Service objects: Domain

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Domain Representation Georeference Coordinate system
Domain

A Domain is a service object that contains information used by e.g., a map, a column, an attribute table, by other service object such as representation, etc. In ILWIS all the maps, columns, attribute tables need a domain. In addition, a domain may also provide a link to a default representation, so that the colors for the map values or thematic classes are known. There are various types of domain that can be assigned to ILWIS data objects namely:

Domain Types Description
Numeric Numeric domains are used for data object which contain measured, calculated or interpolated values (e.g. height, concentration). Numeric domains are defined by a numeric range, consisting of a start and an end value and a resolution. The resolution defines the step size in the range.
Item Item Domains in general contains a range that made up of several items. These items can be of different forms such as thematic items, named items or interval items.
Numeric Item They are pretty similar to Numeric domains with a maximum, minimum and resolution while also carrying a name for each item. Such a domain can be assigned to map representing e.g., vegetation zones to certain heights.
Interval They includes intervals that are used to dived range of values.
Identifier They contains unique identifiers associated with items in a data objects (e.g. plot 1024, plot 1025). They simply contain strings as items.
Thematic The Thematic domains consist of items including its name, code and description. They are used to associate and represent data objects classes e.g., soil units, vegetation types, land use, etc.
Time The Time domains wrap a certain period of time including starting and ending. Usually, the spatial time series data, e.g., satellite imageries, is a sequence that taken at successive equally spaced points in time.
Time interval They includes the interval between the time data to represent a series of data indexed in time order.
Color The Color domain is used for raster maps which contain merely colors (Red, Green, Blue); the pixels have no meaning e.g. color composites.
Color pallet They consist of two colors, which mark the beginning and ending of the range.

The following are example of other available domain:
Bit; is a system domain available for raster maps and columns that have to store values 0 and 1.
Bool; domain used for data objects which contain only 2 classes or values (e.g. True and False) and undefined values. Available as system domain Bool and system domain YesNo , but you can also create your own Boolean domains.
Byte; is a system domain for images in which you wish to regard 0 as undefined.
String; is a system domain available for columns that contain text.
None; system domain None is available for tables in which the records do not store information on a map.
Binary; is a system domain for internal use only.
Distance; is a system domain for the output map of the Distance operation.
Count; is system domain
Min1to1; is a system domain,
NILto1; is a system domain
Perc; is a system domain
FlowDirection; is a system domain for the output map of the Flow Direction operation.