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

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

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

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

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

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

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

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

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

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

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

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

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

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

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