LegendBurster adopts a knowledge-engineering approach to managing GIS information, and this requires the explicit development of an ontology for each LegendBurster project.
Knowledge bases are at the heart of knowledge engineering, and these are described in the Appendix to this HELP documentation. Since ontologies lie at the heart of most knowledge bases, the Appendix also includes an introduction to ontologies.
Depending on the context, a class may have a physical expression as a collection of things which have certain attributes in common, or it may have an abstract expression as the actual specification of the "classifying" attributes.
An instance is something that exists, and may belong to any number of classes, depending on the definitions of the classes, and the attributes of the instance.
In LegendBurster, we regard mapObjects (points, lines or polygons) as instances, and we regard queries as classes.
Entities are things - that may be physical or abstract. Entities have attributes and values for these attributes.
In LegendBurster, both mapObjects and queries are entities.
Proceed to Negation and Frequencies