Object Oriented systems bring new issues in software engineering, including the support for distributed information systems. Pairing distributed systems with object paradigms results in a distributed object paradigm. Choosing the most efficient distributed object design is a multi-criteria decision problem. Performance is a key criterion that allows software developers to be able to select the object-oriented design that best fits their requirements and hardware limitations. However, investigating and evaluating the performance of Distributed Object Oriented (DOO) systems is a challenge due to the complexity of interactions among objects. Classical techniques and methodologies of performance analysis are either unsuitable or unnatural to capture the performance behavior of object-oriented systems while preserving object-oriented characteristics. In this thesis, we investigate this problem and develop analytical models to study the performance of OO software that runs on single-node, distributed systems or pipeline architecture. We also develop a methodology to analyze and evaluate each model. The methodologies include: software computation, communication activities among objects, and object updating in case of the distributed environment. The developed performance models can be integrated with the design phase to enable the software engineer to explore software restructuring, allocation alternatives partitioning or scheduling methodologies. In many cases, the initial OO software does not have the best class distribution and may require restructuring. In this research, we utilize the performance-based model and the evaluation methodology to develop two new restructuring techniques; one for distributed object oriented systems and the other for software that runs on a pipelined architecture. The new techniques will efficiently restructure the OO software, fully exploit the system resources, and hence obtain better performance.

The purpose of this research was to evaluate the efficiency of a distributed simulation architecture which creates individual modules which are made self-scheduling through the use of a message-based communication system used for requesting input data from another module which is the source of that data. To make the architecture as general as possible, the message-based communication architecture was implemented using standard remote object architectures (Common Object Request Broker Architecture (CORBA) and/or Distributed Component Object Model (DCOM)). A series of experiments were run in which different systems are distributed in a variety of ways across multiple computers and the performance evaluated. The experiments were duplicated in each case so that the overhead due to message communication and data transmission can be separated from the time required to actually perform the computational update of a module each iteration. The software used to distribute the modules across multiple computers was developed in the first year of the current grant and was modified considerably to add a message-based communication scheme supported by the DCOM distributed object architecture. The resulting performance was analyzed using a model created during the first year of this grant which predicts the overhead due to CORBA and DCOM remote procedure calls and includes the effects of data passed to and from the remote objects. A report covering the distributed simulation software and the results of the performance experiments has been submitted separately. The above report also discusses possible future work to apply the methodology to dynamically distribute the simulation modules so as to minimize overall computation time. Schoeffler, James D. Glenn Research Center NCC3-572...

Distributed Object Computing teaches readers the fundamentals of CORBA, the leading architecture for design of software used in parallel and distributed computing applications. Since CORBA is based on open standards, it is the only effective way to learn object-oriented programming for distributed systems. This language independent book allows material to be taught using Java, C++ or other Object Oriented Programming Languages.

Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 36 (thesis year 1991) a total of 11,024 thesis titles from 23 Canadian and 161 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 36 reports theses submitted in 1991, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.