One of the most important topics in parallel application development is portability. No standard parallel computational model exists, whereas the multitude of different parallel architectures, programming paradigms and methodologies introduces significant difficulty in developing multi-system parallel applications. In this paper we present a platform-based architecture for developing portable parallel applications through the use of the platform approach. A platform is built on top of the native operating systems offering a common application programming interface (API). The API consists of a set of primitives through which portable applications can be developed (since only the platform - not the applications - requires re-programming for porting to different architectures). Furthermore, we define a set of key primitives specifically designed for implementing database applications. Our work towards this direction has been triggered by our recent implementation experience on parallel platforms and our interest in developing a parallel database system.