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Publications

Publications by HASLab

2011

Mining Association Rules for Label Ranking

Authors
de Sa, CR; Soares, C; Jorge, AM; Azevedo, P; Costa, J;

Publication
ADVANCES IN KNOWLEDGE DISCOVERY AND DATA MINING, PT II: 15TH PACIFIC-ASIA CONFERENCE, PAKDD 2011

Abstract
Recently, a number of learning algorithms have been adapted for label ranking, including instance-based and tree-based methods. In this paper, we propose an adaptation of association rules for label ranking. The adaptation, which is illustrated in this work with APRIORI Algorithm, essentially consists of using variations of the support and confidence measures based on ranking similarity functions that are suitable for label ranking. We also adapt the method to make a prediction from the possibly conflicting consequents of the rules that apply to an example. Despite having made our adaptation from a very simple variant of association rules for classification, the results clearly show that the method is making valid predictions. Additionally, they show that it competes well with state-of-the-art label ranking algorithms.

2011

Translating Alloy Specifications to UML Class Diagrams Annotated with OCL

Authors
Garis, AG; Cunha, A; Riesco, D;

Publication
Software Engineering and Formal Methods - 9th International Conference, SEFM 2011, Montevideo, Uruguay, November 14-18, 2011. Proceedings

Abstract
Model-Driven Engineering (MDE) is a Software Engineering approach based on model transformations at different abstraction levels. It prescribes the development of software by successively transforming models from abstract (specifications) to more concrete ones (code). Alloy is an increasingly popular lightweight formal specification language that supports automatic verification. Unfortunately, its widespread industrial adoption is hampered by the lack of an ecosystem of MDE tools, namely code generators. This paper presents a model transformation between Alloy and UML Class Diagrams annotated with OCL. The proposed transformation enables current UML-based tools to also be applied to Alloy specifications, thus unleashing its potential for MDE. © 2011 Springer-Verlag.

2011

Algebraic Specialization of Generic Functions for Recursive Types

Authors
Cunha, A; Pacheco, H;

Publication
Electr. Notes Theor. Comput. Sci.

Abstract
Defining functions over large, possibly recursive, data structures usually involves a lot of boilerplate. This code simply traverses non-interesting parts of the data, and rapidly becomes a maintainability problem. Many generic programming libraries have been proposed to address this issue. Most of them allow the user to specify the behavior just for the interesting bits of the structure, and provide traversal combinators to "scrap the boilerplate". The expressive power of these libraries usually comes at the cost of efficiency, since runtime checks are used to detect where to apply the type-specific behavior. In previous work we have developed an effective rewrite system for specialization and optimization of generic programs. In this paper we extend it to also cover recursive data types. The key idea is to specialize traversal combinators using well-known recursion patterns, such as folds or paramorphisms. These are ruled by a rich set of algebraic laws that enable aggressive optimizations. We present a type-safe encoding of this rewrite system in Haskell, based on recent language extensions such as type-indexed type families.

2011

Calculating with lenses: optimising bidirectional transformations

Authors
Pacheco, H; Cunha, A;

Publication
Proceedings of the 2011 ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation, PEPM 2011, Austin, TX, USA, January 24-25, 2011

Abstract
This paper presents an equational calculus to reason about bidirectional transformations specified in the point-free style. In particular, it focuses on the so-called lenses as a bidirectional idiom, and shows that many standard laws characterising point-free combinators and recursion patterns are also valid in that setting. A key result is that uniqueness also holds for bidirectional folds and unfolds, thus unleashing the power of fusion as a program optimisation technique. A rewriting system for automatic lens optimisation is also presented, to prove the usefulness of the proposed calculus. © 2011 ACM.

2011

Transformation of structure-shy programs with application to XPath queries and strategic functions

Authors
Cunha, A; Visser, J;

Publication
SCIENCE OF COMPUTER PROGRAMMING

Abstract
Various programming languages allow the construction of structure-shy programs. Such programs are defined generically for many different datatypes and only specify specific behavior for a few relevant subtypes. Typical examples are XML query languages that allow selection of subdocuments without exhaustively specifying intermediate element tags. Other examples are languages and libraries for polytypic or strategic functional programming and for adaptive object-oriented programming. In this paper, we present an algebraic approach to transformation of declarative structure-shy programs, in particular for strategic functions and XML queries. We formulate a rich set of algebraic laws, not just for transformation of structure-shy programs, but also for their conversion into structure-sensitive programs and vice versa. We show how subsets of these laws can be used to construct effective rewrite systems for specialization, generalization, and optimization of structure-shy programs. We present a type-safe encoding of these rewrite systems in Haskell which itself uses strategic functional programming techniques. We discuss the application of these rewrite systems for XPath query optimization and for query migration in the context of schema evolution.

2011

Integration of SIP protocol in Android Media Framework

Authors
Barbosa, A; Goncalves, J; Ribeiro, AN; Costa, A;

Publication
EUROCON 2011 - International Conference on Computer as a Tool - Joint with Conftele 2011

Abstract
The transmission of multimedia content between mobile devices is increasingly an area of exploration. The evolution of mobile devices and networks that support them, provide potential to create more sophisticated and innovating services. The fact that the Android platform does not provide the SIP protocol in its architecture, is a limiting factor for the development of new streaming applications. Throughout this paper the Android platform is presented, and more specifically the streaming protocols supported by the current streaming Media Framework. Based on the current Android Media Framework, this paper presents a possible architecture for the integration of the SIP protocol. The integration of this architecture is to surpass the limitations of the current Android platform and promote an improved performance in the current SIP applications, which is reflected in a lower power consumption of the device. © 2011 IEEE.

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