107,040 research outputs found
Optimal Information Retrieval with Complex Utility Functions
Existing retrieval models all attempt to optimize one single utility function, which is often based on the topical relevance of a document with respect to a query. In real applications, retrieval involves more complex utility functions that may involve preferences on several different dimensions. In this paper, we present a general optimization framework for retrieval with complex utility functions. A query language is designed according to this framework to enable users to submit complex queries. We propose an efficient algorithm for retrieval with complex utility functions based on the a-priori algorithm. As a case study, we apply our algorithm to a complex utility retrieval problem in distributed IR. Experiment results show that our algorithm allows for flexible tradeoff between multiple retrieval criteria. Finally, we study the efficiency issue of our algorithm on simulated data
Flexible constrained sampling with guarantees for pattern mining
Pattern sampling has been proposed as a potential solution to the infamous
pattern explosion. Instead of enumerating all patterns that satisfy the
constraints, individual patterns are sampled proportional to a given quality
measure. Several sampling algorithms have been proposed, but each of them has
its limitations when it comes to 1) flexibility in terms of quality measures
and constraints that can be used, and/or 2) guarantees with respect to sampling
accuracy. We therefore present Flexics, the first flexible pattern sampler that
supports a broad class of quality measures and constraints, while providing
strong guarantees regarding sampling accuracy. To achieve this, we leverage the
perspective on pattern mining as a constraint satisfaction problem and build
upon the latest advances in sampling solutions in SAT as well as existing
pattern mining algorithms. Furthermore, the proposed algorithm is applicable to
a variety of pattern languages, which allows us to introduce and tackle the
novel task of sampling sets of patterns. We introduce and empirically evaluate
two variants of Flexics: 1) a generic variant that addresses the well-known
itemset sampling task and the novel pattern set sampling task as well as a wide
range of expressive constraints within these tasks, and 2) a specialized
variant that exploits existing frequent itemset techniques to achieve
substantial speed-ups. Experiments show that Flexics is both accurate and
efficient, making it a useful tool for pattern-based data exploration.Comment: Accepted for publication in Data Mining & Knowledge Discovery journal
(ECML/PKDD 2017 journal track
Problem-Solving Knowledge Mining from Usersâ\ud Actions in an Intelligent Tutoring System
In an intelligent tutoring system (ITS), the domain expert should provide\ud
relevant domain knowledge to the tutor so that it will be able to guide the\ud
learner during problem solving. However, in several domains, this knowledge is\ud
not predetermined and should be captured or learned from expert users as well as\ud
intermediate and novice users. Our hypothesis is that, knowledge discovery (KD)\ud
techniques can help to build this domain intelligence in ITS. This paper proposes\ud
a framework to capture problem-solving knowledge using a promising approach\ud
of data and knowledge discovery based on a combination of sequential pattern\ud
mining and association rules discovery techniques. The framework has been implemented\ud
and is used to discover new meta knowledge and rules in a given domain\ud
which then extend domain knowledge and serve as problem space allowing\ud
the intelligent tutoring system to guide learners in problem-solving situations.\ud
Preliminary experiments have been conducted using the framework as an alternative\ud
to a path-planning problem solver in CanadarmTutor
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