Domain unit example

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Configuration examples Domain unit/Table

Contents

Introduction

The one-dimensional (table) domain unit corresponds to what in a database usually is called a table. The domain unit unit defines the table and the number (cardinality) and order of entries. Attributes of this table have the configured unit as domain unit.

Configuration

Domain units can be configured in a GeoDMS configuration in three ways:

Explicitly configuring the cardinality and order in the configuration

Example

unit<uint8> direction: nrofrows = 4
{
   attribute<string> name  : ['North','East','South','West'];
   attribute<string> label   := Name;
}

In this example the domain unit direction is configured with 4 entries (rows).

  • The attribute name is used to name each entry in the table (it is advised to use name for an attribute, of which the values can be used as tree item names, see also naming conventions) .
  • An attribute with as name: label is configured. This is advised, as these labels are presented every time the id of the domain or a relation towards this domain is requested in a table. The label is presented after each index numbers between normal brackets. The labels are not copied to the clipboard or exported.

For domain units with a small number of elements, this way of configuring is fine. If the number of entries/rows and/or attributes increases, a configuration for a more user friendly way of editing the data is presented in the: tabular data paragraph of the page: configuration files as data source.

Deriving the cardinality and order with an expression

Example

unit<uint32> region := unique(GridDomain/regioncode);  

In this example the domain unit region is derived from the unique occurrences of the regioncode attribute of a GridDomain domain unit.

We advice to use the unique function mainly to explore your dataset. If the set of entries of a domain is known, configure this set explicitly (example 1). This make the configuration less dependent on the occurrences of (all) values in your data and the indexing persistent.

Except from the unique function, domain units are also often defined with the subset, combine or union_unit functions.

Deriving the cardinality and order from a storage

Example

unit<uint32> region
: StorageName = "%SourceDataProjDir%/region.shp"
, StorageType   = "gdal.vect";

In this example the cardinality and order of the values in the domain unit are derived from the region Shapefile.

If source data is read from a storage, this is the advised way of configuring the domain.

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