cheriton@SU-PESCADERO.ARPA (David Cheriton) (02/25/86)
From: David Cheriton <cheriton@su-pescadero.arpa> PERSISTENT OBJECT SYSTEM FOR SYMBOLIC COMPUTERS Satishe Thatte Texas Instruments Thurs. Feb 27th at 4:15 pm. MJH 352 (Part of Distributed Systems Group Project meeting) The advent of automatically managed, garbage-collected virtual memory was crucial to the development of today's symbolic processing. No analogous capability has yet been developed in the domain of "persistent" objects managed by a file system or database. As a consequence, the programmer is forced to flatten rich structures of objects resident in virtual memory before the objects can be stored in a file system or conventional database. This task puts a great burden on the programmer and adversely affects system performance. A persistent object system that extends the automatic storage management concepts of a symbolic computer to the domain of persistent objects will be presented. The system supports long-term, reliable retention of richly structured objects in virtual memory itself, without resorting to a file system. Therefore, the system requires a crash recovery scheme at the level of virtual memory. The persistent object system is based on a uniform memory abstraction, which eliminates the distinction between transient objects (data structures) and persistent objects (files and databases), and therefore, allows the same set of powerful and flexible operations with equal efficiency on both transient and persistent objects from a programming language such as Lisp or Prolog, without requiring a special-purpose database language. It is expected that the exploitation of such a capability will lead to significant breakthroughs in knowledge/data base management.