Value :: evaluate - Refresh attribute value

Generic attributes with data source definition are evaluated once, when accessing the value for an instance the first time. Until changing the selection for the owning parent property handle, the value is not evaluated, again. This may cause problems, when changing attribute values in the instance, on which the transient attribute value depends. In order to re-evaluate the attribute value, evaluate() may be called. The function also calls the doAfterRead() event handler in order to activate application event handler to update the attribute value.

When the attribute is not transient, the function does not have any effect. When the value is not accessible, the function throws an error.