bluuebunny/crossref_metadata_2025 huggingface dataset:
Teaching software development skills early in the Curriculum through software engineering
Authors: Liew C. W.
Published: October 2006

Software engineering is commonly taught as an upper level course in students in computer science. There are many software development skills that can be taught in a software engineering course that are useful in other courses. The development of this course has greatly influenced the types of projects and assignments that are required in the upper level courses. The upper level courses have been able to (1) develop more challenging projects and (2) reduce or eliminate the time spent on teaching development skills.
Fun and games
Authors: Sweedyk Elizabeth , Keller Robert M.
Published: October 2006

Computer and video games have grown to be a major industry but, until recently, have largely been ignored by academia. The last couple of years, however, have seen the emergence of new academic programs, conferences, and journals dedicated to games studies. For the past three years we have used computer games as projects in our introductory software engineering course. Small teams of students build three games across the semester. In this paper we describe the course and discuss its success.
Assessing students' knowledge
Authors: Gharibyan Hasmik
Published: October 2006

The evaluation of students' knowledge is undeniably a very important aspect in the process of education. Two of the most commonly used assessment methods are oral exams and written tests. In the USA in Computer Science Education the preference is generally given to written tests. Although convenient in many ways and effective for many subjects, written tests do not always provide correct evaluation of students' knowledge when it comes to theoretical subjects. In this paper we concentrate on theoretical courses of Computer Science. For these courses we conclude that an oral exam is a better evaluation method; we analyze the challenges instructors face when preparing and grading written tests, we discuss the problems students encounter when taking written tests, and we show the advantages of oral exams over written tests. However, we do not overlook some concerns with oral exams; we talk about these issues and advise the examiner to be aware and considerate of them.
Infusing critical thinking skills into content of AI course
Authors: Krishna Rao M. R. K.
Published: October 2006

This paper describes some of our efforts in infusing critical thinking skills into a course on artificial intelligence. Six thinking skills: parts-whole analysis, compare-and-contrast, decision making, causal explanation, prediction and generalization have been introduced at appropriate places in the course. Using a set of carefully chosen examples, we demonstrate that critical thinking skills can be naturally introduced in the course content of computer curricula at tertiary level. Our analysis shows that infusion of critical thinking skills into course content and their explicit introduction stimulates students thinking and improves their learning ability.
Using simulation and collaboration in CS1 and CS2
Authors: Mendes António José , Gomes Anabela , Esteves Micaela , Marcelino Maria José , Bravo Crescencio , Redondo Miguel Angel
Published: October 2006

In this paper we describe the main approach used in our institutions' basic programming courses. The difficulties we experienced in these courses led us to develop tools that, in our view, help students. We created and use animation-based algorithm tools, program simulation tools and problem solving collaboration support tools. The integration of these tools, plus the addition of some other new approaches, gives us a powerful environment that provides a higher level of support to our students.
Using a windows attack intRusion emulator (AWARE) to teach computer security awareness
Authors: Tobin Donald L. , Ware Michael S.
Published: October 2006

Technology has become a major part of our lives. We are entering an era where almost anyone using a computer must have certain fundamental knowledge on how to protect themselves from attacks while online. In this paper, we describe AWARE, an emulator designed to teach either experienced or casual Windows XP users how to use system-supplied tools to detect potential attacks on their system resources. Our system also has built-in tutorials to help educate the user during their simulated attacks.
eFuzion
Authors: Peiper Chad , Warden David , Chan Ellick , Capitanu Boris , Kamin Sam
Published: October 2006

Established as a research project at the University of Illinois in the spring of 2002, eFuzion has proven to be a valuable and effective pedagogical set of tools. It provides the capacity to both mentor and assess students individually, both during and outside of class. In the summer of 2002, a study we conducted revealed that eFuzion's in-class tools increased student's final grade by more than 6 points. In this paper we describe the evolution of our system and experiences leading up to our "Classroom of the Future" demo for the Grand Opening of the Thomas M. Siebel Center for Computer Science. We conclude with a discussion of our future plans for eFuzion.
Classes as first class objects in an environment-passing interpreter
Authors: Fossum T. V.
Published: October 2006

We describe an expression-based programming language that treats classes as first-class objects. We show an implementation of this language using an environment-passing interpreter accessible to students in a programming language class. We also show how to extend this language with properties (as in the C# programming language).
Team formation methods for increasing interaction during in-class group work
Authors: Deibel Katherine
Published: October 2006

In contrast to the student teams used for larger and longer group projects, in-class groups are often ephemeral, lasting for only a few minutes or until the end of the period. Because of this, little effort is put into forming these groups, usually letting the students self-select their teams. This paper argues that greater student interaction and learning can take place by usinginstructor-selected teams. Two group formation techniques for in-class group work, the latent jigsaw method and grouping students by Felder-Silverman learning styles, are presented. Observations from a classroom deployment of these techniques are also described.
Investigating pair-programming in a 2
nd
-year software development and design computer science course
Authors: Mendes Emilia , Al-Fakhri Lubna Basil , Luxton-Reilly Andrew
Published: October 2006

This paper presents the results of a pair programming experiment conducted at the University of Auckland (NZ) during the first semester of 2004. It involved 300 second year Computer Science students attending a software design and construction course. We investigated similar issues to those reported in [26] and employed a subset of the questionnaires used by Laurie Williams et al. on the experiments presented in [26]. Our results support the use of pair programming as an effective programming/design learning technique.
NetPrIDE an integrated environment for developing and visualizing computer network protocols
Authors: Crescenzi Pilu , Gambosi Giorgio , Innocenti Gaia
Published: October 2006

In this paper we present NetPrIDE, an integrated development environment for designing, implementing and visualizing computer network protocols, which has primarily been used for teaching computer networks. NetPrIDE makes use of an abstract and formal notation to clearly and firmly specify a protocol: once the protocol has been specified and the network topology has been fixed, the implementation and the visualization of the protocol is performed in a completely automated way.
Interactive manipulation of regular objects with FAdo
Authors: Moreira Nelma , Reis Rogério
Published: October 2006

FAdo
1
is an ongoing project which aims the development of an interactive environment for symbolic manipulation of formal languages. In this paper we focus in the description of interactive tools for teaching and assisting research on regular languages, and in particular finite automata and regular expressions. Those tools implement most standard automata operations, conversion between automata and regular expressions, and word recognition. We illustrate their use in training and automatic assessment. Finally we present a graphical environment for editing and interactive visualisation.
Virtual student teams
Authors: Goold Annegret , Pears Arnold , Last Mary Z. , Beaumont Chris , Chew Swee Cheng
Published: October 2006

In this panel presentation, the five members will discuss their experiences of working with students in virtual teams. They will share some of the issues and problems they have had and also highlight some of the opportunities and challenges for students working collaboratively together.The virtual student team is defined as a group of students who have come together to perform a certain task and who communicate electronically to achieve that task. Student groups are transformed into teams with structure, purpose and the potential to achieve effective project work. The teams are temporary in that they may exist for a semester or for the life of a particular assessment task or project. Virtual student teams are usually geographically dispersed and thus often have members who are culturally different. There is a heavy reliance on the use of ICT for communication and collaboration within the team.The members of the panel have all had some research experience with teams and teamwork. They have all had different experiences with setting up and managing virtual student teams.
Reverse engineering technique to enhance software engineering education
Authors: Ghafarian Ahmad K.
Published: October 2006

This poster presents our experience incorporating reverse engineering techniques on software engineering education to enhance the productivity of students' team projects. In this approach, the students were provided with an existing working software by the instructor. They were asked to evaluate the software, use the knowledge from the software's behavior and the application domain to define the task scenarios that reflect the interaction pattern and the services that the system provides to its environment. Consequently, the extracted patterns were used to develop the architectural design of the software system and rebuild a modified version of the software.
Application of topic maps in e-learning environment
Authors: Olsevicova Kamila
Published: October 2006

The objective of the poster is to describe the application of topic maps technology in context of e-learning environment used at the university. Topic maps documents are presented as tool that can simplify navigation in plenty of various information and knowledge resources: except common digital learning objects, also printed materials or contacts to human experts can be linked to a single topic map document.
Extending undergraduate CS programs with informatics
Authors: Kay David G. , van der Hoek André , Richardson Debra J.
Published: October 2006

In this poster we describe the diversification of our undergraduate curricula in the computing disciplines at UC Irvine, in particular the creation of Bachelor of Science degree in Informatics.
ExploreCSEd
Authors: Stamouli Ioanna , Begum Marjahan , Mancy Rebecca
Published: October 2006

ExploreCSEd is a collaborative project funded by the HE Academy - Information and Computer Sciences. The aim of the project is to investigate the skills and difficulties involved in learning to program by gathering data from students and educators in multiple institutions and bringing these together for analysis.
Knowledge-based support of newcomers integration into an organization
Authors: Bures Vladimir , Ponce Daniela
Published: October 2006

Every employer should try to help new employees to integrate and adapt into an organization. The realization of organizational processes can be facilitated once the necessary information can be easily retrieved and the proper task-solving procedure is learnt. To support the tasks solution several tools have been designed: e-course, "Yellow Pages" and Communities of Practice and Interest.
Development of object-understanding among students in the humanities
Authors: Lindholm Morten
Published: October 2006

This paper describes a on-going empirical study, inspired by phenomenography, aiming at understanding how students from the humanities learn the concepts of objects and object-orientation during a programming course.
Academic jeopardy
Authors: Bergin Joseph
Published: October 2006

A simple Java application is presented that can assist an instructor to carry on a review of a linked set of topics in a fun way. It encourages students to express the necessary ideas in their own words. It is available from the author.
MIG21 API
Authors: Morgado Carmen , Soares Luís
Published: October 2006

In this poster we present the MIG21 API's main functionalities and two example applications.
A platform for the generation of virtual environments inhabited by intelligent virtual humans
Authors: Silvestre Miguel , Pinto-Albuquerque Maria , Carmo M. B. , Cláudio A. P. , Cunha J. D. , Coelho H.
Published: October 2006

We describe a platform to build virtual environments inhabited by autonomous virtual humans. We propose an architecture comprising several software components assembled to define a platform. The architecture includes a 3D-modelling software, a rendering engine, a library for simulating rigid body dynamics and an agent development framework.
Traditional and more "exotic" .NET languages
Authors: Geller Viktor , Scharff Christelle
Published: October 2006

We study the .NET platform, various .NET languages and their interoperability (with an emphasis on C# and SML .NET), compare C# and Java 1.5, and develop related educational material to be used in a Programming Paradigms course. Introducing .NET - one platform supporting different paradigms - in such a course seems to be a unique experience in Computer Science Education. It may be a motivating factor for students to learn new programming languages.
Evolution lab
Authors: Larkworthy Thomas
Published: October 2006

Evolution Lab is a software engineering MEng. project that allows complex robot designs to be simulated in a real world environment. Evolution Lab was created as a research tool. The system is extendible and embeddable so that it can be customized for use in a wide area of robotic problem domains. It has also been engineered to be user friendly so that its standard features are quickly available to the user without the need of extensive documentation. Included with Evolution Lab is an evolutionary computing library, this allows the system to be used in the evolutionary robotics domain.
Reusable learning objects
Authors: Vinha Antonio
Published: October 2006

This poster describes a project that consists of a study about the reusability of Learning Objects (LOs), focused in educational aspects, and based on an empirical investigation. This investigation uses the evaluation approach and is currently in progress.The poster briefly explains the nature of LOs, the reusability concept and the methodology used in the project.
Variant parametric types
Authors: Igarashi Atsushi , Viroli Mirko
Published: October 2006

We develop the mechanism of
variant parametric types
as a means to enhance synergy between parametric and inclusion polymorphism in object-oriented programming languages. Variant parametric types are used to control both the subtyping between different instantiations of one generic class and the accessibility of their fields and methods. On one hand, one parametric class can be used to derive covariant types, contravariant types, and bivariant types (generally called variant parametric types) by attaching a variance annotation to a type argument. On the other hand, the type system prohibits certain method/field accesses, according to variance annotations, when these accesses may otherwise make the program unsafe. By exploiting variant parametric types, a programmer can write generic code abstractions that work on a wide range of parametric types in a safe manner. For instance, a method that only reads the elements of a container of numbers can be easily modified so as to accept containers of integers, floating-point numbers, or any subtype of the number type.Technical subtleties in typing for the proposed mechanism are addressed in terms of an intuitive correspondence between variant parametric and bounded existential types. Then, for a rigorous argument of correctness of the proposed typing rules, we extend Featherweight GJ---an existing formal core calculus for Java with generics---with variant parametric types and prove type soundness.
An approximation algorithm for scheduling malleable tasks under general precedence constraints
Authors: Jansen Klaus , Zhang Hu
Published: October 2006

In this article, we study the problem of scheduling malleable tasks with precedence constraints. We are given
m
identical processors and
n
tasks. For each task the processing time is a function of the number of processors allotted to it. In addition, the tasks must be processed according to the precedence constraints. The goal is to minimize the makespan (maximum completion time) of the resulting schedule. The best previous approximation algorithm (that works in two phases) in Lepère et al. [2002b] has a ratio 3 + √5≈ 5.236. We develop an improved approximation algorithm with a ratio at most 100/43 + 100(√4349 − 7)/2451 ≈ 4.730598. We also show that our resulting ratio is asymptotically tight.
Synthesizing safe state machines from Esterel
Authors: Prochnow Steffen , Traulsen Claus , von Hanxleden Reinhard
Published: October 2006

Esterel and Safe State Machines (SSMs) are synchronous languages dedicated to the modeling of embedded reactive systems. While Esterel is a textual language, SSMs are based on the graphical Statecharts formalism. Statecharts are often more intuitive to understand than their textual counterpart, and their animated simulation can help to visualize subtle behaviors of a program. However, in terms of editing speed, revision management, and meta-modeling, the textual nature of Esterel is advantageous. We present an approach to transform Esterel v5 programs into equivalent SSMs. This permits a design flow where the designer develops a system at the Esterel level, but uses a graphical browser and simulator to inspect and validate the system under development.We synthesize SSMs in two phases. The first phase transforms an Esterel program into an equivalent SSM, using a structural translation that results in correct, but typically not very compact SSMs. The second phase iteratively applies optimization rules that aim to reduce the number of states, transitions and hierarchy levels to enhance readability of the SSM. As it turned out, this optimization is also useful for the traditional, manual design of SSMs. The complete transformation has been implemented in a prototypical modeling environment, which allows to demonstrate the practicality of this approach and the compactness of the generated SSMs.
Area and delay estimation for FPGA implementation of coarse-grained reconfigurable architectures
Authors: Yan Leipo , Srikanthan Thambipillai , Gang Niu
Published: October 2006

Reconfigurable architecture is one solution to the increasing computational requirement that often cannot be met by the low-end embedded processors. Compiling applications to such architectures involves hardware/software partitioning. To partition the applications, a set of parameters, such as the hardware execution time and hardware area consumption, is required for each application block. Quick derivation of the parameters for all the blocks is essential. Previous research has shown that the coarse-grained reconfigurable architectures are able to accelerate the applications. However, no research effort has been made to find the area and time for application blocks implemented on such architectures. In this paper we present an estimation model for the coarse-grained reconfigurable architectures implemented on FPGA platforms. The estimation model is able to quickly produce an area-time graph, which shows the area and time relationship, for each application block. The accuracy of the estimation model has been verified on real applications. Experiment shows that the estimation error for the area consumption is within 13% and the estimation error for the time is within 8%.
Programming monads operationally with Unimo
Authors: Lin Chuan-kai
Published: October 2006

Monads are widely used in Haskell for modeling computational effects, but defining monads remains a daunting challenge. Since every part of a monad's definition depends on its computational effects, programmers cannot leverage the common behavior of all monads easily and thus must build from scratch each monad that models a new computational effect.I propose the Unimo framework which allows programmers to define monads and monad transformers in a modular manner. Unimo contains a heavily parameterized observer function which enforces the monad laws, and programmers define a monad by invoking the observer function with arguments that specify the computational effects of the monad. Since Unimo provides the common behavior of all monads in a reusable form, programmers no longer need to rebuild the semantic boilerplate for each monad and can instead focus on the more interesting and rewarding task of modeling the desired computational effects.
The pendulum swings back
Authors: Fang Yulin , Neufeld Derrick J.
Published: October 2006

After two decades of actively distributing computing power to individual users in the form of desktop and notebook PCs, IT executives are now being drawn back to the benefits of centralized computing platforms, as evidenced by the emergence of thin client technology and the application service provider (ASP) business model. But will individual users embrace this "re-centralization?" This study examines major influencing factors on end-user use of centralized application platforms using the theory of planned behavior (TPB). Two new perceived behavioral control factors are identified: (1) relative functional advantage of the local PC versus the central server, and (2) response promptness of the central server. Data were collected using a paper-and-pencil survey of twenty-six users who had access to a centralized application platform. The two new measures demonstrated satisfactory reliability and validity, and both were strong predictors of intention to use the centralized platform and actual usage. Results also suggest that TPB has strong predictive power for individual use of centralized application platforms.
Human versus automated facilitation in the GSS context
Authors: Limayem Moez
Published: October 2006

Many group support systems (GSS) are currently being used with the help of a human facilitator who guides the group members through their use of the decision models. Another way to guide the use of these systems is to embed some facilitation mechanisms into the GSS itself (i.e., automated facilitation). Using the Adaptive Structuration Theory, this study investigated the tradeoffs associated with human facilitation and automated facilitation. Groups using a multicriteria decision model in the context of a resource allocation task were exposed to one of two experimental conditions: (1) human facilitation, or (2) automated facilitation. Results indicated that automated facilitation, embedded in the GSS, was as effective as human facilitation in enhancing the faithfulness of appropriation of the technology.
Locally testable codes and PCPs of almost-linear length
Authors: Goldreich Oded , Sudan Madhu
Published: October 2006

We initiate a systematic study of locally testable codes; that is, error-correcting codes that admit very efficient membership tests. Specifically, these are codes accompanied with tests that make a constant number of (random) queries into any given word and reject non-codewords with probability proportional to their distance from the code.Locally testable codes are believed to be the combinatorial core of PCPs. However, the relation is less immediate than commonly believed. Nevertheless, we show that certain PCP systems can be modified to yield locally testable codes. On the other hand, we adapt techniques that we develop for the construction of the latter to yield new PCPs.Our main results are locally testable codes and PCPs of almost-linear length. Specifically, we prove the existence of the following constructs:---Locally testable binary (linear) codes in which
k
information bits are encoded by a codeword of length
k
⋅ exp(Õ(√(log
k
))). This improves over previous results that either yield codewords of exponential length or obtained almost quadratic length codewords for sufficiently large nonbinary alphabet.---PCP systems of almost-linear length for SAT. The length of the proof is
n
⋅ exp(Õ(√(log
n
))) and verification in performed by a constant number (i.e., 19) of queries, as opposed to previous results that used proof length
n

(1 +
O
(1/
q
))

for verification by
q
queries.The novel techniques in use include a random projection of certain codewords and PCP-oracles that preserves local-testability, an adaptation of PCP constructions to obtain “linear PCP-oracles” for proving conjunctions of linear conditions, and design of PCPs with some new soundness properties---a direct construction of locally testable (linear) codes of subexponential length.
Distribution sort with randomized cycling
Authors: Vitter Jeffrey Scott , Hutchinson David Alexander
Published: October 2006

Parallel independent disks can enhance the performance of external memory (EM) algorithms, but the programming task is often difficult. Each disk can service only one read or write request at a time; the challenge is to keep the disks as busy as possible. In this article, we develop a randomized allocation discipline for parallel independent disks, called
randomized cycling
. We show how it can be used as the basis for an efficient distribution sort algorithm, which we call
randomized cycling distribution sort
(RCD). We prove that the expected I/O complexity of RCD is optimal. The analysis uses a novel reduction to a scenario with significantly fewer probabilistic interdependencies. We demonstrate RCD's practicality by experimental simulations. Using the randomized cycling discipline, algorithms developed for the unrealistic multihead disk model can be simulated on the realistic parallel disk model for the class of
multipass
algorithms, which make a complete pass through their data before accessing any element a second time. In particular, algorithms based upon the well-known distribution and merge paradigms of EM computation can be optimally extended from a single disk to parallel disks.
Managing bounded code caches in dynamic binary optimization systems
Authors: Hazelwood Kim , Smith Michael D.
Published: October 2006

Dynamic binary optimizers store altered copies of original program instructions in software-managed code caches in order to maximize reuse of transformed code. Code caches store code blocks that may vary in size, reference other code blocks, and carry a high replacement overhead. These unique constraints reduce the effectiveness of conventional cache management policies. Our work directly addresses these unique constraints and presents several contributions to the code-cache management problem. First, we show that evicting more than the minimum number of code blocks from the code cache results in less run-time overhead than the existing alternatives. Such
granular
evictions reduce overall execution time, as the fixed costs of invoking the eviction mechanism are amortized across multiple cache insertions. Second, a study of the ideal lifetimes of dynamically generated code blocks illustrates the benefit of a replacement algorithm based on a generational heuristic. We describe and evaluate a generational approach to code cache management that makes it easy to identify long-lived code blocks and simultaneously avoid any fragmentation because of the eviction of short-lived blocks. Finally, we present results from an implementation of our generational approach in the DynamoRIO framework and illustrate that, as dynamic optimization systems become more prevalent, effective code cache-management policies will be essential for reliable, scalable performance of modern applications.
First workshop on sharing and reusing architectural knowledge
Authors: Lago Patricia , Avgeriou Paris
Published: October 2006

The first SHARK (SHAring and Reusing architectural Knowledge) workshop, attempted to explore the state of the art as well as the state of the practice in this emerging field. This workshop report presents the themes of the workshop, it summarizes the results of the discussions held about various topics, and suggests some research topics that are worthwhile to pursue in the future.
Only 365 days left until the Sigcomm deadline
Authors: Crowcroft Jon , Kreibich Christian
Published: October 2006

Only three hundred sixty four days left until the Sigcomm deadline. Only three hundred sixty three days left until the Sigcomm deadline. Only three hundred sixty two days left until the Sigcomm deadline. Only three hundred sixty one days left until the Sigcomm deadline. Only three hundred sixty days left until the Sigcomm deadline. Only three hundred fifty nine days left until the Sigcomm deadline. Only three hundred fifty eight days left until the Sigcomm deadline. Only three hundred fifty seven days left until the Sigcomm deadline. Only three hundred fifty six days left until the Sigcomm deadline. Only three hundred fifty five days left until the Sigcomm deadline.
An out-of-core sparse symmetric-indefinite factorization method
Authors: Meshar Omer , Irony Dror , Toledo Sivan
Published: October 2006

We present a new out-of-core sparse symmetric-indefinite factorization algorithm. The most significant innovation of the new algorithm is a dynamic partitioning method for the sparse factor. This partitioning method results in very low I/O traffic and allows the algorithm to run at high computational rates, even though the factor is stored on a slow disk. Our implementation of the new code compares well with both high-performance in-core sparse symmetric-indefinite codes and a high-performance out-of-core sparse Cholesky code.
Studying the current status of technology adoption
Authors: Bharati Pratyush , Chaudhury Abhijit
Published: October 2006

Examining the extent and nature of adoption of technologies by micro, small, and medium-sized manufacturing firms in the greater Boston area.
Can distributed software development be agile?
Authors: Ramesh Balasubramaniam , Cao Lan , Mohan Kannan , Xu Peng
Published: October 2006

Three organizations studied here suggest the answer is "yes," when the unique characteristics of both environments are successfully blended.
Transforming policies into mechanisms with infokernel
Authors: Arpaci-Dusseau Andrea C. , Arpaci-Dusseau Remzi H. , Burnett Nathan C. , Denehy Timothy E. , Engle Thomas J. , Gunawi Haryadi S. , Nugent James A. , Popovici Florentina I.
Published: October 2006

We describe an evolutionary path that allows operating systems to be used in a more flexible and appropriate manner by higher-level services. An infokernel exposes key pieces of information about its algorithms and internal state; thus, its default policies become mechanisms, which can be controlled from user-level. We have implemented two prototype infokernels based on the linuxtwofour and netbsdver kernels, called infolinux and infobsd, respectively. The infokernels export key abstractions as well as basic information primitives. Using infolinux, we have implemented four case studies showing that policies within Linux can be manipulated outside of the kernel. Specifically, we show that the default file cache replacement algorithm, file layout policy, disk scheduling algorithm, and TCP congestion control algorithm can each be turned into base mechanisms. For each case study, we have found that infokernel abstractions can be implemented with little code and that the overhead and accuracy of synthesizing policies at user-level is acceptable.
Xen and the art of virtualization
Authors: Barham Paul , Dragovic Boris , Fraser Keir , Hand Steven , Harris Tim , Ho Alex , Neugebauer Rolf , Pratt Ian , Warfield Andrew
Published: October 2006

Numerous systems have been designed which use virtualization to subdivide the ample resources of a modern computer. Some require specialized hardware, or cannot support commodity operating systems. Some target 100% binary compatibility at the expense of performance. Others sacrifice security or functionality for speed. Few offer resource isolation or performance guarantees; most provide only best-effort provisioning, risking denial of service.This paper presents Xen, an x86 virtual machine monitor which allows multiple commodity operating systems to share conventional hardware in a safe and resource managed fashion, but without sacrificing either performance or functionality. This is achieved by providing an idealized virtual machine abstraction to which operating systems such as Linux, BSD and Windows XP, can be
ported
with minimal effort.Our design is targeted at hosting up to 100 virtual machine instances simultaneously on a modern server. The virtualization approach taken by Xen is extremely efficient: we allow operating systems such as Linux and Windows XP to be hosted simultaneously for a negligible performance overhead --- at most a few percent compared with the unvirtualized case. We considerably outperform competing commercial and freely available solutions in a range of microbenchmarks and system-wide tests.
Aggregability is NP-hard
Authors: Kreinovich Vladik , Shpak Max
Published: October 2006

Many dynamical systems are
aggregable
in the sense that we can divide their variables
x
1
,...,
x

n

into several (
k
) non-intersecting groups and find combinations
y
1
,...,

y
k

of variables from these groups (
macrovariables
) whose dynamics depend only on the initial values of the macrovariables. For very large systems, finding such an aggregation is often the only way to perform a meaningful analysis of such systems. Since aggregation is important, researchers have been trying to find a general efficient algorithm for detecting aggregability. In this paper, we show that in general, detecting aggregability is NP-hard even for linear systems, and thus (unless P=NP), we can only hope to find efficient detection algorithms for specific classes of systems.We also show that in the linear case, once the groups are known, it is possible to efficiently find appropriate combinations
ya
.
Computational geometry column 48
Authors: O'Rourke Joseph
Published: October 2006

A new class of art gallery-like problems inspired by wireless localization is discussed.
Higher-order abstract syntax
Authors: Crary Karl , Harper Robert
Published: October 2006

A recent SIGACT News Logic column, guest-written by James Cheney
DOI =
10.1145/1107523.1107537
, discussed nominal logic [1], an
approach to abstract syntax with binding structure. In addition to
providing a worthy tutorial on nominal logic, that column leveled
five criticisms at higher-order abstract syntax, an alternative
approach for dealing with binding structure in abstract syntax. We
argue below that three of those criticisms are factually
inaccurate, and the other two are misguided.
Spatial graph grammars for graphical user interfaces
Authors: Kong Jun , Zhang Kang , Zeng Xiaoqin
Published: October 2006

In a graphical user interface, physical layout and abstract structure are two important aspects of a graph. This article proposes a new graph grammar formalism which integrates both the spatial and structural specification mechanisms in a single framework. This formalism is equipped with a parser that performs in polynomial time with an improved parsing complexity over its nonspatial predecessor, that is, the Reserved Graph Grammar. With the extended expressive power, the formalism is suitable for many user interface applications. The article presents its application in adaptive Web design and presentation.
Probabilistic information retrieval approach for ranking of database query results
Authors: Chaudhuri Surajit , Das Gautam , Hristidis Vagelis , Weikum Gerhard
Published: October 2006

We investigate the problem of ranking the answers to a database query when many tuples are returned. In particular, we present methodologies to tackle the problem for conjunctive and range queries, by adapting and applying principles of probabilistic models from information retrieval for structured data. Our solution is domain independent and leverages data and workload statistics and correlations. We evaluate the quality of our approach with a user survey on a real database. Furthermore, we present and experimentally evaluate algorithms to efficiently retrieve the top ranked results, which demonstrate the feasibility of our ranking system.
Evaluation of a multiscale color model for visual difference prediction
Authors: Lovell P. George , Párraga C. Alejandro , Troscianko Tom , Ripamonti Caterina , Tolhurst David J.
Published: October 2006

How different are two images when viewed by a human observer? There is a class of computational models which attempt to predict perceived differences between subtly different images. These are derived from theoretical considerations of human vision and are mostly validated from psychophysical experiments on stimuli, such as sinusoidal gratings. We are developing a model of visual difference prediction, based on multiscale analysis of local contrast, to be tested with psychophysical discrimination experiments on natural-scene stimuli. Here, we extend our model to account for differences in the chromatic domain by modeling differences in the luminance domain and in two opponent chromatic domains. We describe psychophysical measurements of objective (discrimination thresholds) and subjective (magnitude estimations) perceptual differences between visual stimuli derived from colored photographs of natural scenes. We use one set of psychophysical data to determine the best parameters for the model and then determine the extent to which the model generalizes to other experimental data. In particular, we show that the cues from different spatial scales and from the separate luminance and chromatic channels contribute roughly equally to discrimination and that these several cues are combined in a relatively straightforward manner. In general, the model provides good predictions of both threshold and suprathreshold image differences arising from a wide variety of geometrical and optical manipulations. This implies that models of this class can be generally useful in specifying how different two similar images will look to human observers.
Cognitive factors can influence self-motion perception (vection) in virtual reality
Authors: Riecke Bernhard E. , Schulte-Pelkum Jörg , Avraamides Marios N. , Heyde Markus Von Der , Bülthoff Heinrich H.
Published: October 2006

Research on self-motion perception and simulation has traditionally focused on the contribution of physical stimulus properties (“bottom-up factors”) using abstract stimuli. Here, we demonstrate that cognitive (“top-down”) mechanisms like ecological relevance and presence evoked by a virtual environment can also enhance visually induced self-motion illusions (vection). In two experiments, naive observers were asked to rate presence and the onset, intensity, and convincingness of circular vection induced by different rotating visual stimuli presented on a curved projection screen (FOV: 54° × 45°). Globally consistent stimuli depicting a natural 3D scene proved more effective in inducing vection and presence than inconsistent (scrambled) or unnatural (upside-down) stimuli with similar physical stimulus properties. Correlation analyses suggest a direct relationship between spatial presence and vection. We propose that the coherent pictorial depth cues and the spatial reference frame evoked by the naturalistic environment increased the believability of the visual stimulus, such that it was more easily accepted as a stable “scene” with respect to which visual motion is more likely to be judged as self-motion than object motion. This work extends our understanding of mechanisms underlying self-motion perception and might thus help to improve the effectiveness and believability of virtual reality applications.
c-Jun NH2-Terminal Kinase 2α2 Promotes the Tumorigenicity of Human Glioblastoma Cells
Authors: Cui Jian , Han Shuang-Yin , Wang Congli , Su Wanwen , Harshyne Larry , Holgado-Madruga Marina , Wong Albert J.
Published: October 2006

c-Jun NH2-terminal kinases (JNK) are members of the mitogen-activated protein kinase family and have been implicated in the formation of several human tumors, especially gliomas. We have previously shown that a 55 kDa JNK isoform is constitutively active in 86% of human brain tumors and then showed that it is specifically a JNK2 isoform and likely to be either JNK2α2 or JNK2β2. Notably, we found that only JNK2 isoforms possess intrinsic autophosphorylation activity and that JNK2α2 has the strongest activity. In the present study, we have further explored the contribution of JNK2 isoforms to brain tumor formation. Analysis of mRNA expression by reverse transcription-PCR revealed that JNK2α2 is expressed in 91% (10 of 11) of glioblastoma tumors, whereas JNK2β2 is found in only 27% (3 of 11) of tumors. Both JNK2α2 and JNK2β2 mRNAs are expressed in normal brain (3 of 3). Using an antibody specific for JNK2α isoforms, we verified that JNK2α2 protein is expressed in 88.2% (15 of 17) of glioblastomas, but, interestingly, no JNK2α2 protein was found in six normal brain samples. To evaluate biological function, we transfected U87MG cells with green fluorescent protein–tagged versions of JNK1α1, JNK2α2, and JNK2α2APF (a dominant-negative mutant), and derived cell lines with stable expression. Each cell line was evaluated for various tumorigenic variables including cellular growth, soft agar colony formation, and tumor formation in athymic nude mice. In each assay, JNK2α2 was found to be the most effective in promoting that phenotype. To identify effectors specifically affected by JNK2α2, we analyzed gene expression. Gene profiling showed several genes whose expression was specifically up-regulated by JNK2α2 but down-regulated by JNK2α2APF, among which eukaryotic translation initiation factor 4E (eIF4E) shows the greatest change. Because AKT acts on eIF4E, we also examined AKT activation. Unexpectedly, we found that JNK2α2 could specifically activate AKT. Our data provides evidence that JNK2α2 is the major active JNK isoform and is involved in the promotion of proliferation and growth of human glioblastoma tumors through specific activation of AKT and overexpression of eIF4E. (Cancer Res 2006; 66(20): 10024-31)
Probing the Intracellular Redox Status of Tumors with Magnetic Resonance Imaging and Redox-Sensitive Contrast Agents
Authors: Hyodo Fuminori , Matsumoto Ken-ichiro , Matsumoto Atsuko , Mitchell James B. , Krishna Murali C.
Published: October 2006

Nitroxide radicals are paramagnetic contrast agents, used in magnetic resonance imaging (MRI), that also exert antioxidant effects. Participating in cellular redox reactions, they lose their ability to provide contrast as a function of time after administration. In this study, the rate of contrast loss was correlated to the reducing power of the tissue or the “redox status.” The preferential reduction of nitroxides in tumors compared with normal tissue was observed by MRI. The influence of the structure of the nitroxide on the reduction rate was investigated by MRI using two cell-permeable nitroxides, 4-hydroxy-2,2,6,6,-tetramethyl-1-piperidynyloxyl (Tempol) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (3CP), and one cell-impermeable nitroxide, 3-carboxy-2,2,5,5,5-tetramethylpyrrolidine-1-oxyl (3CxP). Pharmacokinetic images of these nitroxides in normal tissue, tumor, kidney, and artery regions in mice were simultaneously obtained using MRI. The decay of Tempol and 3CP in tumor tissue was significantly faster than in normal tissue. No significant change in the total nitroxide (oxidized + reduced forms) was noted from tissue extracts, suggesting that the loss in contrast as a function of time is a result of intracellular bioreduction. However, in the case of 3CxP (membrane impermeable), there was no difference in the reduction rates between normal and tumor tissue. The time course of T1 enhancement by 3CxP and the total amount of 3CxP (oxidized + reduced) in the femoral region showed similar pharmacokinetics. These results show that the differential bioreduction of cell-permeable nitroxides in tumor and normal tissue is supported by intracellular processes and the reduction rates are a means by which the intracellular redox status can be assessed noninvasively. (Cancer Res 2006; 66(20): 9921-8)
Characterizing Vascular Parameters in Hypoxic Regions: A Combined Magnetic Resonance and Optical Imaging Study of a Human Prostate Cancer Model
Authors: Raman Venu , Artemov Dmitri , Pathak Arvind P. , Winnard Paul T. , McNutt Stephen , Yudina Anna , Bogdanov Alexei , Bhujwalla Zaver M.
Published: October 2006

The integration of imaging technologies with the capabilities of genetic engineering has created novel opportunities for understanding and imaging cancer. Here, we have combined vascular magnetic resonance imaging (MRI) and optical imaging to understand the relationship between hypoxia and vascularization in a human prostate cancer model engineered to express enhanced green fluorescent protein (EGFP) under hypoxia. Characterization and validation of EGFP expression under hypoxic conditions was done in culture and in solid tumors in vivo. MRI measurements showed that vascular volume was significantly lower in fluorescing regions. These regions also frequently exhibited high permeability. These data were further supported by the detection of low vessel density in EGFP-positive regions, as determined by the distribution of intravascularly administered, fluorescence-labeled Lycopersicon esculentum lectin in frozen tumor sections. These observations are consistent with the possibility that regions of low vascular volumes are hypoxic, which induces increased expression of functionally active vascular endothelial growth factor, a potent vascular permeability factor. (Cancer Res 2006; 12(20): 9929-36)
Signal Transducers and Activators of Transcription 5b Activation Enhances Hepatocellular Carcinoma Aggressiveness through Induction of Epithelial-Mesenchymal Transition
Authors: Lee Terence K. , Man Kwan , Poon Ronnie T.P. , Lo Chung Mau , Yuen Anthony P. , Ng Irene O. , Ng Kevin T. , Leonard Warren , Fan Sheung Tat
Published: October 2006

Poor prognosis of hepatocellular carcinoma (HCC) is associated with a high potential of vascular invasion and metastasis. Epithelial-mesenchymal transition (EMT) is a key event in the tumor invasion process. Recently, signal transducers and activators of transcription 5 (STAT5) has been linked to tumor progression by EMT induction. However, the precise roles of STAT5 genes (STAT5a and STAT5b) in human epithelial cancers have not been elucidated clearly. The aim of this study is to analyze the roles of STAT5 isoforms in HCC progression using HCC clinical samples. We showed that activation of STAT5b, but not STAT5a, was found in HCC clinical samples and its expression was significantly associated with younger age (P = 0.037), advanced tumor stages (P = 0.003), venous infiltration (P = 0.016), microsatellite formation (P = 0.024), multiple tumor nodules (P = 0.02), and poor patient survival. To specifically investigate the mechanism underlying constitutive activation of STAT5b in HCC, EGFP-HBX was introduced into Huh-7 cells. STAT5b activation in HCC is at least partially mediated by HBX activation. Ectopic STAT5b transfection conferred increased HCC cell motility and invasiveness by induction of EMT changes. In conclusion, STAT5b activation enhanced HCC aggressiveness by induction of EMT, which was possibly mediated by HBX activation. STAT5b could serve as a novel molecular target for HCC treatment. (Cancer Res 2006; 66(20): 9948-56)