1. Chapter 16: Multiagent Systems Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

2. Chapter 162Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter Applicability in Service-Based Systems Multiagent Architecture Agent Types Lifecycle Management Consistency Maintenance Modeling Other Agents Cognitive Concepts

3. Chapter 163Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Basic Problems of MAS Distributing control among agents Describing, decomposing, distributing tasks Interacting and communicating Representing goals, problem-solving states, and other agents Maintaining consistency, reconciling conflicts

4. Chapter 164Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns (de facto) Standard Agent Types

5. Chapter 165Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Brokerage Service Cooperates with a Directory Service An agent requests the Brokerage Service to recruit one or more agents who can provide a service Brokerage Service uses knowledge about the requirements and capabilities of registered agents to Determine the appropriate agents to which to forward a request for a service Negotiates with the agents to determine a suitable set of service providers Potentially learn about the properties of the responses example: Brokerage agent determines that advertised results from agent X are incomplete and seeks a substitute for X

6. Chapter 166Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns FIPA Agent Management System

7. Chapter 167Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Agent Management System: 2 Handles the creation, registration, location, communication, migration and retirement of agents. Provides the following services: White pages, such as agent location, naming and control access services, which are provided by the Agent Management System (AMS). Agent names are represented by a flexible and extensible structure called an agent identifier, which can support social names, transport addresses, name resolution services, amongst other things Yellow pages, such as service location and registration services, which are provided by the Directory Facilitator (DF) Agent message transport services

8. Chapter 168Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Java Agent Development Framework JADE, the most popular FIPA-compliant agent framework for multiagent systems: http://jade.tilab.com/ The most established of the publicly available agent frameworks (FIPA-OS and Zeus having died)

9. Chapter 169Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Consistency Maintenance across Services A truth maintenance system (TMS) helps maintain consistency Performs a form of propositional deduction Maintains justifications and explains the results of its deductions Updates beliefs incrementally when premises change TMSs help us Deal with atomicity Maintain modular models

10. Chapter 1610Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Architecture of TMS-Based Agent Problem solver: decides on actions TMS: maintains a network of beliefs based on the justifications relating them Problem Solver TMS justifications beliefs

11. Chapter 1611Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Knowledge Base Integrity Stability: believe everything justified validly; disbelieve everything else Well-Foundedness: no circular beliefs Logical consistency: no logical contradictions Completeness: find a consistent state if one exists, or report failure Problems arise when knowledge is distributed

12. Chapter 1612Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Distributed TMS Each agent has a justification-based TMS Each datum can have status OUT IN: valid local justification EXTERNAL: must be IN for some agent When a problem solver adds or removes a justification, the DTMS Unlabels data based on the changed justification Relabels all unlabeled shared data (in one or more iterations)

13. Chapter 1613Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Degrees of Logical Consistency Inconsistency: an agent is individually inconsistent Local Consistency: all agents are individually consistent Local-and-Shared Consistency: agents are locally consistent and agree about any data they might share Global Consistency: agents are globally consistent (union of KBs is consistent) The DTMS maintains local-and-shared consistency and well-foundedness

14. Chapter 1614Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Cooperative Service: 1 Client f3: afford(xcorp) IN r3: buy(X) :- query(Broker recommend(X)), afford(X) IN Broker f1: afford(xcorp) OUT f2: cash-rich(xcorp) IN r2: recommend(X) :- takeover-bid(X) IN r1: takeover-bid(X) :- cash-rich(X) IN ? recommend(?X)

15. Chapter 1615Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Cooperative Service: 2 Client f3: afford(xcorp) IN r3: buy(X) :- query(Broker recommend(X)), afford(X) IN Broker f1: afford(xcorp) OUT f2: cash-rich(xcorp) IN r1: recommend(X) :- takeover-bid(X) IN r2: takeover-bid(X) :- cash-rich(X) IN f3: recommend(xcorp) IN Shared with: Client; Justification: (f2 r1 r2) recommend(XCorp)

16. Chapter 1616Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Cooperative Service: 3 Client f3: afford(xcorp) IN r3: buy(X) :- query(Broker recommend(X)), afford(X) IN f4: recommend(xcorp) EXTERNAL Shared with: Broker; Justification: ( ) f5: buy(xcorp) IN Justification: (f3 f4 r3) Broker f1: afford(xcorp) OUT f2: cash-rich(xcorp) IN r1: recommend(X) :- takeover-bid(X) IN r2: takeover-bid(X) :- cash-rich(X) IN f3: recommend(xcorp) IN Shared with: Client; Justification: (f2 r1 r2)

17. Chapter 1617Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Cooperative Service: 4 Client f3: afford(xcorp) IN r3: buy(X) :- query(Broker recommend(X)), afford(X) IN f4: recommend(xcorp) EXTERNAL Shared with: Broker; Justification: ( ) f5: buy(xcorp) IN Justification: (f3 f4 r3) Broker f1: afford(xcorp) OUT f2: cash-rich(xcorp) IN --> OUT r1: recommend(X) :- takeover-bid(X) IN r2: takeover-bid(X) :- cash-rich(X) IN f3: recommend(xcorp) IN --> OUT Shared with: Client; Justification: (f2 r1 r2) relabel recommend(XCorp)

18. Chapter 1618Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Cooperative Service: 5 Client f3: afford(xcorp) IN r3: buy(X) :- query(Broker recommend(X)), afford(X) IN f4: recommend(xcorp) OUT Shared with: Broker; Justification: ( ) f5: buy(xcorp) OUT Justification: (f3 f4 r3) Broker f1: afford(xcorp) OUT f2: cash-rich(xcorp) OUT r1: recommend(X) :- takeover-bid(X) IN r2: takeover-bid(X) :- cash-rich(X) IN f3: recommend(xcorp) OUT Shared with: Client; Justification: (f2 r1 r2)

19. Chapter 1619Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 16 Summary Study multiagent systems because interactions among agents make them interesting Communication among agents is key, although markets (later chapter) only support implicit communication through prices Programming environments support agent interactions Consistency maintenance is a major challenge Agents must model agents; simple techniques are often adequate; more subtle techniques can require extensive reasoning power