This paper shows how XML can be used for static and dynamic analysis of architectures. Our analysis 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 provides a formal approach to the design of architectural description languages and a general mathematical foundation for the use of formal methods in enterprise architectures. For dynamic analysis we define transformations of models of architectures, modeled in XML, and for this purpose the XML vocabulary for an architecture is extended with a few constructs defined in the Rule Markup Language (RML). There are RML tools available that perform the desired transformations.