organizations n.
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  1. CISC 887: Internet Information Gathering ORGANIZATIONS Sachin Kamboj

  2. Outline • Need for organizations • What is an organization? • Organizational structure • Organizational paradigms • Hierarchies • Holarchies • Coalitions • Teams • Societies • Markets • Case Study

  3. Need for organizations • Goal: • Design a multiagent system to solve a problem • For example: • Information gathering • Biological workflow enactment • Distributed vehicle monitoring • Hospital scheduling • Insert your favorite application here

  4. Need for organizations • System needs to be designed at two levels: • Micro-architecture (Internal architecture) • Type of agents • Simple reflex agents • Model-based reflex agents • Goal-based agents • Utility-based agents • Learning agents • Type of reasoning • Internal problem representation • Macro-architecture • Focus of rest of this talk!!!

  5. Need for organizations • Macro-architecture level: • Task structure • Breakup of problem into subgoals • Dependencies between methods • Number of agents needed • Task and resource allocation • Coordination mechanism • Macro-architecture design involves: • ORGANIZATION • Creating an organizational structure • Instantiating the structure

  6. Example task structure From Lesser et. al.: Evolution of TAEMS/GPGP domain independent coordination framework

  7. What is an organization? • No universally accepted definition • Organizations emerge whenever agents work together in a shared environment. Organizations reflect the structure of the interactions of the participating agents and are engaged in tasks and goal oriented behavior. • Singh.05 • Organizations are a consciously coordinated social entity, with a relatively identifiable boundary, that functions on a relatively continuous basis to achieve a common goal or a set of goals. • Robbins.89

  8. What is an organization? • A long-term commitment made by the agents to a particular way of handling the cooperative tasks. • So and Durfee.93 • Something that binds agents together to achieve effective coordination towards some common goal. • Barber.01

  9. What is an organization? • Organizations (adapted from Carley and Gasser.99): • are composed of cooperative agents working together towards the achievement of some common goal • goal directed • engaged in one or more tasks/activities • allow the effective coordination of agent activities towards the achievement of their common goals • are reasonably long term in duration: • having knowledge, culture, memories, history, and capabilities distinct from any single agent • able to affect and be affected by the environment • are characterized by an organizational structure • having legal standing distinct from that of individual agents

  10. Organizational structure • Consists of: • roles • parts played by the agents in the solution to the problem • reflect long term commitments made by the agents in question to a certain course of action • relationships • coordination relationships between subparts of a problem • Is used to: • limit the scope of interactions • reduce or manage uncertainty • increase redundancy • provide strength in numbers

  11. Organizational design • Is there a best way to organize? • NO!!! • All ways of organizing are not equally effective • The organizational structure will depend on: • The task structure • The environmental conditions • Resource availability • Task deadlines • Approaches to organization design • Implicit • emerges as a result of multiagent interaction • Explicitly designed • At design time • At run-time

  12. Organizational paradigms may be differentiated based on: Type of multiagent system Open system Closed system Type of agents Cooperative Competitive Duration Short term Long term Hierarchies Holarchies Coalitions Teams Congregations Societies Federations Markets Matrix Compund (From Horling 05) Organization paradigms

  13. Organizational paradigms • Hierarchies: • Agents are organized in a tree like structure • Data travels up. • Control and authority travels down • Reflect natural task breakup (HTNs) • Types: • Simple • Uniform • Formation through various means like contract net

  14. Organizational paradigms • Holarchies: • Hierarchical nested structures • Composed of holons • groups of agents that can be viewed as a single entity (agent) • part of larger hierarchy • characterized by partial autonomy of members • allows reasoning about individual holons instead of agents • easily applied to domains in which goals can be broken up into subgoals that can be assigned to the individual holons

  15. Organizational paradigms • Coalitions: • are subsets of agents • are goal directed • short-lived • formed with a purpose in mind • dissolves when need no longer exists • characterized by a flat organizational structure • coalitions may overlap (agents may be a member of two or more coalitions) • agents are self-interested • incentive for formation: • value should be super-additive • cost should be sub-additive

  16. Organizational paradigms • Teams: • consist of cooperative agents • that agree to work together • attempt to maximize the utility of the whole team • as opposed to individual agents • type and pattern of interactions is arbitrary • agents take on one or more roles as required • agents explicitly reason about and represent team-level behavior: • shared goals • mutual beliefs • team-level plans • how actions affect team utility

  17. Organizational paradigms • Societies: • long-term organizations • inherently open • agents have • different goals • varied levels of rationality • heterogeneous capabilities • provide a common domain through which agents can act and interact • impose constraints on the behavior of agents • by using social laws, norms and conventions • may themselves be made up of different ‘organizations’ • allow flexible interactions between the agents

  18. Organizational paradigms • Markets: • Buying agents request/place bids for a common set of items • Sellers process bids and determine the winner • Multiagent system is a producer-consumer system modeled on real-world market economies. • agents are competitive • open systems • as long as rules are followed • Applications: • To sell goods • Factory Scheduling • Query Processing

  19. Case study • A dynamically formed hierarchical agent organization for a distributed content sharing system • Haizheng Zhang and Victor Lesser University of Massachusetts, Amherst • Published in proceedings of the International Conference on Intelligent Agent Technology, 2004 • Investigates the role of an agent organization in a large scale content retrieval system

  20. Case study • Each agent has its own collection of documents • also include a local search engine • Agents are cooperative • Any agent may receive a query form the user: • query is propagated to other agents • agents perform local search • agents return relevant documents • results from multiple agents are merged together • using some mechanism not discussed • Unstructured/flat P2P agent network performs poorly • Propose a multi-level topical hierarchical structure • System consists of two parts: • A mechanism for hierarchical organization formation • A content aware search algorithm

  21. Case study • Agents have two roles: • group-mediator • whether a new agent should be added to the group • when to reorganize the group • selection of group members to process a query • propagation of queries to non-group members • query-processor • performs a local search of its collection • All non-leaf agents take on both roles • Leaf agent only take on query processor roles

  22. Case study

  23. Case study • Collection information • collection • actual stored documents • collection model • a statistical signature/summary of a collection • is propagated to other agents • So that other agents know what info is available • Local search engine • searches for relevant documents in the collection

  24. Case study • Control unit • accepts user queries • decides whether queries should be processed by one or more group members • determine order of other agents/groups that the query should be forwarded to • Agent View • contains information about the existence and structure of other agents in the network • also contains collection models of the other agents

  25. Case study • Topic-based hierarchical structure • Content Group: • A set of agents that store collections on the same topic • Consist of: • A mediator • All agents which connect to the mediator, directly or indirectly through upward links

  26. Not Accept! B Join? Join? A D C Not Accept! Join? Not Accept! Case study Hierarchy Generation E Scenario 1: Agent E joins the system as a top level mediator

  27. Join? Not Accept! B A D Join? Group Invitation! C Join? Not Accept! F Case study Hierarchy Generation E F Scenario 2: Agent F joins the group led by agent E

  28. Join? Join? B A D Group Invitation! Merge Request C Join? Merged Join? I F Group Invitation! Case study Hierarchy Generation E I G H G Scenario 3: Agent joins a top-level mediator (E) that is fully loaded

  29. Case study Searching A B E C D F G H Query I J K Phase 1: Propagation of query to top level mediators and similarity calculation

  30. Case study Searching A B E C D F G H I J K Phase 2:Propagation of query to agents for local searching

  31. References • K. S. Barber and C. E. Martin. Dynamic reorganization of decision-making groups. In AGENTS ‘01: Proceedings of the fifth international conference on Autonomous agents, pages 513-520, New York, NY, USA, 2001. ACM Press. • Kathleen M. Carley and Les Gasser. Computational organization theory. In Gerhard Wiess, editor, Multiagent Systems: A Modern Approach to Distributed Artificial Intelligence, pages 299-330, Cambridge, MA, 1999. MIT Press. • Y. So and E. Durfee. An organizational self-design model for organizational change. In AAAI-93 Workshop on AI and Theories of Groups and Organiza- tions: Conceptual and Empirical Research, pages 8ミ15, Washington, D.C., July 1993 • Bryan Horling and Victor Lesser. A survey of multi-agent organizational paradigms. Knowledge Engineering Review, 2005. • S. Robbins. Organization Theory - Structure Design and Applications. Prentice-Hall, Englewood Cliffs, 1989. • Haizheng Zhang and Victor Lesser. A Dynamically Formed Hierarchical Agent Organization for a Distributed Content Sharing System . In Proceedings of the International Conference on Intel ligent Agent Technology (IAT 2004), pages 169-175, Beijing, September 2004. IEEE Computer Society.

  32. Questions?