Model-Based Detection of Emergent Behavior in Distributed and Multi-Agent Systems from a Component Level Perspective

Requirement elicitation is one of the most challenging and critical phases of the software development lifecycle. Many faults are introduced into the system as the result of incomplete requirements. An effective approach for the design of software systems is to describe system requirements using scenarios. A scenario, commonly expressed using a message sequence chart or a sequence diagram, is a temporal sequence of messages sent between system components. However despite their simplicity and expressive power, scenario-based specifications are prone to subtle deficiencies with respect to analysis and validation known as incompleteness and partial description. These deficiencies in scenario-based specifications are the prime cause of emergent behavior. Emergent behavior, also known as implied scenarios are behavior that the system exhibits but are not explicitly defined in its requirements. Emergent behavior is an important issue in the design of software systems; particularly ones with the lack of central control such as distributed and multi-agent systems. Detecting and removing emergent behavior during the design phase will lead to huge savings in deployment costs of such systems. In this thesis, a method for detecting emergent behavior in system requirements described using scenario-based specifications is proposed. The use of this methodology for a variety of different software systems such as distributed and multi-agent systems (MAS) is demonstrated. Furthermore this research contains methodologies for verifying the lack of existence of a particular emergent behavior in the software system. These methodologies have been demonstrated using various case studies such as distributed systems for a mine-sweeping robot and an online commerce application and a multi-agent system for a manufacturing system. Furthermore as this research aims to develop these methodologies into a software tool, the requirement and design documents as well as the prototype of this tool are presented in this thesis.