Data elements in the toolkit can be typed, which means that they know the type of business object they represent. Examples of business objects are Money, Date, ProductNumber, and CorrespondenceAddress. Data Elements that are type-aware know the business rules they should exhibit. For example, they know how to format themselves for display and perform any required validation when they are requested to change their value. They also know how to clone themselves, and they contain some status information flags that are updated by the application during its life cycle.

This functional information provided by the operation runtime model (the context hierarchy) is used by the JSP tags to render a business field as an HTML visual control. The JSP tags may exploit the model information, which may indicate whether a field is mandatory, if it is a read-only field, if it is in error, and what validation script is associated with the field. Most tags only use a subset of these properties. If a property is requested by the tag and this property is not defined, then the tag assumes the following default values: