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7 results on '"HALLEZ, AXEL"'

2. Fuzzy and uncertain spatio-temporal database models : a constraint-based approach

Author

Guy De Tré, Caluwe, Rita, Hallez, Axel, and Verstraete, Jörg

Subjects
object-oriented database model, Technology and Engineering, Spatio-temporal information modelling, constraints
Abstract

In this paper a constraint-based generalised object-oriented database model is adapted to manage spatiotemporal information. This adaptation is based on the definition of a new data type, which is suited to handle both temporal and spatial information. Generalised constraints are used to describe spatio-temporal data, to enforce integrity rules on databases, to specify the formal semantics of a database scheme and to impose selection criteria for information retrieval.

Published
2002

3. Adapting TIN layers to represent fuzzy geographic information

Author

Verstraete, Jörg, De Tré, Guy, Hallez, Axel, De Baets, Bernard, Fodor, Janus, and Pasi, Gabrialla

Subjects
Science General
Abstract

One of the latest research topics in geographic information systems (GIS for short) is the modeling of fuzzy (imprecise or vague) and/or uncertain information. A GIS usually contains large amounts of data and requires very specific operations to manage (geographic) data, both of which are described in a geographic database model. In this paper, the basic concepts for a data model describing the structure of and operations on fuzzy or uncertain geographic information are presented. Specific for the presented model is the adaptation of triangulated irregular networks (TINs), commonly used in GIS (e.g. to model altitudes), for the modelling of fuzzy (geographic) data.

Published
2002

6. A possibilistic view on set and multiset comparison.

Author

Bronselaer, Antoon, Hallez, Axel, and De Tré, Guy

Subjects
ALGORITHMS, CONSTANTS of integration, AGGREGATION operators, OPERATOR-valued measures, RELATIONAL databases, DATABASES, SECONDARY analysis
Abstract

Comparative evaluation operators for sets and multisets are proposed from a possibilistic point of view. In general, an evaluator estimates the possibility of (non) co-reference of two arbitrary (sub)-objects. Such operators can be used in a hierarchical possibilistic framework for finding co-referent objects with a complex structure. This paper first discusses properties of evaluators in general and continues with studying operators for sets and multisets, thereby making a clear distinction between hard and soft evaluators. Hard evaluators are based on evaluation of derived (multi)sets, while soft evaluators use a low level evaluator to incorporate co-reference at element level. The two important parts of such a soft evaluator are an injective element mapping and an aggregation function. An algorithm to provide the injective mapping is presented and discussed. For the aggregation step, ordered weighted conjunction is studied by introducing parameterized fuzzy quantifiers to calculate weight vectors. An advanced learning strategy is introduced to train the optimal parameter matrix. [ABSTRACT FROM AUTHOR]

Published
2009

7. Contourline based modelling of vague regions

Author

Hallez, Axel, Verstraete, Jörg, Guy De Tré, and Caluwe, Rita

Subjects
spatial data, vague regions, Science General
Abstract

This paper introduced a model based on contour lines to represent a vague region modeled as a fuzzy set. The model allows the user to adjust the accuracy of the membership function to the needs of the application and can enforce the continuity of this function whenever desirable.

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