A First Approach to Argument-based Recommender Systems based on Defeasible Logic Programming Carlos I. Chesñevar Dept. of Computer Science Universidad de Lleida - Spain Ana G. Maguitman Computer Science Dept. Indiana University – USA Guillermo R. Simari Dept. of Computer Science and Eng. Universidad Nacional del Sur – Argentina
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A First Approach to Argument-based Recommender Systems based on Defeasible Logic Programming
A First Approach to Argument-based Recommender Systems based on Defeasible Logic Programming. Outline. (1) Introduction and motivations. (2) Argumentation Framework DeLP. (3) Recommender Systems (RS). (4) Argument-Based RS. (5) An Argument-Based Search Engine. (6) Conclusions. Ongoing work. - PowerPoint PPT Presentation
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A First Approach to Argument-based Recommender Systems based on
Defeasible Logic Programming
Carlos I. ChesñevarDept. of Computer Science
Universidad de Lleida - Spain
Ana G. MaguitmanComputer Science Dept.
Indiana University – USA
Guillermo R. SimariDept. of Computer Science and Eng.
Universidad Nacional del Sur – Argentina
Outline
(3) Recommender Systems (RS)
(2) Argumentation Framework DeLP
(4) Argument-Based RS
(5) An Argument-Based Search Engine
(6) Conclusions. Ongoing work.
(1) Introduction and motivations
Recommender Systems address the problem of information overload by providing guidelines or hints.
The Problem: Information Overload
Limitations of Traditional Views
• Unable to perform qualitative inference on the recommendations.
• Unable to deal with the defeasible nature of user’s preferences.
• Unable to provide explanations: trustworthiness issues!
Our Proposal
• Integrate recommender system technologies with a defeasible argumentation framework.
• To enhance practical reasoning capabilities of current recommender systems
Outline
(3) Recommender Systems (RS)
(2) Argumentation Framework DeLP
(4) Argument-Based RS
(5) An Argument-Based Search Engine
(6) Conclusions. Ongoing work.
(1) Introduction and motivations
flies(X) bird(X), broken_wing(X)
flies(X) bird(X)
bird(X) penguin(X)
bird(opus)
broken_wing(opus)
(,)
bird(opus)
flies(opus)
, flies(opus)
={ flies(X) bird(X) }
Extension of logic programming which allows to reason with tentative, defeasible information.
Argument ,L 1) L 2) P, P3) There is no such that
satisfies 1) and 2).
DeLP (1)
bird(opus)
flies(opus)
bird(opus), broken_wing(opus)
flies(opus)
, flies(opus) , flies(opus)
Specificity is a syntax-based criterion used to define preference ( ) among arguments.
An argument , L defeats another argument , Q if
, L is in conflict with , Q
, Q is preferred over , L or is unrelated to , L
DeLP (2)
U
UD
D
D
U
UD
L
An argument , L is warranted if the root of the associated tree is labelled as U.
In order to determine whether an argument , L is finally acceptable, a dialectical tree rooted in , L can be built.
Leaves are U-nodes.
Inner node U iff every children node is a D-node.
Inner node D iff at least one children node is a U-node.
DeLP (3)
How DeLP works
DeLP Interpreter
Abstract Machine
?- flies(opus)
• YES, there exists a warranted argument , L )
• NO, there exists a warranted argument for , L
• UNDECIDED, none of the above cases hold.
Possible Answers to Query L
User Query Defeasible rules
Strict rules
Facts
DeLP Program P
Outline
(3) Recommender Systems (RS)
(2) Argumentation Framework DeLP
(4) Argument-Based RS
(5) An Argument-Based Search Engine
(6) Conclusions. Ongoing work.
(1) Introduction and motivations
Recommender Systems
Programs that create a model of the user’s preferences, or the user’s task, to help identify worthwhile items such as news, web pages, books, etc.
Goals for Recommender Systems
• Find what the user wants.
• Know what the user likes.
• Gain trustworthiness from the user.
Traditional Approaches
Collaborative Filtering Recommenders: Infer preferences of individual users based on behavior of multiple users.
Content-Based Recommenders: Infer preferences of individual users based on what the user liked in the past.
Hybrid Recommenders: Combine both.
Hybrid RS: outline
Outline
(3) Recommender Systems (RS)
(2) Argumentation Framework DeLP
(4) Argument-Based RS
(5) An Argument-Based Search Engine
(6) Conclusions. Ongoing work.
(1) Introduction and motivations
Argument-based RS
Model the users’ preference criteria in terms of a DeLP program built on top of a content-based search engine.
Users’ preference criteria are:
• Incomplete
• Potentially Inconsistent
Encoding Users’ Preferences
DeLP
Program
user: preferences and behavior of active user (facts, strict rules and defeasible rules)
pool: preferences and behavior from a pool of users (defeasible rules)
domain: domain background knowledge (facts, strict rules and defeasible rules)
Argument-Based RS Architecture
Prioritizing Recommendations
Recommendations can be prioritized according to their epistemic status:
• Sw warranted results
• Su undecided results
• Sd defeated results.
Outline
(3) Recommender Systems (RS)
(2) Argumentation Framework DeLP
(4) Argument-Based RS
(5) An Argument-Based Search Engine
(6) Conclusions. Ongoing work.
(1) Introduction and motivations
Argument-Based Search Engine
A Case-Study: Solving Web Search Queries
Consider a journalist who wants to search for news articles about recent outbreaks of bird flu.
Outbreaks of bird flu
?
Querying a Conventional Search Engine
news regarding
bird flu
Too many results!
Applying Implicit KnowledgeArticles written by Bob Beak are reliable.Usually, if the journalist is trustworthy then the article is reliable.
Old articles are not reliable.If a journalist never faked a report then she is reliably.
Thailandian and Japanese newspapers usually offer a biased viewpoint on bird flu outbreaks.The “Japanese Times” is non biased.Chin Yao Lin faked a report.