Morven Gentleman. Message passing between sequential processes: the reply primitive and the administrator concept. Software|Practice and Experience, 11(5), 1981.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....statement causes the target of the contained expression to return its result to the original caller (i.e. of the operation containing the forward statement) rather than to the forwarding object. This is useful for administrator objects whose function is to allocate jobs to worker objects [Gent81]: forward ( worker.operation(job) After the job is forwarded, the worker will return directly to the original caller, and the administrator is immediately free to handle other requests. The coblock and coloop constructs generate a scope within which concurrent subactivities may be created. ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept", Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....when an event (i.e. the arrival of a message) takes place. Most of the work on actors has come from MIT though there are others who have adopted the paradigm. Message passing is also present in non actor systems such as Smalltalk and Thoth (see the Gentleman paper) See also Actor languages . [Agha85 Agha86 Bake78 Ferb83 Gent81 Hewi77a Hewi77b Jong86 Zimm84] OIS: Some object oriented modelling of o#ce information systems. Gibb82 Gibb84 Woo85b Woo86] Reliability: Various papers on aspects of reliability, resilience, recovery and fault tolerance. Haer83 Kohl81 Oki83 Shin84 Svob84 Verh78] Security: Security issues for objects seem to be ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept", Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....and how easily independent, message passing objects can be mapped to an actor world. Since message passing is the only medium for communication, it is also a natural step to map actors, and therefore objects, onto a heterogeneous environment of di#erent processors connected through a network. See [8] for a discussion of similar issues in an environment that supports synchronous message passing. 8 Concluding remarks. The fundamental concepts in an object oriented environment are data abstraction and inheritance. A programmer specifies an interface to a new object type as a collection of ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept", Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....to make the structure of the expected arguments explicit. Functions are translated to #L agents that wait for requests at a channel that, by convention, is associated to the name of the function. return e returns the expression e. In general, this term is used to specify an early return [Gen81] run e invokes a function denoted by the form expression e asynchronously, i.e. it does not yield a result. ident(e 1 ) e n ) in em] invokes the function ident with the actual arguments e 1 , e n synchronously. If in em is specified, the function is invoked using em as ....

Morven Gentleman. Message passing between sequential processes: the reply primitive and the administrator concept. Software -- Practice and Experience, 11:435--466, 1981.

....in effect to have at least two separate threads of control, namely one for communication and another one for computation. For these purposes lightweight processes, i.e. PEACE threads, are the best choice. The benefit of this approach is a general improvement in structuring concurrent programs [10]. The request response model implies that a cliett issues the request message to a se ve and implicitly awaits the response message. In terms of PEACE, the issuing of the request message blocks the client thread . A server thread is blocked in cases where its request message queue is empty. In ....

W. M. Gentleman, "Message Passing between Sequential Processes: the Reply Primitive and the Administrator Concept", Software Practice and Experience, Vol. 11, pp. 435 466, 1981.

....task can continue to forward the request further to other responding tasks. The last responding task in the series sends a reply directly to the blocked task. This type of behavior occurs when a task acts as an administrator manager by dispatching service requests to a pool of worker tasks [50] or as a form of rate control for a task pipeline. E n E n interaction type task identifier list of service requests list of activities , E n V n n 1 n 2 . n i E n E n i A n e 1 . E n SCE97 05 Page 8 Besides entries that describe service ....

W.M. Gentleman. "Message passing between sequential processes: the reply primitive and the administrator concept." Software -- Practice and Experience, 11:435--466, 1981.

....in conjunction with the Common Prototyping Language project. 1 1 INTRODUCTION Writing distributed programs is difficult for programmers, and even more difficult when high performance is required. Many mechanisms to achieve better performance in distributed programming have been proposed [3, 12, 13, 14, 19]; however, in practice these mechanisms are hard to utilize, and do not take into account the burden placed on programmers who already encounter difficulty in writing functionally correct programs. Furthermore, most of these mechanisms are expressed by special programming language constructs for ....

W. M. Gentleman. Message passing between sequential processes: The reply primitive and the administrator concept. Journal of Software Practice and Experience, Vol. 11:435--466, May 1981.

....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 addressed in order to provide adequate expressive power for COOP. These issues have been overlooked in these proposals which are based on oversimplified models of COOP. Although such models facilitate the use of inheritance they ....

....provide adequate expressive power for other message processing patterns. In particular, it is hard to address the concurrent programming issues known as nested monitors call[Lis77] and remote delays[LH83] These issues are illustrated in a concurrent programming pattern known as the administrator[Gen81] In this programming pattern an object, we call it the server, accepts requests from clients and makes a number of (sub)requests to other objects (the second level servers) to process the client s request. While a second level server processes a (sub)request, the server accepts and processes ....

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W.M. Gentleman. Message passing between sequential processes: the reply primitive and the administrator concept. Software-Practice and Experience, (11):435--466, 1981.

....by Office of Naval Research and a grant from the Siemens Corporation. 1 INTRODUCTION Writing distributed programs is difficult for programmers, and even more difficult when high performance is required. Many mechanisms to achieve better performance in distributed programming have been proposed [3, 12, 13, 14, 19]; however, in practice these mechanisms are hard to utilize, and do not take into account the burden placed on programmers who already encounter difficulty in writing functionally correct programs. Furthermore, most of these mechanisms are expressed by special programming language constructs for ....

W. M. Gentleman. Message passing between sequential processes: The reply primitive and the administrator concept. Journal of Software Practice and Experience, Vol. 11:435--466, May 1981.

....parse the open directives. Server tasks are used extensively in Harmony to provide a wide range of services to other tasks in the system, such as managing scarce resources or serializing access to peripheral devices. A server is implemented as a separate task, usually written as an administrator [4] so that it is never blocked when needed by a client task. To ensure that the server will be ready, each server is usually assisted by one or more specialized worker tasks, which take care of long operations, operations that do not have a bounded time to completion or operations that are more ....

W.M. Gentleman, "Message Passing Between Sequential Processes: The Reply Primitive and the Administrator Concept," Software Practice and Experience, Vol. 11, No. 5, May 1981, pp. 435-466.

....by the master. Contrary to the divide conquer paradigm, subordinate problems are not necessarily homogeneous. Furthermore, not all subproblems must be known from the start. They can also be created as a consequence of solving a previous subproblem, see also [19] The administrator concept [22] reverses the role of send and reply for the worker processes. A worker sends the administrator a report on completion of the last task assigned and a request to be assigned new work. The administrator replies to the worker when there is a new task for it. This organization avoids that the ....

....created process returns output ports to its input ports with the initialization message to enable other processes to communicate with it. A first characteristic collected for each application process is its type. Several process taxonomies based on interprocess communication have been proposed [10, 22, 36]. These taxonomies vary in the number of categories they include, but they all divide processes into three broad categories: workers, servers, and shells or coordinators. Shells are processes that create and connect other processes only. Server processes offer one or more services in an endless ....

W. Morven Gentleman. Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept. Software---Practice and Experience, 11:435--466, 1981.

....list of the resource amounts requested by all pending get requests. 4. 2 Reply scheduling The use of the message passing features and their support for reuse will be illustrated by a series of examples that are variations of the general concurrent programming structure known as the administrator[15]. The administrator is an object that uses a collection of worker objects to service requests. Client objects issue requests to the administrator and expect to get back replies to their requests. The administrator manages a collection of workers and delegates to them tasks that have to be done ....

Morven Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept," Software---Practice and Experience, vol. 11, 1981, pp. 435--466.

....exchange of an arbitrary number of messages, this must be managed outside the communication mechanism. The balanced request reply structure of RPC can lead to a loss of efficiency. Consider a system consisting of a set of clients, a set of servers and an administrator as developed by Gentleman in [Gentleman 1981]. In this system the function of the administrator is to remove the need for clients to hold information about the servers. Instead, client requests are sent to the administrator, which forwards them to a selected server. When a given service completes, the reply generated should be sent back ....

Gentleman, W. M., "Message Passing between Sequential Processes: the Reply Primitive and the Administrator Concept", Software --- Practice and Experience, Vol. 11, pp. 435-466, 1981.

....strong typing of objects in Smalltalk [John86] and in Owl [Scha86] with little or no attention paid to concurrency. Work on concurrent objects has been mostly limited to actor languages [Hewi77, Byrd82, Ther83] and other kinds of systems supporting message passing processes, such as Thoth [Gent81]. Hybrid is an object oriented programming language in which objects themselves are the active entities. We believe that, with some care, concurrency can not only be easily accommodated within an object oriented framework, but that the object oriented approach is exceptionally well suited for ....

....of activities In addition, we show how this framework can be consistently extended to accommodate concurrent sub activities and atomic actions. To illustrate the use of these mechanisms, we give several examples of objects that encapsulate: 1. pipelining 2. postactions 3. administration [Gent81] 4. triggering 5. constraints 1. The notion of class inheritance, though crucial to object oriented programming, is secondary to the idea of encapsulation. 3 Active Objects in Hybrid Furthermore, with the higher level constructs for composing concurrent subactivities and atomic actions, it ....

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W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept," Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....discriminated according to whether requests are scheduled by an explicit acceptance, by activation conditions or by means of reflective computation: 1. A secondary issue is whether further activity related to a request may continue after the reply has been sent as in the Send Receive Reply model [11], but this can also be seen as concern of internal concurrency where follow up activity is viewed as belonging to a new thread. Request Scheduling UNCONDITIONAL No Synchronization with the state of the target ADA packets, Smalltalk80, Emerald, Trellis Owl. EXPLICIT ACCEPTANCE The execution of the ....

.... allow existing code to cooperate gracefully with modifications and extension [17] 32] In order to compare the design choices and their combinations with respect to the reuse requirements, we shall refer to an instance of a generic concurrent program structure: the administrator inspired by [11]. The administrator is an object that uses a collection of worker objects to service requests. An administrator application consists of four main kinds of components. The clients issue requests to the administrator and get back results. The administrator accepts requests from multiple ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept," Software-Practice and Experience, vol. 11, pp. 435-466, 1981.

....[13] As a result, all other processes are connected to the Enterprise process, indicated by the dashed lines. The second process to consider is the manager process. A manager is used with a replicated asset to control the workers using the administrator concept found in distributed computing [9]. The administrator controls the replicated workers by queuing up messages until workers become available. The administrator is typically a separate 43 Receptionist Square Manager Square Worker Square Worker Cube Manager Cube Worker Cube Worker Enterprise Process Figure 3.8: A process diagram ....

W. M. Gentleman. Message passing between sequential processes: The reply primitive and the administrator concept. Software: Practice and Experience, 11(5):435--466, May 1981.

....rejected depending on the state of the object. Multiple concurrent clients: signatures do not capture the interleaving interactions of an object with multiple concurrent clients. Non client server protocols: alternative message passing protocols such as early reply [6] and send receive reply [3] are not expressible with signatures. Re use criteria: signatures do not provide enough information about the behaviour of a concurrent object to determine whether it is safe to use in a new context. Our approach to defining types of active objects is motivated by substitutability, and is based ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept," Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....languages: 1. Active entities (processes) communicate indirectly through shared passive objects. 2. Active entities communicate directly with one another by message passing. The first approach is typical of languages like Modula 2 [40] whereas the second is adopted by, for example, Thoth [15] and various Actor languages [2] See [5] for an excellent survey of concurrent programming languages and notations. These same approaches are used in object oriented programming languages in order to structure concurrent applications, though they result in different object models. If we adopt ....

W.M. Gentleman, "Message Passing Between Sequential Processes: the Reply Primitive and the Administrator Concept," Software -- Practice and Experience, vol. 11, pp. 435-466, 1981.

....object send an output to another object. Filters are often arranged linearly to form pipelines, and # peers, which collaborate with other peers to produce some result, these peers not being assigned fixed cli ent or server roles. To these we add the administrator described in Gentle man [6]. This useful object acts as an intermediary between clients and servers, it receives client requests and forwards them to servers selected as appropriate, possi bly adapting the request to the format required by the selected server. The servers replies are sent directly to the requesting ....

Gentleman, W. M., "Message Passing between Sequential Processes: the Reply Primitive and the Administrator Concept", Software --- Practice and Experience, Vol. 11, pp. 435-466, 1981.

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W.M. Gentleman. Message Passing Between Sequential Processes: The Reply Primitive and the Administrator Concept. Software Pract. Exper. 11(5): 435--466; 1981.

....and if the value at that location can change, then there is a possibility of a critical race where the result of the program depends on when which task reads and when which task writes the value. Various systems have provided different mechanisms for dealing with the synchronization problem [2 4], including semaphores, monitors, conditional critical regions, rendezvous, and several kinds of message passing. Harmony addresses the problem by a paradigm for structuring multitask programs, using four primitives that provide message passing. A message, in Harmony, is a variable length ....

....ready with the data, it can transfer the data to B in a reply, with which A will not block but will continue to execute, and B will also resume execution in parallel. When B finishes processing the data, it can send to A again, returning any results and preparing to repeat the cycle. The paradigm [2] is that, in general, tasks do not use resources directly; for example, several tasks will not all access a location in memory that can change. Instead, each such resource is owned by a single task, 10 and operations on the resource are performed by that task on behalf of other tasks that have ....

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W.M. Gentleman. "Message passing between sequential processes: the reply primitive and the administrator concept." Software Pract. Exper. 11(5): 435--466; 1981.

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Morven Gentleman. Message passing between sequential processes: the reply primitive and the administrator concept. Software|Practice and Experience, 11(5), 1981.

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W. M. Gentleman, `Message passing between sequential processes: the reply primitive and the administrator concept', Software-Practice and Experience, 11, 435--466 (1981).

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W. M. Gentleman, `Message passing between sequential processes: the reply primitive and the administrator concept', Software---Practice and Experience, 11, 435--466 (1981).

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GENT81 Gentleman, W. M. Message Passing Between Sequential Processes: The Reply Primitive and the Administrator Concept. Software---Practice and Experience, v11, pp. 435-466, 1981.

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