Resumo em Inglês:

Search operations in large sets of complex objects usually rely on similarity-based criteria, due to the lack of other general properties that could be used to compare the objects, such as the total order relationship, or even the equality relationship between pairs of objects, commonly used with data in numeric or short texts domains. Therefore, similarity between objects is the core criterion to compare complex objects. There are two basic operators for similarity queries: Range Query and k-Nearest Neighbors Query. Much research has been done to develop effective algorithms to implement them as standalone operations. However, algorithms to support these operators as parts of more complex expressions involving their composition were not developed yet. This paper presents two new algorithms specially designed to answer conjunctive and disjunctive operations involving the basic similarity criteria, providing also support for the manipulation of tie lists when the k-Nearest Neighbor query is involved. The new proposed algorithms were compared with the combinations of the basic algorithms, both in the sequential scan and in the Slim-tree metric access methods, measuring the number of disk accesses, the number of distance calculations, and wall-clock time. The experimental results show that the new algorithms have better performance than the composition of the two basic operators to answer complex similarity queries in all measured aspects, being up to 40 times faster than the composition of the basic algorithms. This is an essential point to enable the practical use of similarity operators in Relational Database Management Systems.

Resumo em Inglês:

Empirical studies have revealed that most users are dissatisfied with current help systems. One of the causes for many of the problems found in help systems is a lack of coupling between the process for creating online help and the human-computer interaction design of the application. In this paper, we present a method for building online help based on design models according to a Semiotic Engineering approach. We argue that there may be important benefits to the users if designers communicate their design vision, and we also point at the need to change current design practices to encourage creative and intelligent use of computer applications. We show how this proposal opens a direct communication channel from designers to users, and we hope this will contribute to introducing this new culture.

Resumo em Português:

A flexibilidade de modelos de autoria de alto nível (tais como o de SMIL 2.0) para a edição de Documentos Multimídia Interativos complexos pode levar os autores, em certos casos, a especificar relações de sincronização que não podem ser satisfeitas durante a apresentação do documento, caracterizando a ocorrência de inconsistências temporais. Por essa razão, é necessária a utilização de uma metodologia que ofereça uma semântica formal para o comportamento do documento, realize a verificação de consistência, o escalonamento e a apresentação levando em consideração o não-determinismo temporal desses documentos. Este artigo faz referência a uma metodologia para a concepção formal de Documentos Multimídia Interativos baseados na Técnica de Descrição Formal RT-LOTOS. Em particular, este artigo apresenta uma abordagem, utilizada pela nossa metodologia, para a tradução automática de documentos SMIL 2.0 em especificações RT-LOTOS.

Resumo em Inglês:

The flexibility of high level authoring models (such as SMIL 2.0) for the edition of complex Interactive Multimedia Documents can lead authors, in certain cases, to specify synchronization relations which could not be satisfied during the presentation of the document, thus characterizing the occurrence of temporal inconsistencies. For this reason, we need to apply a methodology which provides the formal semantics for the dynamic behaviour of the document, consistency checking, and the scheduling of the presentation taking into account the temporal non-determinism of these documents. This paper refers to a methodology for the formal design of Interactive Multimedia Documents based on the formal description technique RT-LOTOS. In particular, this paper presents an approach applied by our methodology for the automatic translation of SMIL 2.0 documents into RT-LOTOS specifications.

Resumo em Inglês:

We describe a new method for surface reconstruction and smoothing based on unorganized noisy point clouds without normals. The output of the method is a refined triangular mesh that approximates the original point cloud while preserving the salient features of the underlying surface. The method has five steps: noise removal, clustering, data reduction, initial reconstruction, and mesh refinement. We also present theoretical justifications for the heuristics used in the reconstruction step.

Resumo em Inglês:

The classic Douglas-Peucker line-simplification algorithm is recognized as the one that delivers the best perceptual representations of the original lines. It may, however, produce simplified polyline that is not topologically equivalent to the original one consisting of all vertex samples. On the basis of properties of the polyline hulls, Saalfeld devised a simple rule for detecting topological inconsistencies and proposed to solve them by carrying additional refinements. In this paper, we present an alternative form for the classic Douglas-Peucker to produce a simplified polyline which is homeomorphic to the original one. Our modified Douglas-Peucker algorithm is based on two propositions: (1) when an original polyline is star-shaped, its simplification from the Douglas-Peucker procedure cannot self-intersect; and (2) for any polyline, two of its star-shaped sub-polylines may only intersect if there is a vertex of one simplified sub-polyline inside the other's corresponding region.