It is well known that software evolution is an inescapable activity in the software lifecycle. In order to prevent the negative effects of this activity (decreased quality, increased complexity, etc.), some good practices have been recommended in the past. In this paper, we present a method which aims at automating a kind of assistance to software evolution. This assistance makes it possible to guide the developer when applying changes on a given software by making persistent some good practices, which can be considered as some kind of knowledge in the software engineering practice. In this method, a domain metamodel is firstly introduced. A set of constraints formalizing the good practices are then associated to this metamodel. Together, these two elements compose the basis upon which the automatic support for the evolution assistance has been built. 1

This Chapter describes how the design tool WebRatio (and its companion conceptual model WebML) have been extended to support the new requirements imposed by Rich Internet Applications (RIAs), that are recognized to be one of the main innovations that lead to the Web 2.0 revolution. Complex interactions such as drag and drop, dynamic resizing of visual components, graphical editing of objects, partial page refresh are addressed by the RIA extensions of WebRatio. The chapter discusses what kinds of modelling primitives are required for specifying such patterns and how these primitives can be integrated in a CASE tool. Finally, a real industrial case is presented in which the novel RIA features are successfully applied.