Model driven development is gaining momentum, and thus, larger and more complex systems are being represented and developed with the help of modeling. Complex systems often suffer from a number of problems such as difficulties in keeping the model understandable, long compilation times and high coupling. With modeling comes the possibility to validate the models against constraints, which makes it possible to handle problems that traditional static analysis tools can't solve. This thesis is a study on to what degree the usage of automatic model validation can be a useful tool in addressing some of the problems that appear in the development of complex systems. This is done by compiling a list of validation constraints based on existing problems, implementing and applying fixes for these and measuring how a number of different aspects of the model is affected. After applying the fixes and measuring the impact on the models ,it could be seen that validation of dependencies can have a signicant impact on the models by reducing build times of the generated code. Other types of validation constraints require further study to decide what impact they might have on model quality.

The subject matter of this project is accessibility of web pages and possibilities of its automated validation. This thesis defines what web accessibility really is and identifies what disabilities can users of the Internet suffer from. The main goal is to analyse and to compare current web accessibility rules valid in the USA, in the European Union and in the Czech Republic and to research existing validators as well. The tools are divided into the following categories: Online tools, toolbars and desktop applications. The output of this project is in form of specification and implementation of a new validation tool.