Digital, maker of one of the most popular hardware platforms for library automation, has moved to retain customers who may be considering Unix over its proprietary VMS operating system. VMS will be rewritten to conform to the Portable Operating Standard Interface (POSIX) in order to achieve interoperability among VMS, DOS, ULTRIX (Digital's Unix implementation), and other versions of Unix. The five-year plan is intended to offer the best of both worlds: VMS performance and security, and Unix's networking.