InterJournal Complex Systems, 294
Status: Submitted
Manuscript Number: [294]
Submission Date: 990706
Comment on manuscript revision number 47701
Caution! Agent Based Systems in Operation
Author(s): Bill Fulkerson

Subject(s): CX.64, CX.65

Category: Brief Article

Abstract:

This paper presents many distinctions to help practitioners choose when and how to apply agents. It highlights several major issues involved in the design and implementation of agent based applications. Specific solutions or actions are not. However, the authors do raise issues that merit serious consideration when applying agents to solve real problems. These issues are illustrated by typical examples that should be understood by most engineers. The paper contains these ten sections. The title and topical sentences from each section follow. 1. When to use Agents? The agency approach offers the power of problem decomposition and parallelism for tackling complex problems. The autonomous nature of agents also offers flexibility in dealing with uncertain situations and localized failures. 2. Agent Functionality. The optimal distribution of functionality among various agents in the system depends on factors, such as available communication bandwidth, processing capability of individual agents, real-time decision requirements, level of fault tolerance desired and the nature of the task to be performed. 3. Incorporating Values into Agents. Utility functions are used to specify values. In case utility function cannot be specified a priori, the agents could be equipped with learning mechanisms to judge the utility of their decisions and improve as the system evolves. 4. Incorporating Intelligence into Agents. It is important to balance learned and programmed behavior in agents. A strictly programmed agent will be rigid and inflexible, whereas a pure learned behavior may be time consuming and will not guarantee desired results. 5. Context and Ontological Issues. In order to achieve the overall goals, agents must communicate their goals and intents with other agents. Specification of a context plays an important part in the agent communications. One way of maintaining a common context is to use existing standard meta languages, such as KQML, XML, and KIF. 6. When Agents Make Mistakes. System designers need to pay close attention to the authentication and data consistency issues, and incorporate evaluation mechanisms in the agent architecture. Agents may need to securely log important transactions in order to maintain records and perform self-diagnostics. 7. Convergence and Negotiations. Agent based systems, especially when iterative negotiations are used, do not always guarantee convergence to a solution in a specific time period. Moreover, the optimality or robustness of the solutions are not assured. It is important to understand these limitations and plan appropriate tests to guarantee quality of the results generated by agent based systems. 8. System Level Issues. Agent based systems, like other asynchronous distributed environment, are faced with the system level issues, such as stalling, deadlock, cycling, etc. Arguably, a centralized observer or controller is the antithesis of the distributed decision making qualities of agents. However, most real world agent applications need some level of system monitoring in order to ensure error free operations. 9. Implementing Agent Systems. Agent based systems need a set of basic tools and services in order to implement them, such as birth/death services, communication channels, interaction protocols, etc. If the agents are mobile over heterogeneous systems they require additional capabilities for process migration. 10. Designing Optimal Agent Systems. The question of designing best agents for a particular task still remains unanswered. Moreover, the design of a society of agents which is ideally suited for solving a complex problem requires the use of prescriptive tools for analyzing distributed agent systems. The authors achieved their purpose of informing the general reader of areas of caution in the use of agents. While the tone of the paper may be interpreted to suggest caution the use of agents, this is not the case. This paper was originally chosen to balance two other papers on the applications of agents in a session on agent applications. Thus, the authors' cautionary tone reflects this appointed role rather than any specific opinion on their part.

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