chapter 17: organizations service-oriented computing: semantics, processes, agents – munindar p....

Chapter 17:Organizations

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

Chapter 17 2Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and

Michael Huhns

Highlights of this Chapter

Contracts Spheres of Commitment Achieving Collaboration via

Conventions Policies Negotiation


Michael Huhns

Ethical Abstractions

Agents that are members of a society must have an ethics and a philosophy. This requires the development of components for

Deontological ethics Teleological ethics Consequentialism Duties Obligations Applying ethics


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Motivation

The ethical abstractions help us specify agents who act appropriately

Intuitively, ethics is just the basic way of distinguishing right from wrong

It is difficult to separate ethics entirely from legal, social, or even economic considerations


Michael Huhns

Right and Good

Right: that which is right in itself Good: that which is good or

valuable for someone or for some end


Michael Huhns

Deontological vs. Teleological

Deontological theories right before good being good does not mean being right ends do not justify means

Teleological theories good before right something is right only if it maximizes

the good ends justify means


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Deontological Theories

Constraints negatively formulated narrowly framed

e.g., lying is not not-telling-the-truth narrowly directed at the agent’s

specific action not its occurrence by other means not the consequences that are not

explicitly chosen, i.e., only works for consequences that are explicitly chosen


Michael Huhns

Double Effect

Deontological theories distinguish intentional effects from foreseen consequences

An action is not wrong unless the agent explicitly intends for it to do wrong legitimizes inaction even when inaction

has predictable (but unintended) effects shut down bank ATM for diagnostics even

if that might leave someone without cash


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Kant’s Categorical Imperative Whatever maxim an agent uses

must be universalizable, i.e., in the society of agents respect for others (no lying or

coercion) so they can consent false promising is unacceptable,

because if all did, their society would not function

agents’ maxims are uncertainly inferred from their actions


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Teleological Theories

Based on how actions satisfy various goals, not their intrinsic rightness comparison-based preference-based


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Consequentialism

An agent should promote whatever values it adopts

actions are instrumental in the promotion

honor the values only if doing so promotes them


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Utilitarianism

This is the view that a moral action is one that is useful

must be good for someone good may be interpreted as

pleasure: hedonism preference satisfaction: microeconomic

rationalism (assumes each agent knows its preferences)

interest satisfaction: welfare utilitarianism aesthetic ideals: ideal utilitarianism


Michael Huhns

Prima Facie Duties

What agents need to decide actions are not just universal principles (each can be

stretched) not just consequences but also a regard for their promises and duties

Agents have prima facie duties to help others, keep promises, repay kindness,...

no ranking among these highly defeasible conclusions, e.g., steal to

feed kids


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Obligations

Obligations are for deontological theories, those

that are impermissible to omit for teleological theories, those that

most promote good for contract-based theories, those

that an agent accepts


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Applying Ethics/1

The ethical theories are theories of justification not of deliberation

An agent can decide what basic “value system” to use under any approach


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Applying Ethics/2 The deontological theories

Are narrower Ignore practical consideration But are only meant as incomplete

constraints (out of all right actions, the agent can choose any)

The teleological theories Are broader Include practical considerations But leave fewer options for the agent, who

must always choose the best available alternative


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Applying Ethics/3

The ethical approaches are single-agent in orientation implicitly encode other agents

An explicitly multiagent ethics would be an interesting topic for study


Michael Huhns

Legal Abstractions

Contracts Directed obligations Hohfeldian concepts Compliance


Michael Huhns

Legal Concepts

Because law involves the interactions of citizens with one another and with the government, the legal abstractions have been richer in multiagent concepts

Traditional formalisms for legal reasoning, however, are often single-agent in orientation, e.g., deontic logic (the logic of obligation, “obliged to do p”)


Michael Huhns

Contracts

Much of the law is about the creation and manipulation of contracts among legal entities people corporations governmental agencies

The law is the study of how to break contracts!


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Motivation

The legal abstractions provide a basis for agents to enter into contracts, e.g., service agreements, with each other

Contracts are about behavior important in open environments


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Directed Obligations

Contracts lead naturally to one party being obliged to another party more precise notion of obligation than

in traditional deontic logic two-party concept has a more

multiagent flavor


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Rights

The rights or claims a party has, as opposed to the right (ethical) thing to do.

The claims of one party are the duties of another: claim is a correlate of duty


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Hohfeldian Concepts/1

Hohfeld discovered that “right” is used ambiguously and proposed a uniform terminology to distinguish the various situations. Sixteen concepts result: Four main concepts Their correlates Their negations Their negations’ correlates


Michael Huhns

Hohfeldian Concepts/2

Claim-duty: as above Privilege-exposure: freedom from

the claims of another agent Power-liability: when an agent can

change the claim-duty relationship of another agent

Immunity-disability: freedom from the power of another agent


Michael Huhns

Organizations

Organizations are larger-scale than single agent, goal-oriented, and with knowledge and memory beyond individual

Organizations help overcome the limitations of agents in

reasoning capabilities perception lifetime and persistence

Concretely, organizations consist of agents acting coherently

Abstractly, organizations consist of roles and commitments among the roles – these form a sphere of commitment


Michael Huhns

Coherence and Commitments

Coherence is how well a system behaves as a unit. It requires some form of organization, typically hierarchical

Social commitments among agents are a means to achieve coherence. An agent’s commitment to another agent or to its society

Is unidirectional Arises within a well-defined scope or

context Is revocable with restrictions Enables coordination through the

ordering and occurrence of actions by the agents


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Commitments for Contracts

Commitments capture contracts. Importantly, commitments are

Public (unlike beliefs and intentions) Can be used as the basis for compliance Contracts apply between parties, in a

context Other approaches are:

Single-agent focused, e.g., deontic logic Don’t handle organizational aspects of contracts Don’t accommodate manipulation of contracts


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Manipulating Commitments

Operations on commitments: Create Discharge (satisfy) Cancel Release (eliminate) Delegate (change debtor) Assign (change creditor)

Metacommitments constrain the manipulation of commitments


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SoCom: Sphere of Commitment

An organization that provides the context or scope of commitments among relevant roles (abstract) or agents (concrete) Serves as a witness for the

commitment, i.e., knows that the commitment exists

Helps validate commitments and test for compliance

Offers compensations to undo members’ actions


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Virtual Enterprises (VE)

Two sellers come together with a new proxy agent called VE

Example of VE agent commitments: Notify on change Update orders Guarantee the price Guarantee delivery

date


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A Selling VECustomer Virtual Enterprise Hose Seller Valve Seller

I would like to buy a valve with inputdia of 43, two matching hoses, andof price up to $50.00

Order placed; 1 valve idia = 43Odia = 43. 2 hoses dia = 43Charge = $14.83 Sell two 43 dia hoses

Order is ready

Order revised; 1 valve idia = 43odia = 21, hose dia = 43, andhose dia = 21. Charge = $14.83

Order processed

valve input dia = 43, output dia 43 discontinuedvalve input dia = 43, output dia 21 recommended

Cancel previous order

Sell one valve with input dia 43, output dia 21

Order is ready

Yes

Two 43 dia hoses in stock?

One valve with input dia 43, output dia 43 in stock?

Yes

One 43 dia & one 21dia hose in stock?

Yes

Sell one 43 dia & one 21dia hose

Order is ready


Michael Huhns

Teams

Tightly knit organizations Shared goals, i.e., goals that all

team members have Commitments to help team-

members Commitments to adopt additional

roles and offer capabilities on behalf of a disabled member


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Teamwork

When a team carries out some complex activity Negotiating what to do Monitoring actions jointly Supporting each other Repairing plans


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Negotiation

Negotiation is central to adaptive, cooperative behavior

Negotiation involves a small set of agents

Actions are propose, counterpropose, support, accept, reject, dismiss, retract

Negotiation requires a common language and common framework (an abstraction of the problem and its solution)


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Negotiation Mechanism Attributes

Efficiency Stability Simplicity Distribution Symmetrye.g., sharing book purchases, with

cost decided by coin flip


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Negotiation among Utility-Based Agents

Problem: How to design the rules of an environment so that agents interact productively and fairly, e.g.,

Vickrey’s Mechanism: lowest bidder wins, but gets paid second lowest bid (this motivates telling the truth?? and is best for the consumer??)


Michael Huhns

Negotiation

A deal is a joint plan between two agents that would satisfy their goals

The utility of a deal for an agent is the amount he is willing to pay minus the cost to him of the deal

The negotiation set is the set of all deals that have a positive utility for every agent. The possible situations for interaction are

conflict: the negotiation set is empty compromise: agents prefer to be alone, but will agree

to a negotiated deal cooperative: all deals in the negotiation set are

preferred by both agents over achieving their goals alone


Michael Huhns

Negotiation Mechanism

The agents follow a Unified Negotiation Protocol, which applies to any situation. In this protocol,

The agents negotiate on mixed-joint plans, i.e., plans that bring the world to a new state that is better for both agents

If there is a conflict, they “flip a coin” to decide which agent gets to satisfy his goal


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Problem Domain Hierarchy

Worth-Oriented Domains

State-Oriented Domains

Task-Oriented Domains


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Task-Oriented Domains

A TOD is a tuple <T, A, c>, where T is the set of tasks, A is the set of agents, and c(X) is a monotonic function for the cost of executing the set of tasks X

Examples deliveries: c(X) = length of minimal path that visits X

postmen: c(X) = length of minimal path plus return

databases: c(X) = minimal number of needed DB ops


Michael Huhns

Task-Oriented Domains (2)

A deal is a redistribution of tasks Utility of deal d for agent k is

Uk (d) = c(Tk) - c(dk) The conflict deal, D, is no deal A deal d is individual rational if d>D Deal d dominates d’ if d is better for at least

one agent and not worse for the rest Deal d is Pareto optimal if there is no d’>d The set of all deals that are individual rational

and Pareto optimal is the negotiation set, NS


Michael Huhns

Monotonic Concession Protocol Each agent proposes a deal If one agent matches or exceeds what

the other demands, the negotiation ends Else, the agents propose the same or

more (concede) If no agent concedes, the negotiation

ends with the conflict dealThis protocol is simple, symmetric, distributed, and guaranteed to end in a finite number of steps in any TOD. What strategy should an agent adopt?


Michael Huhns

Zeuthen Strategy

Offer deal that is best among all deals in NS Calculate risks of self and opponent

R1=(utility A1 loses by accepting A2’s offer) (utility A1 loses by causing a conflict)

If risk is smaller than opponent, offer minimal sufficient concession (a sufficient concession makes opponent’s risk less than yours); else offer original deal

If both use this strategy, they will agree on deal that maximizes the product of their utilities (Pareto optimal)

The strategy is not stable (when both should concede on last step, but it’s sufficient for only one to concede, then one can benefit by dropping strategy)


Michael Huhns

Deception-Free Protocols

Zeuthen strategy requires full knowledge of

tasks protocol strategies commitments

Hidden tasks Phantom tasks Decoy tasks

P.O. A1 (hidden)

A1 A2


Michael Huhns

Chapter 17 Summary

chapter 17: organizations service-oriented computing: semantics, processes, agents – munindar p....

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