D. Kafura and K.H. Lee, "Inheritance in Actor Based Concurrent Object-Oriented Languages", ECOOP '89, pp. 131-145, Cabridge University Press, 1989.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....inherit the two behaviors separately, and to modify either to reflect changes in the concurrent program composition of a concurrent class. The second is the ability to make changes in the interaction behaviors of methods. The inheritance anomaly has been studied in great detail and many solutions [12, 23, 17, 22, 16] have been proposed. Most of these solutions are based on the separation of synchronization constraints from method implementations. Changes in interaction behavior of a method is achieved by changing the relevant synchronization constraints. Different instances of the inheritance anomaly do not ....

....In addition, CYES C supports many mechanisms to allow changes in the interaction behavior of methods. We give an example that illustrates the way in which the state partitioning anomaly can be resolved. The state partitioning anomaly occurs in the behavioral abstractionbased languages [12, 23, 14] when additions or modifications of methods in a subclass partition the states of objects of a superclass. Since the implementation of a method includes the state transitions that an object makes after the execution of the method, changes in the states (due to the state partitioning) therefore ....

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Dennis Kafura and Keung Lee. Inheritance in Actor based Concurrent Object-Oriented Languages. In Proceedings ECOOP'89, pages 131--145. Cambridge University Press, 1989.

....glance, objects and parallel programs seem to be a perfect match. However, this is not always the case. Problems with inheritance, encapsulation, and reusability are outstanding research issues for concurrent object oriented language designers since inheritance and synchronization often conflict [1] [2] This problem is caled the inheritance anomaly and requires the re definition of inherited methods to maintain the integrity of concurrent objects. Most parallel object based languages therefore either do not support inheritance [3] or do so by compromising the encapsulation [4] or the ....

D. Kafura and K.H. Lee, "Inheritance in Actor Based Concurrent Object-Oriented Languages", ECOOP '89, pp. 131-145, Cabridge University Press, 1989.

....policy into methods that access the message queue representation. This tight coupling often inhibits the reuse of the resource implementation by derived classes that require specialized or different synchronization policies. This problem is commonly referred to as the inheritance anomaly [7,8,9,10]. A more flexible implementation is to decouple the explicit synchronizationpolicy code from the methods that access and update the shared resource. This decoupling requires that the Client Interface be defined separately. It is used solely to cause the construction of a Method Object for each ....

D. G. Kafura and K. H. Lee, "Inheritance in Actor-Based Concurrent Object-Oriented Languages," in ECOOP'89 Conference Proceedings, pp. 131--145, Cambridge University Press, 1989.

....mechanisms can remain external to the Servant. Therefore, methods in the Message Queue Servant class do not include any code that implements synchronization or mutual exclusion. It only provides methods that implement the Servant s functionality. This design avoids the inheritance anomaly [10, 11, 12, 13] problem, which inhibits the reuse of Servant implementations by subclasses that require specialized or different synchronization policies. 2. Implement the Proxy and Method Requests: The Proxy provides clients with an interface to the Servant s methods. For each method invocation by a client, ....

D. G. Kafura and K. H. Lee, "Inheritance in Actor-Based Concurrent Object-Oriented Languages," in ECOOP'89 Conference Proceedings, pp. 131--145, Cambridge University Press, 1989.

....= cod= buffer[out buffer.size( out (out 1) when ( in out) buffer.size( full when (in out) 0 empty else partial) Fig. 7. Inheritance anomalies induced by Types f Example 7. Figure 7 illustrates an example of inheritance anomaly with respect to Types f in ACT [17]. ExtBu# inherits from Bu#er and adds new methods get rear (acceptable unless the object is empty) and get2 (which removes two elements and hence is acceptable if there are at least two elements) Each method specifies the next accept set by a become statement. In order to define ExtBu# in ACT ....

....method guards. concurrency and the functionality code. The proposals should also be compared with respect to e#ciency. language inheritance behaviour implementation inheritance anomaly mechanism preserving independent Types f Types R Types T internal CUBL [27] GUARDS Yes KEYS Yes No No ACT [17] ACCEPT SETS Yes No No No No Types f ROSETTE [30] ACCEPT SETS Yes No No No No Types f DEMETER [20] GUARDS Yes KEYS Yes LOC R LOC R Types f MAUDE [25] PATTERNS Yes No Yes No No Types f MAUDE [18] PATTERNS Yes No Yes LOC R LOC R Types f [ 26] GUARDS SETS Yes Yes Yes LOC R LOC R Types f [ 6 ] ....

D. G. Kafura and K. H. Lee. Inheritance in Actor based concurrent object-oriented languages. In ECOOP'89, pages 131--145, UK, 1989. Cambridge University Press. 589, 597

....for the methods of an object. For instance some methods may need to be executed in mu tual exclusion or may need to be ordered to ensure the coherence of some instance variables. This level is similar to the meta level of reflective languages and metaobject protocols (e.g. Open C [9] ACT [16], CLOS [6] or ABCL R [27] An object state is a mapping from the set of instance variables to a set of values. A transition between two object states is associated with a synchronized method. A group behavior factorizes several object behaviors. So the object model is a particular refinement of ....

D.G. Kafura and K.H. Lee. Inheritance in actor based concurrent object-oriented languages. The Computer Journal, 32(4):297--304, 1989.

....on the other side create new problems. For instance the so called inheritance anomaly [19] refers to the various limitations that arise in introducing inheritance in a concurrent programming language. This difficulty has been thoroughly studied and several solutions have been proposed [15, 25, 2, 13, 11]. Furthermore the non determinism introduced by a distributed environment where objects instantiated on remote sites may become temporally or permanently unreachable imposes to modify the semantics of method invocations. For instance the runtime system needs to guarantee whether a request is ....

D.G. Kafura and K.H. Lee. Inheritance in actor based concurrent object-oriented languages. In Proceedings of the 3rd European Conference on Object-Oriented Programming (ECOOP'89), pages 131--145. Cambridge University Press, July 1989.

....and persistence are examples of non functional issues. Combining inheritance with concurrency poses problems in that it is difficult to define classes that make use of concurrency mechanisms and can be then inherited and extended in any meaningful way without exposing implementation details [19] [27] That one would like to configure these non functional aspects independently from the functional issues can also seen from the fact that objects that function correctly in a sequential environment may fail when exposed to concurrent clients [46] Similarly, one would like to switch ....

Dennis G. Kafura and Keung Hae Lee, "Inheritance in Actor Based Concurrent Object-Oriented Languages," Proceedings ECOOP '89, ed. S. Cook, Cambridge University Press, Nottingham, July 10--14, 1989, pp. 131--145.

....group. Objects may be multithreaded. This level gives the synchronization policy for each object. For instance some methods may need to be executed in mutual exclusion or may need to be ordered to ensure the coherence of the instance variables. In some object languages (e.g. Open C [7] Act [10]) this level is often called the metalevel. The synchronization policy denes local knowledge predicates compatible with the group knowledge predicates. The local knowledge of an object is the set of instance variables managed and accessed by the methods of the object. A group behavior factorizes ....

D.G. Kafura and K.H. Lee. Inheritance in actor based concurrent object-oriented languages. The Computer Journal, 32(4):297304, 1989.

....we specify each object directly in details. The object level describes the behavior of a member object of the group. It gives the synchronization policy for the object methods. This level is similar to the meta level of reflective languages and meta object protocols (e.g. Open C [Chi95] Act [KL89] CLOS [BDB 88] or ABCL R [WY88, Yon90] The object level behavior is defined with a state transition automaton. As we need to consider intra object parallelism its semantics, that is presented in [SDF96] differs from the usual semantics of finite state automata theory. Finally the method ....

D.G. Kafura and K.H. Lee. Inheritance in actor based concurrent object-oriented languages. The Computer Journal, 32(4):297--304, 1989.

....A complete separation of synchronization code from algorithmic code is not realized. Inheriting from a class synchronized by Accept Sets is often a pain as lots of inheritance anomalies can occur. Implementations falling into the category of Accept Sets are the Behavioural Abstractions in ACT [6] and Tomlinson s Enabled Sets [9] The basic idea of Method Guards is that every method of an object has a guard controlling the invocations of this method. These guards are synchronization constraints, which must be fulfilled to allow invocations of the associated method. Method Guards make a ....

D. Kafura; K. Lee: "Inheritance in Actor Based Concurrent Object-Oriented Languages". ECOOP `89, Conference on Object-Oriented Programming, Cambridge University Press, Cambridge MA, 1989, pp. 131-145

....In a distributed environment, autonomous objects constantly interact to achieve coordination and information exchange. Messages may arrive at any given moment. A selection conflict occurs within a server entity when multiple conflicting requests are competing to be scheduled. Scheduling Controls [5,9] decide what should be done next among available choices, and hence support scheduling. Two forms of message race conflict are considered here. One, also known as the inter method race, is concerned with resolving conflicts among executable method entries inside an object. Since requests may ....

Kafura, D.G., and Lee, K.H., "Inheritance in ActorBased Concurrent Object-Oriented Languages," The Computer Journal, Vol. 32, No. 4, pp. 297304, 1989.

....related works Extensive studies [1,2,7,8,11,17] have been done in the area of providing linguistic supports for programmers to express synchronization requirements for object systems. Issues such as the difficulty in supporting reuse of synchronization constraint also has been widely examined [10,13,17,20]. However, these approaches tend to overlook the importance of making objects more responsive to its operating environment. Actor modelbased systems seem to provide a better alternative in assisting objects for intelligent request management. 7] presents a decision control mechanism that permits ....

Kafura, D.G., and Lee, K.H., "Inheritance in Actor-Based Concurrent Object-Oriented Languages," The Computer Journal, Vol. 32, No. 4, pp. 297-304, 1989.

....should be suitable for extension by subclasses. Although such a mechanism is not provided by most conventional methods, several object oriented languages provide a mechanism for specifying states. This is primarily useful for purposes of synchronization and concurrency control. Examples are ACT [55] and Rosette [71] However, there may be some situations where a certain extension of a class requires extensive redefinitions, whereas this seems intuitively unnecessary. We demonstrate an example of the so called State Partitioning Anomaly [62] which is exemplified by a class BoundedBuffer. The ....

D.G. Kafura & K.H. Lee, Inheritance in Actor Based Concurrent Object-Oriented Languages, ECOOP '89, pp. 131-145, 1989.

....was given to support for inheritance and the term inheritance anomaly, introduced by Matsuoka [MY93] has been widely adopted for referring to related problems. Although, several proposals were presented for overcoming the inheritance anomaly, AGMB91, Ber94, Car90, TS89, Fr92, HSB 96, KL89, KMV 90, McH95, MTY93] to name a few, they have focussed on a particular issue: the specification and reuse of message acceptance constraints. However, earlier research on the design of COOPLs and concurrent programming [Gen81, LH83, Nie87, YSTH87] has identified other issues that have to be ....

....for processing messages by using subordinate objects. Although modular concurrent programming languages and early COOPL have provided features that address the expressive power requirements, they have failed to address the software composition requirement. It has been identified[Ame87b, TS89, KL89] that their features conflict with objectoriented features that support software composition and inheritance more particularly. 2.2. Addressing Software Composition Based on Inheritance Object oriented languages provide different software composition techniques, such as inheritance, delegation ....

D. G. Kafura and K. H. Lee. Inheritance in actor based concurrent objectoriented languages. In S. Cook, editor, Proceedings of the Third European Conference on Object-Oriented programming Languages, British Computer Society Workshop Series. CAMBRIDGE UNIVERSITY PRESS, 1989.

....the new constraints; hence, inheritance is rendered useless. Recent work on the problem has demonstrated that the anomaly occurs across a spectrum of concurrent object oriented languages, regardless of the type of mechanism employed for specifying synchronization constraints [America 87, Briot 90, Kafura 89, Nierstrasz 87] A deeper issue is that the concurrent object oriented research community does not yet have a good semantic model that relates the type features and the concurrency features of concurrent object oriented languages. In the remainder of this paper, the inheritance synchronization ....

....Any instance of a class not derived from the Actor class is a passive object. Concurrency is achieved using the become operation that is implemented in the Actor class. The notion of behavior abstraction was originially proposed in ACT as a mechanism for capturing the behavior of an object [Kafura 89] Upon initial examination, behavior abstraction seems powerful since synchronization can be achieved naturally by dynamically modifying the visibility of the object interface using the become operation. The efficacy of this mechanism and its degree of interaction with the C inheritance ....

Dennis G. Kafura and Keung Hae Lee. "Inheritance in actor based concurrent objectoriented languages," ECOOP'89 Conference Proceedings, pp. 131-145, Cambridge University Press, 1989.

....inherit the two behaviors separately, and to modify either to reflect changes in the concurrent program composition of a concurrent class. The second is the ability to make changes in the interaction behaviors of methods. The inheritance anomaly has been studied in great detail and many solutions [4, 14, 8, 13] have been proposed. Most of these solutions are based on the separation of synchronization constraints from method implementations. Changes in interaction behavior of a method is achieved by changing the relevant synchronization constraints. Different instances of the inheritance anomaly do not ....

....In addition, CYES C supports many mechanisms to allow changes in the interaction behavior of methods. We give an example that illustrates the way in which the state partitioning anomaly can be resolved. The state partitioning anomaly occurs in the behavioral abstraction based languages [4, 14, 6] when additions or modifications of methods in a subclass partition the states of objects of a superclass. Example 0.3. State partitioning) Let queueone be a subclass of queue. It defines a method gettwo. Method gettwo accesses two elements of the queue object atomically. Invocations of gettwo ....

Dennis Kafura and Keung Lee. Inheritance in Actor based Concurrent Object-Oriented Languages. In Proceedings ECOOP'89, pages 131--145. Cambridge University Press, 1989.

....CCR 9104013. 2 Our goal in designing ACT was to provide the ability to specify and control concurrent objects in C . Instead of inventing a new model of concurrent computation we decided to implement some features of the Actor model of concurrent computation [Agha 86, Agha and Hewitt 87] [Kafura and Lee 90] describes the design issues and the implementation details of an earlier version of ACT . This paper describes ACT 2.0, the latest version which enhances the earlier one in three respects. First, we have used the PRESTO [Bershad et al. 88, Bershad 90] threads package as the underlying system to ....

....system to control concurrent objects. PRESTO was used because it is written in C and provides a high level abstraction for concurrent programming using light weight processes called threads. Second, we have implemented a concurrency control mechanism called behavior sets [Lavender and Kafura 90] which can be used to resolve the conflict between the inheritance mechanism of object oriented languages and the specification of synchronization constraints. Third, we have introduced special features using which simultaneous input output requests from multiple, simultaneously executing threads ....

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Kafura, D., and Lee, K.H., "Inheritance in Actor Based Concurrent Object-Oriented Languages," ECOOP '89 Proceedings.

....to an object can be computed and controlled based on the internal state of an object. Various techniques have been proposed in different language contexts. Tomlinson and Singh implemented Enabled Sets in Rosette [Tomlinson 1989] while Kafura and Lee implemented Behavior Abstraction in ACT [Kafura 1989]. Protocol machines have similar requirements for synchronization control. By incorporating both the downcall and upcall methods in the class interface, rather than separating them, OOSI is in a position to exploit future developments with regard to controlling method access via an object ....

Dennis G. Kafura and Keung Hae Lee. "Inheritance in actor-based concurrent object-oriented languages," ECOOP'89 Conference Proceedings, Cambridge University Press, 1989, pp. 131---145.

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D. Kafura and K. H. Lee. #Inheritance in actor based concurrent object-oriented languages," ECOOP'89 Conference Proceedings, pp. 131#145, Cambridge University Press, 1989. 42

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D. Kafura and K.H. Lee, "Inheritance in Actor Based Concurrent Object-Oriented Languages", ECOOP '89, pp. 131-145, Cabridge University Press, 1989.

No context found.

D. G. Kafura and K. H. Lee. Inheritance in actor-based concurrent object-oriented languages. In S. Cook, editor, Proceedings of ECOOP'89, Nottingham, UK, pages 131--145. Cambridge University Press, 1989.

No context found.

Dennis Kafura and Keung Lee. Inheritance in Actor based Concurrent ObjectOriented Languages. In Proceedings ECOOP'89, pages 131--145. Cambridge University Press, 1989.

No context found.

Dennis Kafura and Keung Lee, Inheritance in Actor Based Concurrent Object-Oriented Languages, Proc. ECOOP'89, Cambridge University Press, pp. 131#145 (1989).

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D. Kafura and K. Lee, "Inheritance in Actor Based Concurrent Object-Oriented Languages", ECOOP 89 Proceedings of the Third European Conference on Object-Oriented Programming, 1989, pp. 131-145.

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