We describe the creation of a development framework for a platform-based design approach, in the context of the SegBus platform. The work intends to provide automated procedures for platform build-up and application mapping. The solution is based on a model-based process and heavily employs the UML. We develop a Domain Specific Language to support the platform modeling. An emulator is consequently introduced to allow an as much as possible accurate performance estimation of the solution, at high abstraction levels. Automated execution schedule generation is also featured. The resulting framework is applied to build actual design solutions for a MP3-decoder application.