container, where applications must be adapted on the y, as they join or leave a given computing environment. The nature of these adaptations (transactions, orthogonal persistence, security, logging) ....

K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proc. of ECOOP'2002), Malaga, Spain, 2002. Springer.

....than pre methods [1] Languages Work partly supported by DART, European Commission Research Directorates, IST 01 6 1A like SELF[6] allow an object to delegate execution of a method to another object. Delegation has recently been added as a feature to statically typed class based languages [11, 14, 15]. The dynamic features present in object based languages, such as method update and addition coupled with delegation give the ability to quickly react to changes in requirement even after execution has started, and thus support unanticipated evolution. We develop a succinct calculus, #, for such ....

....requirements for simulating delegation in Java using an API. Costanza and Kniesel [4, 10] added delegation to Java in a typesafe manner with the addition of a new keyword delegate. Viega [18] proposed adding delegation to Java in the context of allowing multiple inheritance. Ostermann [14] adds delegation and virtual inner classes to a simple class based language to allow the expression of a slice of behavior a#ecting a set of collaborating classes. With delegation we can represent a point by three objects. One object that knows how to print points, another how to move points, and ....

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Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of the 16th European Conference on Object-Oriented Programming (ECOOP), Malaga, Spain, 2002.

....roles, a technique very similar to family polymorphism. Type declarations may be of the form teamInstance.RoleClass. Determining the identity of two anchor instances in such declarations is simplified by requiring the anchors to be declared final, which has been suggested by Ostermann [15]. With respect to externalized role objects, i.e. role objects that are visible outside their Team, the modifier protected is redefined: following the intuition of a Team as a advanced package construct, protected methods are only accessible within the Team (instance) They are not accessibly ....

Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proc. of ECOOP 2002.

....roles, a technique very similar to family polymorphism. Type declarations may be of the form teamInstance.RoleClass. Determining the identity of two anchor instances in such declarations is simpli ed by requiring the anchors to be declared final, which has been suggested by Ostermann [15]. With respect to externalized role objects, i.e. role objects that are visible outside their Team, the modi er protected is rede ned: following the intuition of a Team as a advanced package construct, protected methods are only accessible within the Team (instance) They are not accessibly on ....

Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proc. of ECOOP 2002.

....to allow nesting of functions and function definitions as expressions. We want to extend the type system of BabyJ allow subtyping and parametric types. A promising route would add delegation to BabyJ, and consider whether to represent this in the translation to class based as delegation as in [13, 15] or through subclasses. Optimization of the translation from BabyJ to Java 0 in particular, when it can be shown that a functional member of an object is not re assigned, and therefore the case statement and int field in the translated code can be removed. We want to create tools to allow ....

Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of the 16th European Conference on Object-Oriented Programming (ECOOP), Malaga, Spain, 2002.

....layers [22] improve on this by using a layer of mixins to modularize a collaboration between many objects. Java Layers [4, 3] adds mixin layers to the Java language. The sibling class pattern [3] enabled by Java Layers provides the same functionality as Jiazzi s open packages. Delegation layers [21] improves on mixin layers by allowing new collaborations to be added at run time. MultiJava [5] adds direct support for open classes with an extension to the Java language. As in Jiazzi, open classes in MultiJava are fully supported with principled separate compilation. MultiJava open classes are ....

K. Ostermann. Dynamically composable collaborations with delegation layers. 2002.

....are present in BETA [MMPN93] as well as more recently in gbeta [Ern99] Rune [Tor02] and Scala [Ode02] An essential ingredient of these systems are objects with type members. There is currently much work that explores the uses of this concept in object oriented programming [SB98, TT99, Ern01, Ost02] But its type theoretic foundations are just beginning to be investigated. As is the case for modules, dependent types are a promising candidate for a foundation of objects with type members. Dependent products can be used to represent functors in SML module systems as well as classes in object ....

Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of the 16th European Conference on Object-Oriented Programming, Malaga, Spain, 2002.

....for modules that are larger than classes have emerged. Besides components as understood in the context of standard component models such as CCM and EJB, which are out of the scope of this paper, several other module proposals have been made for supporting the so called collaboration based design [5, 23, 19, 3, 20, 14, 4, 17]. Approaches of this kind build on the insight that the design of object oriented applications can be organized along two dimensions: structural abstractions (object types) and collaborations in which these abstractions are involved (see Fig. 1 for illustration) In general, an abstraction is ....

....of an example scenario, we illustrate the features that are needed and indicate what is missing in the current proposals for collaboration modules. We discuss only the three most advanced approaches to collaboration based design: mixin layers [20] family polymorphism [4] and delegation layers [17]. This can be done without loss of generality, since the chosen approaches essentially subsume the other approaches to collaboration based design. In response to the shortcomings that we identify, we propose a new kind of collaboration module, called Object Teams, which combines the best features ....

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K. Ostermann. Dynamically composable collaborations with delegation layers. In Proc. of ECOOP`02, LNCS. Springer--Verlag, 2002.

....emerged over the last decade. In addition to components as defined by standard component models such as the CORBA Component Model and Enterprise Java Beans, which are beyond the scope of this paper, several other module proposals have been made for supporting so called collaboration based design [4, 19, 16, 2, 17, 12, 3, 15]. Approaches of this kind build on the insight that the design of object oriented applications can be organized in two dimensions: using structural abstractions (object types) and collaborations in which these abstractions are involved (see Fig. 1) Generally speaking, an object is involved in ....

....ensure that each role always has a consistent base object. 2.3 Comparing proposals for collaboration modules The features presented so far roughly correspond to the capabilities of some approaches for composition and refinement of collaborations. A comprehensive discussion can be found in [15]. A comparison in terms of the major issues discussed so far is given in the table below. Object Teams fulfil all listed criteria. Object confinement is borrowed from the concept of family polymorphism [3] but Object Teams provide the option of more flexibility. While both approaches confine ....

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K. Ostermann. Dynamically composable collaborations with delegation layers. In Proc. of ECOOP 2002, LNCS. Springer Verlag, 2002.

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K. Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of ECOOP '02. LNCS 2374, pages 89--110. Springer, 2002.

....In addition, 10] and [8] rely on a dedicated mapping sublanguage that is less powerful than our object oriented wrappers with wrapper recycling. Finally, the lack of the notion of virtual types is another drawback of these approaches as compared to the work presented here. Delegation layers [13] are an approach to decompose a collaboration into layers and compose these layers dynamically at runtime. We plan to integrate delegation layers with Caesar in order to organize aspect implementations and bindings in layers and compose them dynamically. Caesar is also related to Hyper J and its ....

K. Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of ECOOP '02, LNCS 2374, Springer, 2002.

....CBD classes are decomposed into the roles they play in the di#erent collabo rations. The idea is nicely visualized by a two dimensional matrix with the classes as the column indexes and collaborations in which these classes are involved as the row indexes. Mixin Layers [26] and delegation layers [23] are two representatives of approaches to CBD. Both approaches provide concepts for composing and decomposing a collaboration into layers, such that a particular collaboration variant can be obtained by composing the required layers. Mixin layers use a nested variant of mixin inheritance [4] ....

....interfaces with generalized notions of inheritance and subtype polymorphism, provide for a high degree of reuse in our model. There are several areas of future work which were briefly outlined in the paper. First, we plan to combine our ap proach with concepts from the delegation layers approach [23]. This will allow us to decompose both components and connectors into layers that could be flexibly combined ondemand. Another very important area of future work is to extend our remodularization language with constructs for better supporting the integration of reusable crosscutting concerns, as ....

K. Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of ECOOP '02, LNCS 2374, Springer, 2002.

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K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proc. of ECOOP, 2002.

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K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In ECOOP, 2002.

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K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proceedings of the 16th European Conference on Object-Oriented Programming (ECOOP'02). Springer-Verlag, 2002.

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K. Ostermann. Dynamically Composable Collaborations with Delegation Layers. In Proc. of ECOOP'2002.

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Klaus Ostermann. Dynamically composable collaborations with delegation layers. In Proceedings of the 16th European volume 2374 of Lecture Notes in Computer Science, pages 89--110, M alaga, Spain, 2002. Springer-Verlag.

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K. Ostermann. Dynamically composable collaborations with delegation layers. In Malaga, Spain, 2002.

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