The goal of the thesis is to solve the task of defining a flexible query language for distributed structured and semistructured data and to implement this language. For example, data can be represented as HTML files in the file system, whereby an XML document contains metadata about these files. Hence, these two data sources have to be merged appropriately. In order to satisfy the needs of the heterogeneous group of users, a flexible adaptable query language is required. Therefore a query model is developed which serves as a basis for an abstract syntax for query languages; this abstract syntax can be translated in concrete textual as well as graphical query languages. An implementation of the ideas proposed in the thesis is done in the area of virtual courses, especially in the project ”Virtual University of Applied Sciences”.