A wide range of computationally intensive applications such as information retrieval, on-line analytical processing and data mining inherently require concurrency, because concurrent data maintenance, query processing and multi-user operation are functional requirements. Therefore, concurrent programming is a prerequisite for such systems. However, existing tools for parallel programming fail to meet these demands for concurrency and the adoption of parallel processing for these application domains is thus hindered. In this paper, we discuss the use of threads and concurrent programming constructs in the state of the art in parallel programming tools and environments. We find that the necessary functionality is available, but often in an inconvenient and unreliable manner. Due to the fact that the programmability and maintainability of parallel programs is a major concern, we consider the existing solutions inadequate or insufficient. We argue that an additional layer of middleware for threads and inter-thread communication and synchronization is necessary to support the effective development of persistently deployed parallel services for our targeted application domain and present the MPI Threads (MPIT) interface specification. We give several real-world examples to demonstrate its use and present performance benchmarks to illustrate the cost of the additional layer of indirection.