The goal of this project was to develop part of an environment that would allow the creation of distributed applications using the actor model in an heterogeneous environment. The actor model is realized by ACT++, a C++ framework for building actor applications. This project is concerned only with the problems of the creation, destruction and the invocations of the methods of a remote server actor. A related project concerns the client activities and the message transfer. Three elements comprised the solution: a run-time loading entity using the facilities of a dynanlic linker called "DId," a query service to identify the classes present in an object file using a tool derived from the source-level debugger "GDB" and a directory service allowing both classes and actors to be located in memory. The solution was tested on several simple examples. The fundamental features of C++ and of the actor model have been retained in the distributed environment. The typing mechanisms used by C++ are preserved, and both polymorphic and overloaded functions are available. Regarding the actor model, the main components, namely actors, behaviors, messages and the replacement behavior are present. However, a choice had to be made concerning the communication model and the argument passing semantics. C++ and the actor model support synchronous and asynchronous communications, respectively. The latter was chosen, as our solution was based on the actor model and its message passing mechanism. C++ allows by reference parameters, while in the distributed environment, only by value parameters are allowed. It appears that the tools derived from GDB and DId could also be used as a software engineering tool, allowing the dynamic linking and unlinking of a class, the creation of objects of that class, and the invocation of its methods for testing purposes. / Master of Science

Master of Science

<p>The actor model provides a framework for writing concurrent programs. ACT ++ is an implementation of the actor model in C++, allowing concurrent programs to be written in an object-oriented style. In ACT++, each actor is an object possessing one or more independent threads of control. Version 2.0 of ACT ++ uses the PRESTO threads package. As PRESTO threads are available only for certain architectures and operating systems, its use does not meet one of the goals of ACT ++, namely portability among a variety of architectures. To facilitate portability, ACT++ 3.0 is written using the IEEE POSIX 1003.4a standard for threads (Pthreads). This project deals with the implementation of ACT++ 3.0, the testing of the implementation, and its performance.</p> / Master of Science

<p>The goal of this project was to develop part of the environment that would allow the creation of distributed applications in ACT++. ACT++ is a programming framework in which concurrent object-oriented programs can be written in C++. The concurrent objects in ACT ++ are called actors. Specifically, the project is concerned with the development of a communication infrastructure that configures a collection of heterogeneous machines for use in the distributed version of ACT++.</p> <p> A utility, "ActorControl," was implemented through which the user can specify how ACT ++ is to run on each of the nodes by means of a configuration file. The "ActorControl" utility starts a process on each of the nodes specified in the configuration file and establishes TCP socket based connections among all of them. To simplify the communication between the different nodes, a special type of actor called an interface actor is used. Instead of issuing communication requests directly to sockets, a request is directed to an interface actor that is responsible for that socket. A related project is concerned with the problems of creation, destruction and invocation of the methods on the remote machine.</p> <p> Thus the project consists of two parts. The first part is the implementation of the "Actor Control" utility that establishes socket connections among all the nodes participating in the distributed ACT ++. The second part is the implementation of the interface actors that are present at each end of the connection between any pair of machines.</p> / Master of Science

Submitted to the Faculty of Arts in fulfillment of the requirements for the degree of Doctor of Philosophy (D.Phil) in the Department of Communication Science at the University of Zululand, South Africa, 2004. / This dissertation focuses on the contribution of electronic communication (e-Communication) to knowledge management. It is based on an empirical survey of knowledge management practitioners in the private, public and NGO sectors in KwaZulu-Natal, South Africa. The major findings of this study are (1) that many knowledge management practitioners have not received any formal training in knowledge management, (2) that for most of them their practices are not informed by explicit knowledge management policies, (3) that there is no culture of sharing knowledge established within particular organisations, and finally (4) that knowledge managers are not using e-learning facilities to keep their knowledge of knowledge management current.

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