Gaia Methodology for Agent-Based Systems: Analysis and Design, Slides of Multiagent Systems

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Agent Oriented Programming

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Software development methodologies

• Progress in software engineering has been made through new, powerful abstractions - Procedural abstraction - Abstract data types - Objects - Components
• If agents are to realize their potential as a software engineering paradigm, it is necessary to develop techniques specifically tailored to them.
• Current approaches (e.g. rational unified process) fails to capture the - Agents flexible, autonomous behaviour - The richness of interactions - Complexity of the agents organizational structures - Mobility and mutation

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Agent methodologies

• Numerous methodologies were proposed, which can be categorized as follows:
• Techniques using OO modelling techniques as their basis (GAIA, Agent UML, the BDI technique proposed by Kinny et. al.)
• Methodologies based on techniques form knowledge engineering, providing formal, compositional modelling languages suitable for verification of system structure and function.
• Methodologies taking existing formal languages such as Z, and specify agents systems in this framework.
• Methodologies developed specifically for agent systems. E.g. Cassiopeia based on the Contract Net model.

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GAIA

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Models of the Gaia methodology

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What kind of agents are handled

• Coarse-grain agent systems. E.g. each agent ~= Unix process.
• The goal is to obtain a system that maximizes some quality measure, but which might be sub-optimal for individual agents. Gaia is not intended for systems that admit the possibility of true conflict.
• Agents can be heterogeneous.
• The organization structure of the system is static, inter- agent relationships do not change over time.
• The abilities of the agents and their services do not change over time.
• The system contains a relatively small number of agents <

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Concepts:

• System: e.g. society of agents
• Roles
  • E.g. president, mailman, secretary
  • In an actual instantiation, these will be instantiated by actual persons / agents.
  • An agent can fulfill multiple roles, the same role can be taken on by multiple agents.
• A role is defined by four attributes:
  • Responsibilities: liveness properties + safety properties Docsity.com

The roles model

• Identifies the key roles of the system.
• Here a role can be viewed as a more or less abstract description of an entity’s expected functionality.
• Two things to specify:
• The permissions/rights associated with the role - A role will have associated with it certain permissions, related to the type and amount of resources that can be exploited when carrying onDocsity.com

Protocol definition

• A protocol definition consists of the following attributes:
• Purpose: brief text description of the nature of the interaction.
• Initiator: the role who is starting it.
• Responder: the role(s) with which the initiator interacts.
• Inputs: information supplied by the initiator while enacting the protocol Docsity.com

Analysis

• 1. Identify the roles in the system.
  • Output: prototypical roles model.
• 2. For each role identify and document the associated protocols.
     • Output: interaction model.
• 3. Using the protocol model as a basis, elaborate the roles model.
     • Output: fully elaborated roles model, which documents the key roles occuring in the system, their permissions and responsibilities, togetherDocsity.com

Models in the Gaia design process

• Agent model
  • The agent types that will make up the system
  • Agent instances which will be instantiated
  • Agent type tree: leafs are roles, agents are other nodes
  • No inheritance
• Services model
  • The main services that are required by each agent to realize the agent’s role.
  • For each service define inputs, outputs, Docsity.com

The Gaia design process

• Create an agent model:
  • Aggregate agent roles into agent types, and refine to form an agent type hierarchy
  • Document the instances of each agent type using instance annotations.
• Develop a services model, by examining activities, protocols, and safety and liveness properties of roles.
• Develop an acquaintance model from the interaction model and agent model. Docsity.com