Date of Award


Document Type


Degree Name

Master of Arts (MA)


Computer Science


The integrated use of expert systems distributed on a network is a topic of practical importance. Through the proper integration methods, powerful expert systems could emerge. Several approaches exist for distributed problem solving, but most of them assume that the individual agents possess sufficient knowledge and skills to communicate and negotiate results and plans. In practice, however, what is needed is a simple, easy-to-implement, approach that allows the integrated use of a distributed (probably existing) set of expert systems or agents. In this thesis the OSDES approach (which stands for Open System of Distributed Expert Systems) is presented. It entails the open systems perspective (originated from Hewitt), as well as the centralized version of multiagent planning. This approach sets a minimum requirement which specifies the types of interfaces that OSDES can handle. Almost any expert system can interface with OSDES through input and output redirection at the user interface level. The heart of the integrated system is the Experts Directory Assistance (EDA) which is a service that all the agents in the system can utilize. The EDA keeps all the information about all the expert systems currently contributing to the system. Whenever an agent is added or removed, the EDA is notified to update its database. Another major part in the integrated system is the communicator, which acts as the mediator between the individual agents, as well as between the agents and the EDA. Each agent in the system has a communicator associated with it. The communicator also provides a user interface, and a simple scheduler to plan the execution sequence of the remote agents. The communicator incorporates a Generic User Interface (GUI), a Generic Agent Interface (GAD), a Distributed System Interface module (DSI), and a Kernel (or planner) module. The OSDES approach was implemented on the IBM-PC/AT running MS-DOS 3.3. The communicator and the EDA were written using Microsoft ‘C’ compiler version 5.1, and 1st-Class (an expert systems building tool) was used to develop the sample expert systems. To implement the communication protocols, a Remote Procedure Call (RPC) development tool (Netwise RPC) was used. The underlying network is an Ethernet based Novell 386 Local Area Network (LAN), but given the proper RPC compiler and libraries, any other LAN can be used. Further improvement includes developing new agent interfaces using memory mailboxes or interactive remote input and output. It also includes eliminating the current DOS limitations by adapting OSDES in a multi-threaded environment such as UNIX or OS/2. environment.


A Thesis Presented to the Department of Mathematics and Computer Sciences and the Faculty of the Graduate College University of Nebraska In Partial Fulfillment of the Requirements for the Degree Master of Arts University of Nebraska at Omaha. Copyright 1990 Semir Al-Schamma