1. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Chapter 20: Social Service Selection
Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005
© Singh & Huhns

2. Highlights of this Chapter
Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Highlights of this Chapter
Reputation Mechanisms
Recommender Techniques
Referrals
Social Mechanism for Trust
Identity
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

3. Recommending Products vs. Services
Products (by a product vendor): often,
The recommender is the provider
Votes are known to the recommender
Votes are received prior to usage (buying)
Repetition is less likely (buy the same book?)
Services (by a service registry)
The recommender is not the provider
Votes are not necessarily known to recommender
Votes are given after usage
Repetition may occur, invisibly to registry
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

4. Reputation The agency (e.g., eBay) is the authority that
Authenticates users
Records, aggregates, and reveals ratings
Provides the conceptual schema for
How to capture ratings (e.g., numbers and text)
How to aggregate them
How to decay them over time
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

5. Service Communities Each principal
Provides services to others
Provides recommendations to others
Exploits services provided by others
Has a reputation
The agents assist their users and other agents in
Evaluating the services and referrals provided by others
Maintaining models of acquaintances
Deciding whom to contact for a service
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

6. Social Networks and Referral Chains
Referral chains in networks provide:
Way to identify a good provider
Way to judge the quality of a provider
Reason for a member to respond in a trustworthy manner
As the chains get longer
The trustworthiness of a recommendation decreases
The effort to find providers increases
Therefore, shorter chains are better
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

7. Distributed Treatment of Referrals
Receive request
Ask
Model asker
Follow referrals
Respond
Use
Rate; update
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

8. Agent Model for Referrals
Model each agent via its
Interest (services sought)
Expertise (services provided)
Models of its acquaintances representing their
Expertise (ability to provide good services)
Sociability (ability to provide accurate referrals)
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

9. Reputation Buildup and Collapse
A participant who begins to misbehave is detected
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

10. Small World Phenomenon
Milgram (1967): two individuals chosen at random in the U.S.A. are linked by a chain of 6 or fewer first-name acquaintances (empirical observation)
Six degrees of separation
Erdös numbers
Diameter of the connected Web: 20
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

11. Small-World Network Generated by perturbing a regular ring
A highly structured (clustered) network with just a few random edges
Random edges correspond to shortcuts
Yields high clustering and short paths
Direct relationships between agents who primarily belong to distinct subcommunities
Shortcuts: weak ties
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

12. Quality Relates Inversely to Clustering
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

13. Weak Ties versus Clustering
Conventional approaches recommend based on preferences of similar users
But, it is better to ask dissimilar people who bring a novel perspective
Define a form of controlled scattering
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

14. Link Analysis Web link: recommendation by page author
An external criterion for estimating the value of a page to others
Typically, web engines crawl the web, build giant indexes, and analyze links
Referral: dynamic, targeted recommendation by an agent
Similar mathematical concepts to above apply
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

15. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Chapter 20 Summary
Selection should be empirical: based on data
Centralized reputation mechanisms gather data but impose many restrictions
Social networks can avoid such limitations
Referrals help maintain distributed social networks
Social structure can evolve collaboratively
Services can be rated and selected and rated again, and so on …
Chapter 20
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns