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

Chapter 202Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Reputation Mechanisms 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 (typically a number and text) How to aggregate them How to decay them over time Owns ratings – controls how it can be used

Chapter 203Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Recommender Techniques Content-based filtering Social information filtering Collaborative filtering Model-based approaches Memory-based approaches Use ratings directly to recommend

Chapter 204Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Recommending Products vs. Services Products (by a product vendor) The recommender is the provider Votes are known to recommender Votes are given 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 can occur but not known to registry

Referrals

Chapter 206Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Social Networks and Referral Chains Referral chains provide: Way to judge the quality of an expert's advice Reason for the expert to respond in a trustworthy manner Social networks induce referral chains in which an individual may participate As the chains get longer The trustworthiness of a recommendation decreases The effort to find experts increases Therefore, shorter chains are better

Chapter 207Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Service Communities Each principal Provides services 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 contact lists Deciding whom to contact for a service

Chapter 208Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Distributed Treatment of Referrals Receive request Model asker Respond Ask Follow referrals Use Rate; update

Chapter 209Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Model for Referrals Each agent has An interest (services sought) An expertise (services provided) Models of acquaintances Acquaintance models are built autonomously and represent Acquaintances’ expertise (ability to provide good service along a set of dimensions) Sociability (ability to provide accurate referrals)

Chapter 2010Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Reputation Buildup and Collapse A participant who begins to misbehave is detected

Social Mechanism for trust

Chapter 2012Service-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 2013Service-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 participate in different subcommunities Shortcuts: weak ties

Chapter 2014Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Quality Relates Inversely to Clustering

Chapter 2015Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Weak Ties versus Clustering Conventional approaches give recommendations based on the preferences of similar users (as discussed previously) For finding the best referrals, it is best to ask dissimilar people who bring a novel perspective Define a form of controlled scattering

Chapter 2016Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Link Analysis Links on a web page correspond to recommendations by the page author Links provide an external criterion for estimating the value of a page (as opposed to words on a page, which can be rigged) Typically, web engines crawl the web, build giant indexes, and analyze links A referral corresponds to a targeted recommendation by an agent. While we may not crawl referrals ahead of time, the same mathematical concepts apply

Chapter 2017Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Social Mechanism of trust Using probabilistic models for reasoning with beliefs Bayesian model Primarily using conditional probabilities Dempster-Shafer model Model that explicitly deals with belief values for various hypothesis

Chapter 2018Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Identity & Reputation Approaches to service selections based on reputations – face the threat that such reputations can be forged Also, vendors can change names easily – “cheap pseudonyms”

Chapter 2019Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter Reputation Mechanisms Recommender Techniques Referrals Social Mechanism for Trust Identity