||The web is more and more used as a platform for full-fledged, increasingly complexapplications, where a huge amount of change-intensive data is managed by underlyingdatabase systems. From a software engineering point of view, the development of webapplications requires proper modelling methods in order to ensure architectural correctnessand maintainability. Existing modelling methods for web applications, however, fall shorton considering a major requirement posed on today's web applications, namelycustomisation. Web applications should be customisable with respect to various contextfactors comprising different user preferences, device capabilities and locations in mobilescenarios, to mention just a few.The goal of this diploma thesis is to realise a modelling method for this kind of applicationsbased on the Unified Modelling Language (UML). This modelling method called WUML(Web-Unified Modelling Language), should cover all modelling dimensions of webapplications, comprising levels in terms of content, hyperbase and presentation, aspectscharacterised by structure and behaviour and phases, i.e. analysis, design andimplementation. Proper modelling elements are provided to cope with the requirement ofcustomisation which is considered as influencing these dimensions. Finally the WUMLnotation is integrated in a commercial UML CASE tool.