Programming Notes for Web Dynpro Programming Interface
The user interface elements specified by SAP are sufficient for developing many of the user interfaces for Web applications. They ensure the user sees a standardized screen. However, not all user interfaces are displayed equally in the same format, which means some dynamic programming is required.
No functions are permitted to be used that are provided in the SWDP package interface. You can find all released obects in the SWDP package interface in the system. These are usually classes that begin with CL_WD_, and interfaces that start with IF_WD_.
Classes that begin with CL_WDR_ and interfaces that begin with IF_WDR_ are not allowed to be used. These classes are not contained in the package interface and they can change without prior notice. Furthermore, there may be side effects from calling these internal class methods. There are some exceptions to this rule, for instance, CL_WDR_VIEW_ELEMENT.
If you are unsure whether a class or interface has been released, you can define a package usage relationship from your package to the package interface SWDP, and activate server and client checks for your package. The extended syntax check then indicates whether you are allowed to use a certain object or not.
Classes provided by Web Dynpro are not permitted to inherit, and interfaces are not permitted to be implemented, unless permission is explicitly mentioned in the documentation.