The Vuel Concept: Towards a new way to manage Multiple Representations in Spatial Databases ISPRS / ICA Workshop Multi-Scale Representations of Spatial Data Ottawa July 7 th, 2002 Eveline Bernier, M.Sc. Yvan Bédard, Ph.D.

Presentation Outline  The context : MOD and SOLAP  The nature of the Multiple Representations  The Vuel concept  The SOLAP prototype  Conclusion

Map-On-Demand  Maps are created upon a set of constraints defined by the user.  The user can select the scale and the themes to be displayed.  On the web, the map must be displayed as fast as possible (< 10 sec.).

Spatial On-Line Analytical Processing (SOLAP)  A visual platform built especially to support rapid and easy spatio-temporal analysis and exploration of data.  No query language.  Based on a multidimensional structure.  Operations such as drill-down, drill-up and drill- across.

SOLAP Operation Drill-Down

Several Display Modes

Problematic   There is a need, for both applications, to display a same reality according to different points of view and differents abstraction levels. On-the-Fly generalization not efficient enough to supports such applications Existing MR structures don’t support all kinds of multiplicity (geometric, semantic and graphic) and are multi-scale only.

Multiplicities Multi-ScaleSingle-Scale Geometric Graphic Semantic View B View A View C View X View Y E View X View Y View A View B View A Building View B House View X View Y Assessment Parcel Cadastral Parcel

Proposed Solution  To develop a new approach that extends multiple representation concepts for added flexibility in spatial databases.  This structure should support different geometric, semantic or graphic representations for the same element of the reality, according to different or similar granularities.

The VUEL   an idea [Bédard et al., 2000]: influenced by multidimensional data structures; aimed at supporting spatial multidimensional applications (e.g. SOLAP). (View Element) What it is:  the visible part of a view. VUEL Geometric Graphic Semantic  a unique combinaison of semantic, geometric and graphic occurrence relations.

The Vuel Ground Reality Building View 4 VUEL 4 House View 1 VUEL 1 House View 2 VUEL 2 Building View 3 VUEL 3 Geometric Graphic Semantic VUEL

The Vuel Conceptual Model  Built with UML and based on a multidimensional database paradigm.  The vuel is presented as a central table linking three dimensions: semantic, geometric, graphic.  A spatial database view (e.g. a map) becomes an aggregation of vuels.

Visual Basic SOLAP Prototype Implementation

SOLAP Interface DEMO

Conclusion  The conceptual model can be implemented on an existing relational plateform.  The VUEL concept is a flexible database view engine and represents a new solution to manage multiple representations because it supports simultaneously geometric multiplicity, semantic multiplicity and graphical multiplicity.  Supports different combinations of geometry, semantic and graphic semiology.  This structure allows a user to easily navigate between all the multiplicities, at the occurrence level as well as at the class level.

Future Works  Continue the development of the SOLAP application based on the vuel structure; Add new functionalities, temporal aspect, other display modes, implementation on a «real» multidimensional structure, etc.  Develop a web-based system that supports maps-on demand; SQL-Server (VUEL) – Geomedia WebMap – ASP.  Add generalization functionalities; Based on a pattern approach.

Thanks! Questions??????