wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (04/21/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Tuesday, April 25, 1989
Mr. D.P. Mulders, Graduate Student, Department of
Computer Science, University of Waterloo will speak on
``Network Security: A Review of Measures and
Mechanics.''
TIME: 2:30 PM
ROOM: DC 1302
ABSTRACT
As a growing number of users rely on transferring
critical data over computer networks, the need for
correct network security becomes more apparent. This
paper outlines possible threats presented by an
arbitrary network malcontent, and then discusses
necessary goals of network security aimed at
counteracting these threats. Measures for realising a
secure network and their corresponding mechanisms are
placed within the OSI architectural framework and
examined in depth.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (04/22/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Monday, April 24, 1989
Mr. Paul Cormier, graduate student, Dept. of Computer
Science, University of Waterloo will present a Master's
Essay Presentation on ``Shoshin''.
TIME: 2:30 PM
ROOM: DC 1304
ABSTRACT
Shoshin is a distributed software testbed supporting
interprocess communication through message-passing
primitives. It is based on a loosely coupled system in
which messages are sent between Micro- Vax II machines
via an Ethernet network. Recently, Shoshin was
modified to support tightly coupled processors, in
which it is possible to have more than one processor
per Shoshin node. It was decided that an identical,
trusted kernel would run on each processor in the
multiprocessor node. In addition, the kernel would
have to be modified to support semi-local interprocess
communication, that is, message passing between
processes on different processors, but within the same
multiprocessor node.
In this talk we present the Shoshin distributed
operating system, its purpose and its usage. The
primary and secondary bootstrap operations performed by
the master and auxiliary processors are examined. This
also includes some of the hardware limitations imposed
on this design as a result of the MicroVax II
architecture. The primitives supported by the Shoshin
kernel to provide local and remote interprocess
communication are examined and help us to derive the
design alternatives considered for semi-local inter-
processor communication. The advantages and
disadvantages of each design are presented along with
the design chosen and the algorithms used to implement
this design.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (04/26/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Friday, April 28, 1989
Lori M. Murphy, graduate student, Dept. of Computer Science, University of
Waterloo will speak on "Equation Solving Using an L1 Minimization Technique"
TIME: 2:30 PM
ROOM: DC 1302
ABSTRACT
Many algorithms have been proposed for solving
systems of nonlinear equations. This paper
examines the L1 minimization technique designed by
Bartels and Conn (and extended by Busovaca to handle
degeneracy) and investigates its use as a nonlinear
system solver. The performance of the algorithm is
compared to such traditional methods as Brown's
algorithm and Powell's Hybrid algorithm.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (07/06/89)
Dept. of Computer Science, University of Waterloo, will speak on
``General Purpose and Binary Image Data Compression.''
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION SEMINAR
-Friday, July 7, l989
Mr. Roland Olsson, graduate student, Dept. of Computer
Science, University of Waterloo, will speak on
``General Purpose and Binary Image Data Compression''
TIME: 1:30 p.m.
ROOM: DC 1304
ABSTRACT
Data is described by a model that computes the
probabilty p of the next input symbol, which is
optimally coded using -log2 p bits. The predictions of
the model are used by a Huffman or an arithmetic coding
algorithm. Techniques based on the latter yield the
smallest compressed file size.
Lempel-Ziv compression algorithms are often faster, but
do not give quite as good compression. A novel Lempel-
Ziv variant is developed.
Binary image compression can be used in for example
facsimile machines and image databases. Run-length
coding, READ coding and pel colour prediction using a
template are reviewed. A new way of encoding an image
as a set of contours and contour locations is discussed
in detail. The last method considered uses character
recognition to achieve very high compression for binary
images that mainly consist of text."wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (07/28/89)
Dept. of Computer Science, will speak on
``Diambiguation Using the New Oxford English Dictionary.''
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Wednesday, August 2, 1989
Mr. Byron Weber Becker, graduate student, Dept. of
Computer Science, will speak on ``Disambiguation Using
the New Oxford English Dictionary.''
TIME: 2:00 p.m.
ROOM: DC 1304
ABSTRACT
One of the basic activities in communication is
distinguishing which of several meanings for a given
word is the intended meaning. In a dictionary, these
meanings are listed as different "senses."
If a computer could perform this sense disambiguation
auto- matically, it could prove useful in applications
such as automatic translation and indexing newspaper
articles.
I have been investigating using the New Oxford English
Dictionary for sense disambiguation. I will be
reviewing similar work done by M. Lesk and K.S. Jones,
as well as my own approach. Comparisons between the
approaches as well as ideas for future research will be
presented.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (08/03/89)
Dept. of Computer Science, University of Waterloo,
will speak on ``A Graph Package for MAPLE.''
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Thursday, August 10, 1989
Mr. David Clark, graduate student, Dept. of Computer
Science, will speak on ``A Graph Package For MAPLE.''
TIME: 3:30 p.m.
ROOM: DC 1304
ABSTRACT
This talk describes the implementation of a package for
working with graphs under Maple. The packages allows
the user to construct, manipulate, and test properties
of graphs. The package is intended for students and
researchers in mathematics interested in manipulating
small graphs. The package solves the basic
representation issues and provides enough functionality
for beginning users.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (08/11/89)
Dept. of Computer Science, will speak on
`` A Processing Model for Redirection Clues in Discourse.''
DEPARTMENT OF COMPUTER SCIENCE UNIVERSITY OF WATERLOO SEMINAR
ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Thursday, August 17, 1989
Mr. David Hsu, graduate student, Dept. of Computer Science,
will speak on ``A Processing Model for Redirection Clues in
Discourse.''
TIME: 11:00 a.m.
ROOM: DC 3540
ABSTRACT
This essay examines the processing of interruptions in discourse
based on the model proposed by Grosz and Sidner. Three
types of interruptions with redirection clue words or phrases
are proposed in the Grosz and Sidner model - flashbacks,
digressions and semantic returns. We develop an interruption
processing model (IPM) and present an implementation, which
takes as input discourse that includes interruptions and
produces as output an interpretation of the structure of that
discourse. The design of algorithms for the processing model is
guided by the high-level mechanisms suggested by Grosz and
Sidner. The algorithms present low-level descriptions of the
updates required for the representation of the discourse, as
stored in the intentional structure and attentional state.
Several examples are provided to illustrate the structures of
discourse at any given instance. The examples also help to
explain the behavior of clues in discourse.
The processing model also forms part of the realization of the
computational argument analysis system by R. Cohen. Together
with the implementation of connective clues by T. Smedley,
they establish the clue interpreter in the system.
Together with the implementation of Evidence Oracle by M.
Young, they constitute the processing model for the system.wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (11/23/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Friday, December 1, 1989
Mr. F.K.T. Sun, graduate student, Dept. of Computer
Science, will speak on ``Using X11 to display visual
effects.''
TIME: 2:30 p.m.
ROOM: DC 1331
ABSTRACT
We describe six demonstration programs for displaying
variants of effects reported in the vision literature.
The demonstrations use a windowed workstation
environment, the X Window System Version 11 (X11). The
perfomance of the window system is analyzed in terms of
our implementation experience and suggestions are made
for future window system architectures based on our
experience. The visual effects are discussed in terms
of what they teach about the display of information
within a windowed environment and the tools that the
visual effects themselves provide for improving that
environment.
November 23, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/01/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Wednesday, December 6, 1989
Mr. A. Scian, graduate student, Dept. of Computer
Science, will speak on ``Software Reusability
Paradigms''.
TIME: 1:30 p.m.
ROOM: DC 1331
ABSTRACT
Building upon the ideas and work of others to construct
something new and unique is a common theme in our
world. Unfortunately, this ideal is not practised when
it comes to developing software. The idea of software
reusability is to develop software without reinventing
the wheel each time. The problems associated with
software construction will be examined along with a
study of other fields that deal with complexity. The
similarities and differences regarding the way
complexity problems are handled gives rise to a set of
requirements for software reusability. A broad survey
of current research in software reusability will
highlight the progress in different areas. In
addition, major attempts at reusing software will be
studied in depth.
The attempts at software reusability will be contrasted
against the set of requirements for software
reusability. The prospects for software reusability
look good in the immediate future and it is hoped the
benefits can be realized by the software community.
November 30, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/08/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Monday, December 11, 1989
Mr. Frank Miller, graduate student, Dept. of Computer
Science, will speak on ``Mapping SQL/W Into Request
Trees.''
TIME: 11:00 a.m.
ROOM: DC 3540
ABSTRACT
SQL/W is the query language for the LauRel database
system, a new DBMS being developed at the University of
Waterloo. LauRel and SQL/W are based on an extended
relational model with facilities to handle nested
relations and reference attributes. This talk will
describe how an SQL/W query is transformed into a
request-oriented tree which will serve as a basis for
the execution plan. The request tree will be a binary
tree of nodes which store information regarding the
steps necessary to evaluate the query. This request
tree will be passed through the query optimizer and
then to the execution engine which will convert the
tree into an execution plan.
December 7, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/08/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Tuesday, December 12, 1989
Mr. T. Cifelli, graduate student, Dept. of Computer
Science, will speak on ``A Multicast Communication
Protocol for Shoshin.''
TIME: 2:30 p.m.
ROOM: DC 1304
ABSTRACT
This presentation suggests a design for efficient
1-to-N Inter-Process Communication (IPC) for Shoshin.
The programming entities of client, server, and peer
have been generalized to be one or more processes.
They may be organized into groups and addressed with a
single group identifier (GID) as targets for the
multicast IPC. The nsend primitive has been added to
the IPC repertoire and allows application processes to
send messages to either individual processes or process
groups. The existing brecany primitive is used to
receive messages sent using nsend. The nsend primitive
does not provide the same reliability guarantees as the
existing bsend primitive, which only allows sending to
indiviual processes. The 1-to-N IPC covers three
communication domains: processors within a
multiprocessor, Ethernet LAN, and the Campus Internet.
December 7, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/14/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Monday, December 18, 1989
Mr. Alfredo Viola, graduate student, Dept. of Comp.
Sci., will speak on ``Design and Implementation of an
Algebra of Data Structures.''
TIME: 3:30 p.m.
ROOM: DC 1331
ABSTRACT
"At most points in a program one in concerned solely
with the behavioural characteristics of a data
structure. One is interested in what one can do with
it, not in how the various operations on it are
implemented" (J.V. Guttag, 1977).
We define the algebra by presenting the Abstract Data
Types which specify the data structures we consider. We
will present a hierarchy in which the relationships
among the Abstract Data Types are explicitly expressed.
We implement this algebra using the system package
Gauss developed by Michael B. Monagan at the University
of Waterloo using the Maple programming language. This
package defines a hierarchy of algebraic structures. It
has system primitives which allow the implementation of
abstract data types exploiting the notions of category
and multiple inheritance.
The result is a very compact implementation in which we
have achieved a high degree of abstraction where the
algebraic properties of the data structures are
presented explicitly.
December 13, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/15/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Tuesday, December 19, 1989
Mr. Marc Lavergne, graduate student, Dept. of Comp.
Sci., will speak on ``A Study of Distributed Election Protocols.''
TIME: 1:30 p.m.
ROOM: DC 1331
Election is a fundamental problem of distributed computing. Many
problems in distributed systems exhibit the behaviour of election
or can be solved by means of election. Processor and communication
failures complicate the election process. Several issues have to
be considered when designing election protocols under these types
of failures.
This talk presents several election protocols from the literature
which address such failures. The different approaches used to handle
failures and related problems are discussed. Alternative
approaches to some of the problems are then presented.
Although extensive work has been done on election protocols,
much of the work assumes an underlying network topology, usually
ring-based networks or complete networks. Elections in these
specific distributed environments are NOT considered. wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/16/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Wednesday, December 20, 1989 (NOTE DATE!!)
Mr. Allan Wong, graduate student, Dept. of Computer
Science will speak on ``User-Level Shared Memory for
Shoshin.''
TIME: 9:30 a.m.
ROOM: DC 1331
ABSTRACT
Shoshin is a distributed software testbed supporting
interprocess communication through message-passing
primitives. It is based on a loosely coupled system in
which messages are sent between MicroVAX II machines
via an Ethernet network. Recently, Shoshin was
modified to support tightly coupled processors, in
which it is possible to have more than one processor
per Shoshin node. In addition to local memory for
each processor, global memory can be made accessible to
every processor in the same node. To make effective
use of this global memory, a set of shared memory
primitives has been designed and implemented to allow
this global memory to be shared by user processes in
the same Shoshin node.
We begin this talk by outlining the structure of the
Shoshin distributed operating system, its purpose
and its usage. A selection of previous work on
shared memory is described. Then the shared memory
primitives designed for Shoshin are presented. This is
followed by a discussion of the advantages and
disadvantages of some of the implementation
alternatives. An application program designed to
utilize the primitives is illustrated and performance
results for it are examined.
December 14, 1989wlrush@water.waterloo.edu (Wenchantress Wench Wendall) (12/19/89)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
MASTER'S ESSAY PRESENTATION
-Thursday, December 21, 1989
Mr. Debasish Jana, graduate student, Dept. of Computer
Science will speak on ``Synchronous Communication and
Static Process Structure - Problems and a Proposed
Solution.''
TIME: 2:30 p.m.
ROOM: DC 1331
ABSTRACT
A programming language for distributed system
environment has to choose a set of communication
primitives(synchronous or asynchronous) and a
structure of processes(static or dynamic).
In a client-server model, a client requests for service
from a server and the server, in turn, requests several
resources for their availabilities. A server encounters
a local delay when a local resource needed is not
available and it encounters a remote delay when the
server makes a call to another module which is busy or
has to perform considerable computing before making a
response. Remote delays are mainly because of
communication or I/O delays. Liskov et al argued that
the combination of static process structure and
synchronous communication has adequate expressive power
for handling local delays. But, it is not entirely
suitable for dealing with remote delays. They also
suggested that a distributed programming language
should abandon either synchronous communication or
static process structure.
In this essay, we propose a new facility, a
communication primitive reply-with that shows Liskov et
al's hypothesis is not entirely true. This new
primitive largely removes the limitations of
synchronous communication primitives in combination
with static process structure, when combined with send,
receive, reply (Thoth's message passing primitives) and
also with other facilities e.g. Ada rendezvous,
December 13, 1989
- 2 -
monitors.
December 13, 1989