Compared with texts, graphs are more intuitive to express comparative and structural information. Many graphical approaches, however, lack a formal basis for precise specifications in the design. This paper proposes a generative style-driven framework for software architecture specification based on a visual language formalism. In this framework, the designer uses graphical notations to define architectural styles. Given the graphical specifications, a visual language generator, i.e. a meta-tool, can automatically generate a specific design environment, which is suitable for the users without any knowledge of formal methods to directly manipulate software architectures by drawing box-line graphs. The graph transformation engine underlying the design environment can automatically validate structural integrity and reveal the hierarchical structure of a user-defined software architecture.