Ruby on Rails with Roles - Ein verteiltes Rollenmodell für RESTful Webservices

Roles are an important construct in conceptual modelling and object-oriented systsms. Concerning the World Wide Web role concepts did not attract much attention so far. However, especially in the World Wide Web there is a plethora of information, which could be better structured and be modelled more naturally if a role construct was available. In decentralized information systems, like the World Wide Web, role models have to fulfil additional requirements: Roles can be generated by generalization as well as by specialization, roles have to exist independently and can be integrated to a role hierarchy at any time, the navigation within a role hierarchy has to be supported to minimize access restrictions. A further requirement includes an uniform communication within an information system. Therefore URIs are best qualified for identification and XML for representation of roles. The main contribution of this thesis is an extension package for the web application framework Ruby on Rails that allows to work with role classes and instances within a web application. Ruby on Rails uses the model-view-controller architectural pattern (MVC) and provides for semi-automatic generation of model, view, controller and database table of a class by using a so-called scaffold generator. The role-extension package described in this thesis comes with a scaffold generator for role classes that intuitively integrates with the existing application framework. This extension package is developed in three steps. In the first step a prominent role concept will be implemented in the programming language Ruby. In the second step this implementation will be enhanced by requirements for its decentralized use, as described in the previous paragraph. In step three Ruby on Rails will be extended accordingly.