Model-based approaches in development are widely recognized as a potential way of increasing productivity in software engineering. Model-based development is driven by model transformations. There is a demand for researching the ways how model transformation can become more flexible, efficient, and highly-configurable as well as validated. This thesis addresses issues of visually defined validated model transformations. The first contribution deals with the relationship between the pre- and postconditions and the Object Constraint Language (OCL) constraints enlisted in model transformation rules. This construct provides the background of an online validated transformation approach. The second result group provides an aspect-oriented constraint management approach to solve the problem of the crosscutting constraints. This method facilitates consistent constraint management in model transformation rules, furthermore, it makes the constraints as well as the transformation rules reusable. The third contribution includes the realization a visual control flow language (VCFL).