IT is difficult to see where Hitachi Data Systems (HDS) placed its top priority when designing its new open systems ''road map'' for the future it announced last week. The company talked about the so-called Osiris programme as a strategy for customers making an orderly transition from its IBM-compatible mainframe platform to standards-based open systems computing. But Osiris is also HDS's own long-term survival strategy - mapping its own transition from proprietary mainframe to open platforms. Shrinking demand and squeezed profit margins on its IBM-compatible mainframe product lines have hurt sales. Osiris appears an acknowledgement not just of the changing role of mainframe computing, but its ultimate extinction as well. The Osiris programme sets out to design a ''confluence'' of proprietary mainframe and open systems platforms'', according to HDS open systems marketing director Mr Richard Otto. The programme is made up of a series of software and hardware products that let the customer link open systems-based local area networks (LANs) to their installed mainframe environment. The mainframe, with ''partitioning'' built into the operating system that allowed it to act as a database serving both proprietary and open environment, then became a giant network file server capable of delivering terrabytes of on-line data to end-users, Mr Otto said. The first product launched under Osiris is a mainframe-based SuperServer which combines an operating system based on the Open Software Foundations OSF/1 and a RISC-(reduced-instruction-set computing) based network co-processor which provides the physical interface to LANs.