Reference systems. The following is adapted from OpenGIS® Spatial Referencing by Coordinates (Topic 2) specification.

A reference system contains the metadata required to interpret spatial location information unambiguously. The description of an object's attributes can be done explicitly, by providing all defining parameters, or by identifier, a reference to a recognised source that contains a full description of the object. The {@link org.opengis.rs.Identifier} can be used to specify alternative names or aliases of the object defined.