2001 Technical Reports | SCS | UW
[Please remove <h1>]
CS-2001-26 |
Title |
Finding Hidden Independent
Sets in Interval Graphs |
Authors |
T. Biedl, B. Brejova, E. D. Demaine, A. M. Hamel, A. Lopez-Ortiz,
T. Vinar |
Abstract |
We design efficient competitive algorithms for discovering information
hidden by an adversary. Specifically, consider a game in a given
interval graph $G$ in which the adversary chooses an independent set
$X$ in $G$. Our goal is to discover this hidden independent set $X$
by making the fewest queries of the form ``Is point $p$ covered by an
interval in $X$?'' Our interest in this problem stems from two
applications: experimental gene discovery with PCR technology and the
game of Battleship (in a 1-dimensional setting). We provide adaptive
algorithms for both the verification scenario (given an independent
set, is it $X$?) and the discovery scenario (find $X$ without any
information). Under some assumptions on the interval graph, these
algorithms use an asymptotically optimal number of queries in every
instance. |
Date |
December 2001 |
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CS-2001-25 |
Title |
A Direct Algorithm to Constract the Minimal Telescopers for
Rational Functions (q-Difference Case)
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Authors |
H.Q. Le, S.A. Abramov
and K.O. Geddes |
Abstract |
In this paper we present
a direct algorithm to construct the minimal telescopers for rational functions
for the q-difference case.
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Date |
November 2001 |
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CS-2001-24 |
Title |
HypergeometricSum: A Maple Package for Finding Closed Forms
of Indefinite and Definite Sums of Hypergeometric Type |
Authors |
H.Q. Le, S.A. Abramov
and K.O. Geddes |
Abstract |
We describe the Maple module HypergeometricSum which
provides various tools for finding closed forms of
indefinite and definite sums of hypergeometric type,
and for certifying a large class of combinatorial
identities. The document is intended both as an
an elementary introduction to the subject and as a
reference manual for the module. |
Date |
November 2001 |
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CS-2001-23 |
Authors |
L. Stanchev |
Abstract |
In this paper we introduce bag relational algebra with aggregation over
a particular representation of incomplete information called c-tables.
The c-table representation is an extension of the Codd relational model
with richer semantics for null values. The reason c-tables were chosen
for our exploration is that they are the least expressive relational representation
of incomplete information over which relational algebra is closed and
can be "well defined". We justify the need for duplicate preserving relational
algebra over this representation of incomplete information by introducing
aggregation over c-tables with duplicates.
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Date |
October 2001 |
Comments |
This report was generated
as part of a project for a 700 level course at the University of Waterloo,
Waterloo, ON, Canada |
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CS-2001-22 |
Title |
Evolution of Recurrent Neural Networks to Control Autonomous
Life Agents |
Authors |
T. Abou-Assaleh |
Abstract |
Studies of artificial life (alife) attempt to simulate simple living
beings. On the other hand, autonomous agents researchers are interested
in building agents that are able to complete a particular task without
supervision. In this research, these two areas of artificial intelligence
are combined together into what we call "Autonomous Life Agent"
(ALA). ALA is an artificial agent that is sent to some environment to
live in without any supervision or any predefined behaviour rules. The
primary goal of the agent is to learn how to survive in the artificial
environment it lives in. In this research, we utilize a recurrent neural
network to determine the agent's actions. A novel ALA Training System
was developed that evolves recurrent neural networks using genetic algorithms.
The resulting agents are capable of living in multiple similar worlds
starting from random initial positions as well as in worlds that are unseen
during the training.
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Date |
October 2001 |
Comments |
Source code of the ALA Training System is available upon request.
Appears in:
Tony Abou-Assaleh, Jianna Zhang, and Nick Cercone. 2001. "Evolution of
Recurrent Neural Networks to Control Autonomous Life Agents." Proceedings
of the Genetic and Evolutionary Computation Conference, GECCO-2001. San
Francisco, CA: Morgan Kaufmann Publishers. Page 903.
Please direct all comments and suggestions to the author
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CS-2001-21 |
Authors |
A. Lopez-Ortiz |
Date |
October 2001 |
Report |
Only available in printed format |
CS-2001-20 |
Authors |
A. Lopez-Ortiz |
Date |
October 2001 |
Report |
Only available in printed format |
CS-2001-19 |
Authors |
P.A.S. Ward |
Date |
#issued July 4, 2001, |
Report |
Only available in printed format |
CS-2001-18 |
Title |
A Behavioral Analysis Approach to Pattern-Based Composition |
Authors |
Jing Dong, Paulo S.C. Alencar and Donald D. Cowan |
Date |
June 2001 |
Report |
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CS-2001-17 |
Title |
User's Manual as a Requirements
Specification |
Authors |
D.M. Berry, K. Daudjee,
J. Dong, M.A. Nelson and T.Nelson |
Date |
May 2001 |
Report |
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CS-2001-16 |
Authors |
D. Toman |
Date |
# issued May 16th |
Report |
Only available in printed format |
CS-2001-15 |
Title |
Finding Shortest Paths
in Large Network Systems |
Authors |
E.P.F. Chan and N. Zhang |
Date |
May 2001 |
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CS-2001-14 |
Title |
Optimal Arrangement of
Leaves in the Tree Representing Hierarchical Custering of Gene Expression
Data |
Authors |
T. Biedl, B. Brejova,
E.D. Demaine, A.M. Hamel and T. Vinar |
Abstract |
In this paper, we study how to present gene expression data to display
similarities by trying to find a linear ordering of genes such that genes
with similar expression profiles will be close in this ordering. In general,
finding the best possible order is intractable. Therefore we assume that
hierarchical clustering has been applied to the gene expression profiles,
and show that the best order respecting the clustering can be computed
efficiently. We perform experiments comparing the optimal order to several
other methods. The implementation of the algorithm, as well as a simple
program for viewing hierarchically clustered expression array data and
the complete results of our experiments are available at http://monod.uwaterloo.ca/supplements/01expr/
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Comments |
The paper will be submitted to WABI 2001.
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CS-2001-13 |
Title |
Process-Based Representation and Analysis of Framework Instantiation |
Authors |
Paulo S. C. Alencar, Donald D. Cowan, Toacy C. Oliviera,
Carlos J. P. Lucena |
Abstract |
Object-oriented frameworks are currently regarded as a promising
technology for reusing designs and implementations. However, developers
find there is still a steep learning curve when extracting the design rationale
and understanding the framework documentation during framework instantiation.
Thus, instantiation is a costly process in terms of time, people and other
resources. These problems raise a number of questions including: "How
can frameworks be instantiated more quickly and with greater ease? How can
the same high-level design abstractions that were used to develop the framework
be used during framework instantiation instead of using source code as is
done currently? How can we capture the designers' knowledge of the framework
in order to compensate for the loss of key development personnel? How can
we raise the level of abstraction in which the framework evolution and instantiation
is expressed, reasoned about and implemented?" In this paper we present
a process-based approach to framework instantiation that addresses these
issues. Our main goal is to represent the framework architectural design
models in an explicit and declarative way, and support changes to this architecture
based on explicit instantiation processes and activities while maintaining
system integrity, invariants, and general constraints. In this way, the
framework instantiation and evolution can be performed in a valid and controlled
way. To accomplish our goal, we introduce a process-oriented description
of framework instantiation as well as a formal specification of these processes
that allows us to reason about instantiation using model checking techniques.
Discovering instantiation errors and analyzing alternative architectures
and designs early in the development process could certainly lower the cost
and effort in fixing them. Various forms of analysis can be performed using
our approach to check properties such as: structural evolution properties,
pre- and post-conditions of an instantiation, the validity of the processes
associated with extension points, the order of the instantiation processes,
the safety and liveness of these processes, reachability, and deadlocks.
We illustrate our approach with DrawingTool, a framework to provide drawing
features of a case tool.
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CS-2001-12 |
Title |
A Framework For Community Information Systems |
Authors |
Martin Luo, Paulo S. C. Alencar, Donald D. Cowan |
Abstract |
In this paper we present a generic framework architecture
for Web-based community information systems (CIS). The framework has
an open architecture based on COTS (commercial-off-the-shelf) software
components and network technologies. We discuss how a component-based
approach, a layered architecture model, and design patterns can be used
to provide a common framework for CIS. The CIS framework architecture
results in significant benefits that include reuse, a flexible user interface,
powerful search mechanisms and an iintegrated and scalable architecture,
XML and rule-based StyleSheet languages are used for storage, information
search and graphical presentation at the server or client. The overall
framework architecture, its individual components and the interaction
among these components are outlined.
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CS-2001-11 |
Title |
Monotonicity Preserving
and Total Variaion Diminishing Multigrid Time Stepping Methods |
Authors |
A. Jameson and J.W.L.
Wan |
Abstract |
We propose a fast multiplicative and additive multigrid time stepping
schemes for solving linear and nonlinear wave equations in one dimension.
The idea is based on an upwind biased interpolation and residual restriction
operators, and a nonstandard coarse grid update formula for linear equations.
We prove that the two-level schemes preserve monotonicity and are total
variation diminishing, and the same results hold for the multilevel additive
scheme. We generalize the idea to nonlinear equations by solving local
Riemann problems. We demonstrate numerically that these schemes are essentially
nonoscillatory, and that the optimal speed of wave propagation of 2^M-1
is achieved, where M is the number of grids.
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Date |
April 2001 |
Comments |
Conference presentation: Tenth Copper Mountain Conference on Multigrid
Methods
Also appear in virtual proceedings at MGNET.
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CS-2001-10 |
Title |
Using OpenGL for Video
Streaming |
Authors |
P. Gilhuly |
Abstract |
The process of streaming digital video is difficult due to the large
amount of data inherent. Previously, without specialized hardware, video
output has been limited to low resolution or slow playback, as measured
by frames per second.
Many of the functions of a video decoder can be mapped to the capabilities
of a graphics card. However, for the graphics work involved with digital
video a graphics card is required while a video decoder card is not. This
thesis proposes a method to use common graphics cards, through the OpenGL
API, for the task of video streaming.
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Date |
April 2001 |
Comments |
I have included the video sequences I used to test my compressor and
streamer as well as a PostScript and a PDF format of my thesis. Under
the directories Hier and BFI you will find uncompressed AVIs (subsequently
gzipped) of the frames generated by my streamer. Under the directory MPEG
you will find MPEG 1 encoding of the three movies, compressed using default
settings.
MPEG/* - MPEG1 encoded versions of animations
BFI/* - MPOG encoded versions using brute force search
Hier/* - MPOG encoded versions using hierarchical search
thesis.pdf - PDF version of thesis
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MPEG: ball,
geri, tree |
AVI compressed:
geri_br, tree_br,
geri_hi, tree_hi |
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CS-2001-08 |
Title |
Just-in-time subgrammar
extraction for HPSG |
Authors |
V. Keselj |
Abstract |
We define the basic problem of subgrammar extraction for
head-driven phrase structure grammars (HPSG) in the following
way:
Given a large HPSG grammar G and a set of words W,
find a small subgrammar of G that accepts the same
set of sentences from W^* as G, and for each of
them produces the same parse trees.
The set of words W is obtained from a piece of text.
Additionally, we assume that this operation is done
``just-in-time,'' i.e., just before parsing the text. This
application requires that this operation be done in an
automatic and efficient way. After defining the problem in
the general framework, we discuss the problem for context-free
grammars (CFG), and give an efficient algorithm for it.
We show that finding the smallest subgrammar for HPSGs is an
NP-hard problem, and give an efficient algorithm that solves
an easier, approximate version of the problem.
We also discuss how the algorithm can be efficiently
implemented.
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Date |
March 2001 |
Report |
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CS-2001-07 |
Authors |
A. Garcia and D.D. Cowan |
Date |
March 2001 |
Report |
Only available in printed format |
CS-2001-06 |
Title |
Text Structure Recognition
using a Region Algebra |
Authors |
M. Young-Lai |
Abstract |
We consider the problem
of incrementally developing a parser for text structure. This means building
the parser specification a piece at a time while simultaneously developing
our understanding of the text.
We argue that existing solutions have usability and efficiency problems
for this application and propose an alternative approach based on the type
of region algebra that is often used as a query language for text databases.
This is an appropriate interface for incremental development, but has no
efficient batch parsing model such as those that exist for grammars. In
this thesis, we propose an efficient batch parsing model and characterize
the region algebras to which it applies. |
Date |
February 2001 |
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CS-2001-05 |
Title |
Modular HPSG |
Authors |
V. Keselj |
Abstract |
We present a detailed
description of the modular Head-driven Phrase Structure Grammar (HPSG).
Although the notion of modularity is known in the area of programming languages,
and it is described for context-free grammars (CFG), this is the first attempt
of defining modularity for HPSGs.
We describe and formally define modularity for an HPSG-type grammar, and
we illustrate its application on an example.
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Date |
February 2001 |
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CS-2001-04 |
Title |
Optimum Multi-dimensional
Interval Routing Schemes on Networks with Dynamic Cost Links
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Authors |
Y. Ganjali |
Abstract |
One of the fundamental
tasks in any distributed computing system is routing messages between pairs
of nodes. An Interval Routing Scheme (IRS) is a space efficient way of routing
messages in a network. The problem of characterizing graphs that support
an IRS is a well-known problem and has been studied for some variants of
IRS. It is natural to assume that the costs of links may vary over time
(dynamic cost links) and to try to find an IRS which routes all messages
on shortest paths (optimum IRS). In this paper, we study this problem for
a variant of IRS in which the labels assigned to the vertices are d-ary
integer tuples (d-dimensional IRS). The only known results in this case
are for specific graphs like hypercubes, n-dimensional grids, or for the
1-dimensional case. We give a complete characterization for the class of
networks supporting multi-dimensional strict and linear (which is a variation
of IRS) interval routing schemes with dynamic cost links.
Keywords:Interval routing, networks, routing algorithms, dynamic,
multi-dimensional, characterization. |
Date |
March 2001 |
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CS-2001-03 |
Title |
Characterization of Networks
Supporting Multi-dimensional Linear Interval Routing Schemes
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Authors |
Y. Ganjali |
Abstract |
An Interval routing scheme (IRS) is a well-known, space efficient routing
strategy for routing messages in a distributed network. In this scheme,
each node of the network is assigned an integer label and each link at
each node is labeled with an interval. The interval assigned to a link
l at a node v indicates the set of destination addresses which should
be forwarded through l from v. A Multi-dimensional Interval Routing Scheme
(MIRS) is a generalization of IRS in which each node is assigned a multi-dimensional
label (which is a list of d integers for the d-dimensional case). The
labels assigned to the links of the network are also multi-dimensional
(a list of d 1-dimensional intervals). The class of networks supporting
linear IRS (in which the intervals are not cyclic) is already known for
the 1-dimensional case [FG94]. In this paper, we generalize this result
and completely characterize the class of networks supporting linear MIRS
(or MLIRS) for a given number of dimensions d. We show that by increasing
d, the class of networks supporting MLIRS is strictly expanded. We also
give a characterization of the class of networks supporting strict MLIRS,
which is a modified version of MLIRS.
Key words:Computer networks, interval routing schemes, graph theory,
multi-dimensional, characterization.
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Date |
March 2001 |
Comments |
Will be submitted to SIROCCO
2001 |
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CS-2001-02 |
Title |
Reducing the Size of Auxiliary Data Needed to Maintain
Materialized Views by Exploiting Integrity Constraints |
Authors |
L. Stanchev |
Abstract |
A data warehouse consists of materialized views, which contain derived
data from several data sources. The advantage of using materialized views
is that they contain the results of standard queries and therefore when
such queries are posed, the data sources those queries are based on, which
are usually costly to access because of their size and remoteness, don't
have to be accessed. However in order for the materialized views to contain
up-to-data data they have to be updated periodically. Such synchronization
of the materialized views with the data sources could be slow if the later
have to be queries for a correct update to be done - i.e. if just the
data for the changes done to the data sources is insufficient. A way querying
the data sources during materialized view update can be avoided is by
storing any data from the data sources, which could be relevant to an
update of the materialized views, on the data warehouse site. Such auxiliary
data is stored in auxiliary views and has the characteristic that it makes
the data stored at the data warehouse self-maintainable, i.e. it can be
update correctly from the log of changes done to the the data sources.
In this paper we propose unique algorithms for keeping the size of such
auxiliary views relatively small. This is achieved by using the additional
information about the integrity constraints that hold on the data sources.
More specifically we use an object-oriented model to describe a database
schema and a subset of OQL as our query language. The proposed in the
paper algorithms produce auxiliary views that make a materialized view
self-maintainable relative to the three possible operations on a datbase:
addition, deletion and object update.
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Date |
September 2001 |
Comments |
It was submitted to CASCON
2000 as a paper but it was not accepted. The reported was created as a result
of 700 level distributed database course at the University of Waterloo thought
by Prof. Ken Salem. |
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CS-2001-01 |
Title |
Issues in Scalable Distributed-System
Management |
Authors |
P.A.S. Ward |
Abstract |
Distributed-system management
concerns the observation of a distributed computation and then using the
information gained by that observation to control the computation. This
necessitates collecting the information required to determine the partial
order of execution, and then reasoning about that partial order. This in
turn requires a partial-order data structure and, if the reasoning is being
performed by a human, a system for visualizing that partial order. Both
creating such a data structure and visualizing it are hard problems.
Current partial-order data structure techniques suffer various shortcomings.
Potentially scalable mechanisms, such as Ore timestamps, are static. Dynamic
algorithms, on the other hard, either require a significant search operation
to answer basic questions, or they require a vector of size equal to the
width of the partial order for each element stored in the order.
Scalable visualization of a partial order is hard for the same reasons that
drawing any large graph is hard. Any visualization that will be meaningful
to a user requires appropriate abstractions on the data structure, while
preserving the core meaning of the data structure. Such abstraction is difficult.
This report formalizes these problems and identifies the specific difficulties
that must be solved to enable scalable distributed-system management.
Keywords: distributed-system observation, partial-order data structure,
vector timestamp, data-structure visualization, scalability |
Date |
January 2001 |
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