We present WildCAT, an extensible Java framework to ease the creation of context-aware applications. WildCAT provides a simple yet powerful dynamic model to represent an application's execution context. The context information can be accessed by application programmers through two complimentary interfaces: synchronous requests (pull mode) and asynchronous notifications (push mode). Internally, WildCAT is designed to support different kinds of extensions, from the simple configuration of the default generic implementation to completely new implementations tailored to specific needs. A given application can mix different implementations for different aspects of its context while only depending on WildCAT simple and unified API.