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
|| 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 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.
|| They includes intervals that are used to dived range of values.
|| They contains unique identifiers associated with items in a data objects (e.g. plot 1024, plot 1025). They simply contain strings as items.
|| 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.
|| 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.
|| 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.