The present invention provides a method, data processing system and computer program product for providing a data stream transform service, for example for transforming a data stream into a format suitable for printing. A data-stream is divided into one or more work units, each work unit is provided to one or more transform engines to transform the work unit into the required format, and each transform engine is monitored whilst transforming a work unit. By monitoring each transform engine details of, for example, resource usage are obtained which may be used to calculate a fee to charge a client for performing transformation of a data stream, and/or failure of a transform engine can be detected and corrective action taken should a transform engine fail.