An Introduction to Agent Technologies

An Introduction to Agent Technologies Peter Wurman, NCSU Yelena Yesha, UMBC Olga Streltchenko, UMBC

Presentation Overview • Working definition of an agent • Agent characteristics and properties • Agent societies • Examples

Working definition of an agent • “Agents are active, persistent (software) components that perceive, reason, act, and communicate” • Huhns and Singh, 1998 • “An agent is an entity whose state is viewed as consisting of mental components such as beliefs, capabilities, choices, and commitments. [sic] In this view, therefore, agenthood is in the mind of the programmer.” • Shoham, 1993

Agent Program • Inputs = observations • Observations: states of the agent’s domain or environment • Outputs = actions • Actions: Speak, Search, Move, Bid ( o1, o2, … ) ( a1, a2, … ) Agent

Agents Environments • An agent must have a model of its domain and a model of other agents that it communicates with. • Properties of agents’ environment: • Observable • Dynamic • Discrete

Basic Characteristics • Delegation abilities: The owner or user of an agent delegates a task to the agent and the agent autonomously performs the task on behalf of the user. • An agent can decompose and/or delegate the task to other agents; • Once the task is complete the agent may need to report to the user/agent issuing the task.

Basic Characteristics (cont’d) • Agent communication languages and protocols: information exchange with other agents establishes a need for expressive communication and negotiation language. • KQML (Knowledge Query and Manipulation Language); • Used to allow information agents to assert interests in information services, advertise their own services, and explicitly delegate tasks and requests for assistance from other agents. • Can be used for developing a variety of inter-agent communication protocols that enable information agents to collectively cooperate.

Basic Characteristics (cont’d) • Self-representation abilities: the ability to express business and system aspects of its functionality, combine them into an application or implementation. • Self-describing, dynamic reconfigurable agents; • Facilitate composition (specification and implementation) of large-scale (distributed) applications.

Agent Mental State (BDI) • Beliefs–knowledge about the world and the effects the agent’s actions have on the world. • Desires–preferences over possible states of the world (goals). • Intentions–internal commitments made to achieve certain world states.

Example: Trading Agent Market Info User preferences Strategy synthesizer Auction rules Bidding strategy Model of other market participants Bids

Example: Trading Agent • Beliefs: auction rules, model of market • Desires: user preferences • Intentions: objects it has decided to buy/sell • Capabilities: place new bids • Observations: market information

Reactive Agent • Lookup table maps each observation, or series of observations, to an actionan = f(on), oran = f(o1,…, on) • Fast • Inflexible • Intractable for nontrivial domains

Rational Agents • Decision theoretic (economic) • Agent makes optimal decisions given its beliefs, goals, and intentions. • Logical • Agent makes decisions that are consistent with its beliefs, goals, and intention.

Boundedly Rational Agents • Agent makes optimal decisions given its beliefs, goals, intentions, and the limits of its computational abilities.

Learning Agent • An agent that updates its beliefs based on its observations • What can we learn? • Model of the world • New capabilities • Effects of our actions

Learning Agent • Learning task: • Learn w, where sn+1 = w(sn, an) • Types of learning • Supervised • Reinforcement • Unsupervised

Autonomy • Agent autonomy, with respect to • User = execution autonomy • Other agents = social autonomy • Designer autonomy, with respect to • Communication = interface autonomy • Architecture = design autonomy • Utility function = preference autonomy

Belief Representation • Knowledge level • The Wolfline runs from HC to CC • Logical level (declarative) • Connects(Wolfline,HC,CC) • Implementation level (procedural) public class Bus{ public string start = “HC”; public string end = “CC”; }

Benefits of Declaritivism • Modularity • Semantics • Inspectability • Learnability • Programmability

Other Properties of Agents • Lifespan: transient to long-lived • Modeling: of itself, the world, and other agents • Mobility: stationary or mobile • Memory: non to perfect recall

Agent Societies • Software infrastructure • Social organization

Software Infrastructure • Communication Channels • Common Ontologies • Service agents (i.e. directory agent)

Communication • ACL = agent communication language • Example: KQML • Content messages: tell, query, reply, etc. • Flow control: next, etc. • Generally do not prescribe semantics

Ontologies • Define the semantics of communication • Notoriously difficult • Employee = everyone on payroll • Employee = everyone receiving benefits

Social Organization • Homogeneous or heterogeneous • Self-interest v.s. cooperative • Social control structure • System evaluation

Emergent Behavior • Agents act • With limited, local knowledge • In self interest • System behaves • In globally desirable manner • Without central control • Adam Smith’s “invisible hand”

E-commerce example • Trading agents, again • Heterogeneous • Self-interested • Mediated • Game-theoretic evaluations

Legacy System Example User Agent Agent Agent Agent DB1 DB2 DB3

Personal Assistants • Agents that support a user’s task • Example (weak) • Dialogue based • Anthropoid • Cooperative ? • But has no goals of its own

Personal Assistants • Example: smart calendar/datebook that could • Negotiate appointments for me • Actively keep track of my contacts by searching the web • Learn priorities for my mail

Conclusion • Agenthood is a convenient description • Agents are described by beliefs, desires, and intentions • Agents select actions based on observations • Cooperating agents are a form of distributed computation • Self-interested agents can generate desirable emergent behavior

An Introduction to Agent Technologies