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 Policies Negotiation
Chapter 17 3Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Why Organizations? Organizations consist of agents
(business partners) providing or using services
Organizations Relate well to human organizations Promote coherence in service
interactions Offer a conceptually natural, high-
level basis for understanding and designing service interactions
Chapter 17 4Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Organizations Organizations nest, though
usually not as trees All organizations are
agents Some agents are
organizations Organizations help overcome
limitations of individuals in Reasoning Capabilities Perception Lifetime, persistence
Chapter 17 5Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Three Kinds of Organizations
Concrete: agents playing roles Configured, run-time concept
Abstract (templates): roles and relationships among roles Design-time concept
Institutions: part abstract and part concrete Run-time concept, but the membership can
change Example: eBay, where buyers and sellers can
change but eBay itself is a fixed participant
Chapter 17 6Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Legal Abstractions Contracts Directed obligations Hohfeldian concepts Compliance
Chapter 17 7Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Contracts as Service Agreements Contracts structure interactions
(i.e., service engagements) among autonomous parties People and corporations Governmental agencies
Compare with contracts in programming Each needs a computational
representationKey questions: how to create,
modify, perform, or monitor contracts
Chapter 17 8Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Motivation for Contracts Provide a basis for service
agreements Crucial in open environments Emphasize public behavior:
observable by others Constrain behavior: limit autonomy Mostly disregard internal
implementations, thus supporting heterogeneity
May expose some implementation
Chapter 17 9Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Legal Concepts Inherently multiagent: about
interactions among autonomous parties
Directed obligations One party being obliged to another
party Multiagent flavor
Contrast with traditional deontic logic Zero-agent: it is obligatory that … One-agent: you are obliged to do …
Chapter 17 10Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Rights The rights or claims a party has on
another party Not the right (ethical) thing to do
The claims of one party are the duties of another: claim is a correlate of duty
Chapter 17 11Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Hohfeldian Concepts: 1 The term right is used ambiguously Sixteen concepts distinguish the
main situations: Four main concepts Their correlates Their negations Their negations’ correlates
Chapter 17 12Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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
Chapter 17 13Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Commitments A commitment
Involves three parties: a debtor commits to a creditor within an organizational context
Is scoped by its (organizational) context May be manipulated, subject to additional
commitments Is public (unlike beliefs)
Commitments provide Flexible interactions, thus promoting
coherence A basis for judging compliance
Chapter 17 14Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Manipulating Commitments
Operations on commitments: Create Discharge (satisfy) Cancel Release (eliminate) Delegate (change debtor) Assign (change creditor)
Metacommitments constrain the manipulation of commitments
Chapter 17 15Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Commitments for Contracts
A contract is a set of related commitments Provides a notional context to the
commitments Applies between specified parties, in a
context (e.g., UCC, real-estate, Internet commerce)
In contrast to commitments, other approaches: Single-agent focused, e.g., deontic logic Don’t handle organizational aspects of
contracts Don’t accommodate manipulation of
contracts
Chapter 17 16Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
SoCom: Sphere of Commitment
A computational abstraction based on organizations
An institution with additional features Involves roles (abstract) or agents
(concrete) A witness for the commitment
Trusted party to decide satisfaction or violation
A locus for testing compliance and enforcing corrections (e.g., compensation)
- Munindar Singh and Michael Huhns
SoComs and Structure A SoCom inherits policies from
surrounding (contextual) SoCom E.g., UCC applies to commercial
interactions Inherited policies can conflict because
of Nonunique nesting When agents play multiple roles
Chapter 17 18Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Virtual Enterprises (VE)A VE offers commitments
beyond those of its members to support business atomicity
Sellers come together with a new proxy agent called VE
Example of VE agent commitments: Entertain order updates Notify on change of
order Price guarantee Delivery date
guarantee
Chapter 17 19Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
A Selling VE (Composition Example)
Customer 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
Chapter 17 20Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Teams
Tightly knit organizations Goals shared by all team members Commitments to help team
members Commitments to adopt additional
roles and offer capabilities on behalf of a disabled member
Chapter 17 21Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Teamwork
When a team carries out some complex activity Negotiating what to do Monitoring actions jointly Supporting each other Repairing plans
Chapter 17 22Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
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)
Chapter 17 23Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Negotiation Mechanism Attributes
Efficiency Stability Simplicity Distribution SymmetryE.g., sharing book purchases, with
cost decided by coin flip
Chapter 17 24Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
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 each bidder to bid its
true valuation
Chapter 17 25Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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
Chapter 17 26Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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
Chapter 17 27Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Problem Domain Hierarchy
Worth-Oriented Domains
State-Oriented Domains
Task-Oriented Domains
Chapter 17 28Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Task-Oriented Domains: 1 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
Chapter 17 29Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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
Chapter 17 30Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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?
Chapter 17 31Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Zeuthen StrategyOffer 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)
Chapter 17 32Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
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
Chapter 17 33Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and
Michael Huhns
Chapter 17 Summary Organizations are a natural
metaphor for understanding and designing systems of services
Organizations provide a basis for realizing coherent interactions Legal and contractual concepts such
as commitments Teamwork Understanding and formalizing
negotiation
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