Spatial Reference System skos:definition issue #879

The skos:definition for Spatial Reference System is "A Reference System that describes a set of standards for uniquely identifying the position of an entity or the direction of a vector within a defined spatial region by means of measurements along one or more Coordinate System Axes."

However, child classes define reference systems which do not use "measurements along one or more coordinate system axes", i.e., both the geospatial coordinate and spherical coordinate systems are angular measurements. Furthermore, there are many other spatial reference systems in mathematics which do not use axes, such as the general curvilinear set which includes ellipsoidal, toroidal, and others.

Suggest shortening the definition to "A Reference System that describes a set of instructions for uniquely identifying the position of an entity within a defined spatial region". Note the change from "standards" to "instructions". Also not sure if uniqueness is true for all Reference systems, for example lat, lon = (0,180) is the same as (0, -180), same point two different ways of stating the coordinate (yes, I understand the coordinate system may want to put limits, i.e., -180<lon<=180, but some reference systems may want to count the number of times around (windings) in which case one point in the spatial region will have multiple coordinate values). So could change "uniquely" to "precisely" or eliminate this word too.

(I also wonder if Spatial Reference Systems are really Directive ICEs instead of Descriptive, i.e., instructions for how to get to a coordinate from another coordinate (e.g., the origin)) - but this is another topic of discussion).