VISCO
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Abstract
Fig. 1: The Graphical Query Editor
Fig. 2: The Map Viewer
Fig. 3: The Query Result Inspector
At VL '97, we presented the first design of the visual (sketch-based) spatial query language VISCO. VISCO is a visual spatial query system designed for extracting information from spatial information systems (SIS, especially GIS) in a visual way. VISCO supports the retrieval of interesting constellations of spatial objects (from spatial information systems) based on their structural, topological, metric and geometric attributes and relationships between them. The term spatial information system refers to a broad class of systems which collect, manage and offer the analysis and presentation of spatial data (e.g. lakes, roads, and buildings in a GIS).
The language is based on a strong naive physics metaphor for query objects (e.g. marbles, nails, rubberbands) and assumes a topologically structured vector representation of the data of interest. Data models like the one assumed here can be found in advanced vector-based GIS (in contrast to raster-based GIS). The data in vector-based systems usually consists of nodes or vertices (points), edges (lines) and faces (simple polygons). In VISCO, nails and marbles represent point objects, various types of telescope antennas and beams represent simple segments (with arbitray, given maximal or given minimal or exact length), and rubberbands represent arbitrary polylines (see examples below). Polygons, polylines and aggregates can be constructed bottom up from these elements. A transparency film represents a transformable aggregate (of the already mentioned objects) with a local coordinate system. Transparency films can be translated, rotated, scaled, and stacked upon like layers. Each geometric object (except transparency films) must be defined on exactly one transparency film (the so-called carrier). Special constraints regarding scalability and rotatability of films can be established (e.g., a film is defined as unscalable and has an extension of 100 x 100 meters or may be scaled only proportionally, etc.).
Fig. 4: Architecture of the VISCO-System
The VISCO prototype consists of three main components:
Another component of the system is the optimizing visual language query compiler.- the graphical query editor offering "sketch"-based querying of spatial databases (see Fig. 1),
- and a powerful map-inspection tool (Map Viewer) for the spatial database (see Fig. 2), and
- a browser-like query-result inspector (see Fig. 3).
