Web Dynpro depends on the Model-View-Controller (MVC) principle. The Dynpro is divided into two parts: layout & flow logic, while the Web Dynpro is roughly divided into three layers, each of which can be developed and modified independently:
Presentation ( the view )
Interaction ( the controller )
Business data ( the model )
ABAP/Dynpro cannot really support a modern separation of front-end/presentation and backend/business logic; in fact they are working together as one object. Administration of Web Dynpro does not mean anything more than administration of the SAP Web Application Server and its also browser-based clients (zero footprint for UI). This means that many efforts for maintaining, and running different Web servers, UI servers, and client GUI installations which are the case in ABAP/Dynpro will simply go away. Since Web Dynpro is built on top of the SAP Web AS it offers the same support for multi-user development and software logistics that currently exist in R/3.
In the Web Dynpro the screen updates without page reloads. Also, the UI utilizes client-side dynamics, personalizes the browser and is 508-accessibility compliant. Web Dynpro supports reusing of components while in the Dynpro component reusing is very limited since the screen and the program are coupled (dealing with them as one object). In the Web Dynpro, User Interface will be dynamic from Client and server side but in the ABAP/Dynpro it will be dynamic from server-side only.
JAVA Development Infrastructure (JDI) is a new feature in SAP NetWeaver; Web Dynpro is built on it and JDI will connect Integrated Development Environment (IDE) to infrastructure. JDI will make further reductions in development time and costs, fixing bugs easily and increasing reliability for processes throughout the application life cycle.
JDI could be described by three elements which are: Design, Time, and Repository (DTR) which handles file versioning to ensure that all developers are working from the same set of codes; Component Build Service (CBS) which hosts all Java archives needed or produced during software development; and Software Logistics (SL) which is concerned in deploying the application in different systems and makes it available in all the stages of the product cycles and other transport and maintenance functions. Also, the developer can get an access to the JDI by importing a single development configuration file.
Finally, Web Dynpro is a revolution and leap in the UI development world and it will minimize the cost, time and effort in the cycles of training and implementation.