Applications on the Web are accessible for users withdifferent background, technicalenvironment used, political, social environment wherethey reside, interests, goals and so on. Thedifferent user types have slightly differentrequirements for features which such Webapplications shouldhave. The different requirements might be satisfiedby different variants of features maintained andprovided by Web applications. An adaptive Webapplication can be seen as a family of Webapplications where application instances are thosegenerated for particular user based on hischaracteristics relevant for a domain.In this book, we propose a new domain engineeringframework which extends a development process ofWeb applications with techniques required whendesigning such adaptive customizable Webapplications. Theframework is provided with design abstractions whichdeal separately with information served bythe Web application, environment used to deliver theinformation, and user characteristics which areobserved and used to constrain the information andthe environment selection.