In this paper we introduce a logical viewpoint on architectures. The logical viewpoint is based on the distinction between symbolic and semantic models of architectures. The core of a symbolic model consists of its signature that specifies symbolically its structural elements and their relationships. A semantic model is defined as a formal interpretation of the symbolic model. This leads to more precise characterization of the concepts introduced in IEEE standard 1471-2000, and provides a formal approach to the design of enterprise of architectural description languages and a general mathematical foundation for the use of formal methods in enterprise architectures. Additionally, we show how this logical viewpoint allows for the definition of a simple general XML language for the description of both static and dynamic aspects of an architecture. For the meta-analysis of both these aspects we introduce a new XML tool for general XML transformations based on a Rule Markup Language.