Many software systems are mixed-language systems today, i.e., they bind together components defined in different programming and specification languages. Analyses and refactorings implemented in current software development tools, e.g., integrated development environments (IDEs), cannot process these mixed-language systems as a whole since they are too closely related to particular programming languages and do not process mixed-language systems across language boundaries. In this paper, we discuss the foundations of cross-language analysis and refactoring. We propose a meta-model for capturing relevant information in a language independent way and an architecture for integrating language specific front-ends, and analysisand refactoring-components. As a proof of concept, we introduce X-DEVELOP, an IDE implementing the ideas discussed for a number of languages, analyses, and refactorings. Based on our contributions, cross-language software development tools are constructible in a straightforward way delivering the same productivity as today?s single language tools.