This paper describes and reports on the use of an environment, called Agora, that supports the construction of large, computationally expensive and loosely-structured systems, e.g. knowledge-based systems for speech and vision understanding. Agora can be customized to support the programming model that is more suitable for a given application. Agora has been designed explicitly to support multiple languages and highly parallel computations. Systems built with Agora can be executed on a number of general purpose and custom multiprocessor architectures.