FOSS4G 2008
Glossary
Submitted by admin on Sat, 2006-12-09 01:40.
- Feature Schema
- A set of classes and their corresponding properties and relationships. Each Feature Schema typically contains the classes for a specific domain, for example, Electrical Schema, Gas Schema, etc. The Feature Schema defines its classes in an FDO provider-independent form.
- GML
- OGC´s Geography Markup Language. An XML format for geographic data.
- Schema
- In RDBMS terms, a Schema is a collection of tables, indexes, views, etc. in a database. Feature and RDBMS schemas do not correspond 1:1. A Feature Schema may be stored in different RDBMS schemas and an RDBMS schema might be composed of multiple logical schemas.
- OGC
- Open GIS Consortium
- Schema Mapping
- A set of hints that determine how Feature Schemas are stored in an FDO data store. The contents of Schema Mappings vary depending on the FDO Provider type.
- Tolerance
- Used to determine when two points are close enough to be considered to be equivalent in certain spatial tests. In FDO, the tolerance value is used as a radius around a position rather than as a distance along an axis. In the majority of cases, the distance between the points is compared to the tolerance using the 'less than' predicate. If the X and Y tolerances are both 0.05, the point B (1.0, 1.0) is considered to be equivalent to point A (0.96, 0.96) and point C (1.04, 1.04), but is not considered to be equivalent to point D (0.96, 0.94) or point E (1.04, 1.06). The relationship is not transitive. That is, point A is not equivalent to point C. Repeated applications of the isEquivalentTo predicate to the same data always yields the same result.