The present invention extends to methods, systems, and computer program products for compile time interpretation of markup codes. Embodiments of the invention can be used to specify custom behaviors to be taken in response to any of a number of ways that markup codes (e.g., XML data) can be constructed and in response to any number of ways that markup codes can be accessed. At compile time, the construction of objects and/or the modes of access for objects using mark up codes are known. As such, the compiler, type-system and development environment can use a known set of custom behaviors to regulate or give feedback on what constructions or modes of access are allowed, and what their characteristics are.