Polynomial space counting problems
SIAM Journal on Computing
Generalizations of Opt P to the polynomial hierarchy
Theoretical Computer Science
Qualifying answers according to user needs and preferences
Fundamenta Informaticae - Special issue: to the memory of Prof. Cecylia Rauszer
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Generalization and a Framework for Query Modification
Proceedings of the Sixth International Conference on Data Engineering
Supporting Incremental Join Queries on Ranked Inputs
Proceedings of the 27th International Conference on Very Large Data Bases
Multidimensional Recommender Systems: A Data Warehousing Approach
WELCOM '01 Proceedings of the Second International Workshop on Electronic Commerce
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Optimal aggregation algorithms for middleware
Journal of Computer and System Sciences - Special issu on PODS 2001
On the computational complexity of qualitative coalitional games
Artificial Intelligence
IEEE Transactions on Knowledge and Data Engineering
RankSQL: supporting ranking queries in relational database management systems
VLDB '05 Proceedings of the 31st international conference on Very large data bases
Relaxing join and selection queries
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Subtractive reductions and complete problems for counting complexity classes
Theoretical Computer Science - Mathematical foundations of computer science 2000
An incremental algorithm for computing ranked full disjunctions
Journal of Computer and System Sciences
Evaluating rank joins with optimal cost
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
A survey of top-k query processing techniques in relational database systems
ACM Computing Surveys (CSUR)
CARD: a decision-guidance framework and application for recommending composite alternatives
Proceedings of the 2008 ACM conference on Recommender systems
CARD: a decision-guidance framework and application for recommending composite alternatives
Proceedings of the 2008 ACM conference on Recommender systems
Ranking objects based on relationships and fixed associations
Proceedings of the 12th International Conference on Extending Database Technology: Advances in Database Technology
Finding a team of experts in social networks
Proceedings of the 15th ACM SIGKDD international conference on Knowledge discovery and data mining
FlexRecs: expressing and combining flexible recommendations
Proceedings of the 2009 ACM SIGMOD International Conference on Management of data
Group recommendation: semantics and efficiency
Proceedings of the VLDB Endowment
Breaking out of the box of recommendations: from items to packages
Proceedings of the fourth ACM conference on Recommender systems
Evaluating, combining and generalizing recommendations with prerequisites
CIKM '10 Proceedings of the 19th ACM international conference on Information and knowledge management
A survey on representation, composition and application of preferences in database systems
ACM Transactions on Database Systems (TODS)
Recommendation systems with complex constraints: A course recommendation perspective
ACM Transactions on Information Systems (TOIS)
On the complexity of query result diversification
Proceedings of the VLDB Endowment
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Recommendation systems aim to recommend items that are likely to be of interest to users. This paper investigates several issues fundamental to such systems. We model recommendation systems for packages of items. We use queries to specify multi-criteria for item selections and express compatibility constraints on items in a package, and use functions to compute the cost and usefulness of items to a user. We study recommendations of points of interest, to suggest top-k packages. We also investigate recommendations of top-k items, as a special case. In addition, when sensible suggestions cannot be found, we propose query relaxation recommendations to help users revise their selection criteria, or adjustment recommendations to guide vendors to modify their item collections. We identify several problems, to decide whether a set of packages makes a top-k recommendation, whether a rating bound is maximum for selecting top-k packages, whether we can relax the selection query to find packages that users want, and whether we can update a bounded number of items such that the users' requirements can be satisfied. We also study function problems for computing top-k packages, and counting problems to find how many packages meet the user's criteria. We establish the upper and lower bounds of these problems, all matching, for combined and data complexity. These results reveal the impact of variable sizes of packages, the presence of compatibility constraints, as well as a variety of query languages for specifying selection criteria and compatibility constraints, on the analyses of these problems.