Community Research and Development Information Service - CORDIS

Spatial data revision and constraint-propagation consistency restoration

The quality of the geographic information is difficult to assess unless being confronted to the real world. At least it is sometimes possible to check the validity of several data sets respectively to each other, when explicit constraints are available. Logical consistency can be therefore a very valuable source of quality assessment. Several situations of spatial propagation of constraints have been studied, and a general canvass is proposed to handle them with several techniques (described through other individual results).

The balance is between: either an appropriate and specific representation allowing efficient algorithms, or a more general representation with hardly tractable algorithms.
(1) If the spatial propagation is "linear", then it is possible to design some ad-hoc representations with linear-time algorithms. It has been applied to the analysis of a flooding described by incomplete and imprecise information: we have been able to detect conflicts and to propose solutions that restore the overall data consistency. It has been applied to the monitoring of a fleet (in Town), also with incomplete information: we have been able to alert about possibly blocking segments in a street graph. (cf. result about logic of linear constraints)
(2) if the constraints are more complex, it is still possible to represent them with data, but the tractability of the algorithms is rapidly an issue. We have develop two approaches relevant for spatial data: a) the use of local containment restrictions (the opposite of the "butterfly effect") when some semantics is available (maximal extension of some phenomenon, etc.), or b) the use of random stratification (cf. result about S-models).

Finally, this general approach can be used in a range of geographical application and can be integrated in a mediation scenario, where a front-end helps a user to check if his needs and the available data are in one of the tractable configurations, and to run it. A demonstrator has been coded and will be release by the end of the project. The code will be available for future implementation.

Reported by

Universite de Provence
CMI, 39 rue Joliot-Curie
13453 Marseille
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