Definition of dependent data objects

The definition of a dependent data object, which is the result of a calculation or another operation, stores the complete expression by which the dependent data object was created. The definition thus defines how a dependent map, table or column was created. The definition of a dependent data object is shown in the properties of an object.

A dependent data object can easily be recalculated when it is not up-to-date anymore when input data have changed; ILWIS can simply execute the definition again. When the definition is a MapCalc or TabCalc formula, you can even change the expression itself.

The definition of dependent maps and tables is stored in the map's or table's object definition file. In principle, only the object definition files are stored on disk; data files are calculated when a dependent map or table is displayed. For dependent columns, the definition is stored in the object definition file of the table to which the column belongs.