A framework for open, dynamic, and reflective applications contains high level metadata that define blocks of composable elements using a service definition, which defines specific keys for using the block of code. The service definition may be exported from the code using reflection without having to load the code into memory, and decisions on which block of code and how to load the code may be made at runtime. The composable elements may be grouped into composable parts. Composable part definitions may be used to instantiate or produce composable parts. At runtime, dynamic applications may search from many composable elements, and instantiate and execute the composable element as part of the application.