2.3.6   Fields

The fields in ERE define data that is used when evaluating selection trees. The fields available to a selection tree are specified in the associated service.

There are two types of field definitions.

• Data field - A field that is defined with data type and parameter type. The parameter type defines if the field is used to store values, or provide values for other fields. The definition may either be set in the service, called a Service Defined Field (SDF), or in the selection tree, called a Tree Defined Field (TDF).
• Hierarchical field - A field with a hierarchical structure. The structure must end with at least one data field. All data fields within a hierarchical field structure must consist of the same parameter type, see Section 5.3.6.1.

Fields can be defined to contain collections of representative data or grouped together with other fields. This makes handling data easier and more structured.

For more details on the different fields, see Section 5.3.2.