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Publicações

Publicações por LIAAD

2008

Improving the performance of an incremental algorithm driven by error margins

Autores
del Campo Avilaa, J; Ramos Jimeneza, G; Gamab, J; Morales Buenoa, R;

Publicação
Intelligent Data Analysis

Abstract
Classification is a quite relevant task within data analysis field. This task is not a trivial task and different difficulties can arise depending on the nature of the problem. All these difficulties can become worse when the datasets are too large or when new information can arrive at any time. Incremental learning is an approach that can be used to deal with the classification task in these cases. It must alleviate, or solve, the problem of limited time and memory resources. One emergent approach uses concentration bounds to ensure that decisions are made when enough information supports them. IADEM is one of the most recent algorithms that use this approach. The aim of this paper is to improve the performance of this algorithm in different ways: simplifying the complexity of the induced models, adding the ability to deal with continuous data, improving the detection of noise, selecting new criteria for evolutionating the model, including the use of more powerful prediction techniques, etc. Besides these new properties, the new system, IADEM-2, preserves the ability to obtain a performance similar to standard learning algorithms independently of the datasets size and it can incorporate new information as the basic algorithm does: using short time per example.

2008

Schema matching on streams with accuracy guarantees

Autores
Gama, J; Aguilar Ruiz, J; Klinkenberg, R;

Publicação
Intelligent Data Analysis

Abstract
We address the problem of matching imperfectly documented schemas of data streams and large databases. Instance-level schema matching algorithms identify likely correspondences between attributes by quantifying the similarity of their corresponding values. However, exact calculation of these similarities requires processing of all database records - which is infeasible for data streams. We devise a fast matching algorithm that uses only a small sample of records, and is yet guaranteed to find a matching that is a close approximation of the matching that would be obtained if the entire stream were processed. The method can be applied to any given (combination of) similarity metrics that can be estimated from a sample with bounded error; we apply the algorithm to several metrics. We give a rigorous proof of the method's correctness and report on experiments using large databases.

2008

The dimension of ECOCs for multiclass classification problems

Autores
Pimenta, E; Gama, J; Carvalho, A;

Publicação
INTERNATIONAL JOURNAL ON ARTIFICIAL INTELLIGENCE TOOLS

Abstract
Several classification problems involve more than two classes. These problems are known as multiclass classification problems. One of the approaches to deal with multiclass problems is their decomposition into a set of binary problems. Recent work shows important advantages related with this approach. Several strategies have been proposed for this decomposition. The strategies most frequently used are All-vs-All, One-vs-All and Error Correction Output Codes (ECOC). ECOCs are based on binary words (codewords) and have been adapted to deal with multiclass problems. For such, they must comply with a number of specific constraints. Different dimensions may be adopted for the codewords for each number of classes in the problem. These dimensions grow exponentially with the number of classes present in a dataset. Two methods to choose the dimension of a ECOC, which assure a good trade-off between redundancy and error correction capacity, are proposed in this paper. The proposed methods are evaluated in a set of benchmark classification problems. Experimental results show that they are competitive with other multiclass decomposition methods.

2008

Special track on data streams

Autores
Gama, J; Carvalho, A; Aguilar Rlliz, J;

Publicação
Proceedings of the ACM Symposium on Applied Computing

Abstract

2008

Knowledge discovery from sensor data (SensorKDD)

Autores
Vatsavai, RR; Omitaomu, OA; Gama, J; Chawla, NV; Gaber, MM; Ganguly, AR;

Publicação
SIGKDD Explorations

Abstract

2008

RUSE-WARMR: Rule Selection for Classifier Induction in Multi-Relational Data-Sets

Autores
Ferreira, CA; Gama, J; Costa, VS;

Publicação
20TH IEEE INTERNATIONAL CONFERENCE ON TOOLS WITH ARTIFICIAL INTELLIGENCE, VOL 1, PROCEEDINGS

Abstract
One of the major challenges in knowledge discovery is how to extract meaningful and useful knowledge from the complex structured data that one finds in Scientific and Technological applications. One approach is to explore the logic relations in the database and using, say, an Inductive Logic Programming (ILP) algorithm find descriptive and expressive patterns. These patterns can then be used as features to characterize the target concept, The effectiveness of these algorithms depends both upon the algorithm we use to generate the patterns and upon the classifier Rule mining provides an excellent framework for efficiently mining the interesting patterns that are relevant. We propose a novel method to select discriminative patterns and evaluate the effectiveness of this method on a complex discovery application of practical interest.

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