Domains
A domain is a set of possible values of a variable. In ILWIS, a domain is the set of possible IDs, class names, or values that can be used for instance in a map. All maps, tables and columns (data objects) have a domain; a domain is a service object for maps, tables and columns. One domain can be used for several data objects.
The four main types of domains are:
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for data objects that contain unique identifiers (e.g. plot 1024, plot 1025) |
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for data objects that contain classes (e.g. soil units: clay, sandy loam) |
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for data objects that contain measured, calculated or interpolated values (e.g. height, concentration) |
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for satellite images containing values between 0 and 255. |
Maps which use a class, value or the Image domain can have a user-defined representation.