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\markboth{Alberto H. F. Laender et al.}
{JIDM Editorial}


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\begin{center}{\LARGE {Editorial}}
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This new issue inaugurates the fourth volume of JIDM. Besides a new cover page, this issue brings two sections reflecting the JIDM aim of providing the Brazilian database community with a high-quality and dynamic publication venue.

The first section is dedicated to research groups and presents a single article. This article, entitled ``The Images and Data Bases Group at University of S\~{a}o Paulo" by Traina, Traina J\'{u}nior, Ciferri, Souza, Rodrigues J\'{u}nior and Cordeiro, features one of the most traditional and productive Brazilian database research groups.

The second section brings five articles that are extended and revised versions of selected short papers presented at SBBD 2012, the XXVII Brazilian Symposium on Databases held last October in S\~{a}o Paulo. The first article, by Gon\c{c}alves, Oliveira, Ocana, Ogasawara, Dias and Mattoso, is entitled ``Performance Analysis of Data Filtering in Scientific Workflows" and proposes an approach for improving the performance of parallel execution of scientific workflows by analyzing and filtering provenance data at run time. The second article, by Lima, Bai\~{a}o, Sampaio, Mattoso and Braganholo, is entitled ``Towards Recommendations for Horizontal XML Fragmentation" and proposes a set of guidelines for horizontal fragmentation of XML databases. The third article, by de Amo, Bueno, Alves and Silva, is entitled ``Mining User Contextual Preferences" and proposes a technique for mining contextual preferences expressed by a Bayasian Preference Network. The fourth article, by Guimar\~{a}es, Arcanjo, Antu\~{n}a, Moro and Ferreira, is entitled ``Processing XPath Structural Constraints on GPU" and shows how graphic cards can be leveraged to reduce the computational cost of processing an important subset of XQuery by proposing a new query evaluation algorithm designed to consider the cost model of GPUs. Finally, the fifth article, by Gomes, Oliveira, Almeida and Gon\c{c}alves, is entitled ``Is Learning to Rank Worth It? A Statistical Analysis of Learning to Rank Methods in the LETOR Benchmarks" and presents a detailed experimental analysis of several learning to rank methods over different datasets of the LETOR 3.0 and 4.0 benchmarks. All these articles describe ongoing work and have been selected by the SBBD 2012 program committee for their innovative ideas.

We would like to thank everybody who contributed to this edition of JIDM, particularly reviewers for their valuable comments and authors for the hard work in preparing their final manuscripts. 

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Alberto H. F. Laender\\
\indent \textit{Editor-in-Chief}

Vanessa Braganholo\\ 
\indent \textit{Associate Editor}

Renata Galante\\
\indent \textit{Short Papers Guest Editor}


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