Web Dynpro (WD) is a proprietary web application technology developed by SAP AG that focuses on the development of server-side business applications. One of its main design features is that the user interface is defined in an entirely declarative manner. Web Dynpro applications can be developed using either a Java (Web Dynpro for Java, WDJ or WD4J) or ABAP (Web Dynpro ABAP,[1] WDA or WD4A) flavor. [source: Wikipedia]
