mwang@watmath.UUCP (mwang) (11/20/85)
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- Tuesday, November 12, 1985.
Prof. S. Christodoulakis of this department will speak on ``Optical
Disks in Office Automation and their Retrieval Performance''.
TTIIMMEE:: 12:30 PM
RROOOOMM:: MC 5158
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Optical disks started appearing in the computer market.
It is projected that they will compete favorably with
magnetic storage media in many demanding applications
like office filing and engineering data bases. In this
talk we outline the projected long term difficulties
between magnetic and optical disks and we describe some
properties of optical disks that make them appropriate
for these markets.
Based on our description we present a model for study-
ing the performance of retrieval operations from opti-
cal disks. We then describe a simple optical disk head
scheduling algorithm and we present exact and approxi-
mate analytic formulae for the evaluation of the re-
trieval cost for documents and records from an optical
disk. Finally we outline some research directions in
the area.mwang@watmath.UUCP (mwang) (11/21/85)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
ESSAY PRESENTATION
- Monday, November 25, 1985.
Mr. Michael Wright, a graduate student of this depart-
ment, will speak on ``Backward Error Recovery in a UNIX
Environment''.
TIME: 3:30 PM
ROOM: MC 6091A
ABSTRACT
Backward error recovery is an important technique for
recovery in software systems that are designed to func-
tion as specified, even in the presence of unforeseen
errors caused by design faults or faults in the
environment. The presentation will begin with a gen-
eral discussion of backward error recovery and its
variants, including both inclusive and disjoint mul-
tilevel recovery.
The provision of backward error recovery has been
incorporated into IOSYS, an entension of the UNIX sys-
tem interface that provides a simple file and record
management system for experimentation with data struc-
tures. The recovery facility is quite flexible, sup-
porting both inclusive and disjoint recovery. A pro-
gram using disjoint recovery can supply its own
recovery routines. Since a program also has full con-
trol over recovery regions (which need not be nested),
this provides a most general tool for experimentation
with backward error recovery. A description of the
facility, with some implementation details and measure-
ments of its efficiency, will be given.