bluuebunny/crossref_metadata_2025 huggingface dataset:
A NEW FRAMEWORK FOR DYNAMIC CREDIT PORTFOLIO LOSS MODELLING
Authors: SIDENIUS JAKOB , PITERBARG VLADIMIR , ANDERSEN LEIF
Published: April 2008

We present the SPA framework, a novel approach to the modeling of the dynamics of portfolio default losses. In this framework, models are specified by a two-layer process. The first layer models the dynamics of portfolio loss distributions in the absence of information about default times. This background process can be explicitly calibrated to the full grid of marginal loss distributions as implied by initial CDO tranche values indexed on maturity, as well as to the prices of suitable options. We give sufficient conditions for consistent dynamics. The second layer models the loss process itself as a Markov process conditioned on the path taken by the background process. The choice of loss process is non-unique. We present a number of choices, and discuss their advantages and disadvantages. Several concrete model examples are given, and valuation in the new framework is described in detail. Among the specific securities for which algorithms are presented are CDO tranche options and leveraged super-senior tranches.
A CUSTOMER-ORIENTED DECISION AGENT FOR PRODUCT SELECTION IN WEB-BASED SERVICES
Authors: AL-AOMAR RAID , DWEIRI FIKRI
Published: April 2008

This paper describes a web-based Decision Agent (DA) that provides a customer-oriented approach for selecting products in online orders. The proposed approach is focused on enhancing the front-end of company's business portal by segmenting prospective online customers and directing them to use decision modules that improve user perception in terms of effort, accuracy, and acceptance. The user's Consistency Ratio (CR) in evaluating the attributes of online products is used to categorize prospected users and to direct them to proceed with one of three decision modules, Analytical Hierarchy Process (AHP), Simple Multi-Attribute Rating Technique (SMART), and Direct Scaling Method (DSM). The proposed approach is applied to an online cellular phone selection case study. Experimental results showed the fit of assigned decision modules to customer classes where users made smart phone selections with less effort and higher reported convenience and satisfaction. The approach can be tailored for other online products and can be integrated into the websites of producers and online stores in a wide range of business applications.
IMPROVED PROJECTION HOPFIELD NETWORK FOR THE QUADRATIC ASSIGNMENT PROBLEM
Authors: TATSUMI KEIJI , TANINO TETSUZO
Published: April 2008

The continuous-valued Hopfield neural network (CHN) is a popular and powerful metaheuristic method for combinatorial optimization. However, it is difficult to select appropriate penalty parameters for constraints so as to obtain a feasible and desirable solution by CHN. Thus, various improved models have been proposed. Matsuda proposed a CHN named optimal CHN and showed theoretical results on selecting parameters. On the other hand, Smith et al. proposed the projection CHN which projects a solution onto the feasible region and thus needs not select penalty parameters.

In this paper, we point out some drawbacks of these two models and propose a new CHN with an efficient projection technique for the quadratic assignment problem, which overcomes these drawbacks. Moreover, we show that the proposed model can always find a feasible solution and that it has the local convergence property. Finally, we verify advantages of the proposed model through some numerical experiments.
DEFEASIBLE REASONING IN WEB-BASED FORMS THROUGH ARGUMENTATION
Authors: GÓMEZ SERGIO ALEJANDRO , CHESÑEVAR CARLOS IVÁN , SIMARI GUILLERMO RICARDO
Published: April 2008

The notion of forms as a way of organizing and presenting data has been used since the beginning of the World Wide Web. Web-based forms have evolved together with the development of new markup languages, in which it is possible to provide validation scripts as part of the form code to test whether the intended meaning of the form is correct. However, for the form designer, part of this intended meaning frequently involves other features which are not constraints by themselves, but rather attributes emerging from the form, which provide plausible conclusions in the context of incomplete and potentially inconsistent information. As the value of such attributes may change in presence of new knowledge, we call them defeasible attributes. In this paper, we propose extending traditional web-based forms to incorporate defeasible attributes as part of the knowledge that can be encoded by the form designer. The proposed extension allows the specification of scripts for reasoning about form fields using a defeasible knowledge base, expressed in terms of a Defeasible Logic Program.
A GEOMETRICAL METHOD ON MULTIDIMENSIONAL DYNAMIC CREDIT EVALUATION
Authors: ZHANG YING , CHEN LIN , ZHOU ZONGFANG , SHI YONG
Published: April 2008

In this paper, we first discuss the space frame of multidimensional dynamic credit evaluation (MDCE) theoretically, and then propose the conception of identical credit status and pseudo-identical credit status. Taking advantage of space conformational analysis and optimization techniques, a geometrical method is also founded. By using our method, the credit qualities of all evaluated objects can be ascribed to a suitable credit rating.
First-year students' impressions of pair programming in CS1
Authors: Simon Beth , Hanks Brian
Published: April 2008

Pair programming, as part of the Agile Development process, has noted benefits in professional software development scenarios. These successes have led to a rise in use of pair programming in educational settings, particularly in Computer Science 1 (CS1). Specifically, McDowell et al. [2006] has shown that students using pair programming in CS1 do better in a CS2 class (with solo programming) than students who don't pair in CS1. This paper seeks to address a similar question, but from a qualitative, student-focused approach. How do students define, experience, and value the pair programming experience? How do they experience and value it compared to solo programming? Does pairing in CS1 impact their confidence in their abilities?

We report on semi-structured interviews with 11 subjects from two institutions where pair programming was used in CS1, and solo programming was used in the CS2. Many of the responses met our expectations; students get stuck less and explore more ideas while pairing, and believe that pair programming helped them in CS1. Other responses were more surprising. Students reported that when solo programming they were more confident and understood their programs better. Many students also said that they started work on their assignments earlier when soloing. Students also continue to use other students as resources even when working "solo."
Narrating data structures
Authors: Yarosh Svetlana , Guzdial Mark
Published: April 2008

Learning computing with respect to the context of its use has been linked in previous reports to student motivation in introductory Computer Science (CS) courses. In this report, we consider the role of context in a second course. We present a case study of a CS2 data structures class that uses a media computation context. In this course, students learn data structures and object-oriented (OO) programming through a pervasive narrative about how real media professionals use data structures to model the real world and to construct the digital images, sounds, and animations with which the students are familiar in their daily lives. We found that context played a different role in a second course than in a first course. We found evidence that some students did not need context to appreciate computing, but we also found evidence that context can help students get engaged with the material that they otherwise do not find interesting. In particular, the narrative aspect of a context may help students in relating the elements of the course and may even help with learning.
The priority R-tree
Authors: Arge Lars , Berg Mark De , Haverkort Herman , Yi Ke
Published: April 2008

We present the priority R-tree, or PR-tree, which is the first R-tree variant that always answers a window query using
O
((
N
/
B
)

1−1/
d

+
T
/
B
) I/Os, where
N
is the number of
d
-dimensional (hyper-) rectangles stored in the R-tree,
B
is the disk block size, and
T
is the output size. This is provably asymptotically optimal and significantly better than other R-tree variants, where a query may visit all
N
/
B
leaves in the tree even when
T
= 0. We also present an extensive experimental study of the practical performance of the PR-tree using both real-life and synthetic data. This study shows that the PR-tree performs similarly to the best-known R-tree variants on real-life and relatively nicely distributed data, but outperforms them significantly on more extreme data.
Improved bounds for scheduling conflicting jobs with minsum criteria
Authors: Gandhi Rajiv , Halldórsson Magnús M. , Kortsarz Guy , Shachnai Hadas
Published: April 2008

We consider a general class of scheduling problems where a set of
conflicting
jobs needs to be scheduled (preemptively or nonpreemptively) on a set of machines so as to minimize the weighted sum of completion times. The conflicts among jobs are formed as an
arbitrary
conflict graph.

Building on the framework of Queyranne and Sviridenko [2002b], we present a general technique for reducing the weighted sum of completion-times problem to the classical makespan minimization problem. Using this technique, we improve the best-known results for scheduling conflicting jobs with the min-sum objective, on several fundamental classes of graphs, including line graphs, (
k
+ 1)-claw-free graphs, and perfect graphs. In particular, we obtain the first constant-factor approximation ratio for nonpreemptive scheduling on interval graphs. We also improve the results of Kim [2003] for scheduling jobs on line graphs and for resource-constrained scheduling.
The collective memory of amnesic processes
Authors: Guerraoui Rachid , Levy Ron R. , Pochon Bastian , Pugh Jim
Published: April 2008

This article considers the problem of robustly emulating a shared atomic memory over a distributed message-passing system where processes can fail by crashing and possibly recover. We revisit the notion of atomicity in the crash-recovery context and introduce a generic algorithm that emulates an atomic memory. The algorithm is instantiated for various settings according to whether processes have access to local stable storage, and whether, in every execution of the algorithm, a sufficient number of processes are assumed not to crash. We establish the optimality of specific instances of our algorithm in terms of
resilience
,
log complexity
(number of stable storage accesses needed in every read or write operation), as well as
time complexity
(number of communication steps needed in every read or write operation). The article also discusses the impact of considering a multiwriter versus a single-writer memory, as well as the impact of weakening the consistency of the memory by providing safe or regular semantics instead of atomicity.
Path decomposition under a new cost measure with applications to optical network design
Authors: Anshelevich Elliot , Zhang Lisa
Published: April 2008

We introduce a problem directly inspired by its application to DWDM (
dense wavelength division multiplexing
) network design. We are given a set of demands to be carried over a network. Our goal is to choose a route for each demand and to decompose the network into a collection of edge-disjoint simple paths. These paths are called
optical line systems
. The cost of routing one unit of demand is the number of line systems with which the demand route overlaps; our design objective is to minimize the total cost over all demands. This cost metric is motivated by the need to minimize O-E-O (
optical-electrical-optical
) conversions in optical transmission.

For given line systems, it is easy to find the optimal demand routes. On the other hand, for given demand routes designing the optimal line systems can be NP-hard. We first present a 2-approximation for general network topologies. As optical networks often have low node degrees, we offer an algorithm that finds the optimal solution for the special case in which the node degree is at most 3. Our solution is based on a local greedy approach.

If neither demand routes nor line systems are fixed, the situation becomes much harder. Even for a restricted scenario on a 3-regular Hamiltonian network, no efficient algorithm can guarantee a constant approximation better than 2. For general topologies, we offer a simple algorithm with an
O
(log
K
)- and an
O
(log
n
)-approximation, where
K
is the number of demands and
n
the number of nodes. This approximation ratio is almost tight. For rings, a common special topology, we offer a more complex 3/2-approximation algorithm.
Faith-based security
Authors: Berghel Hal
Published: April 2008

A tongue-in-cheek look at serious security issues.
Measuring consumer satisfaction in internet banking
Authors: Liao Ziqi , Cheung Michael Tow
Published: April 2008

What service-quality attributes must Internet banks offer to induce consumers to switch to online transactions and keep using them?
The provenance of electronic data
Authors: Moreau Luc , Groth Paul , Miles Simon , Vazquez-Salceda Javier , Ibbotson John , Jiang Sheng , Munroe Steve , Rana Omer , Schreiber Andreas , Tan Victor , Varga Laszlo
Published: April 2008

It would include details of the processes that produced electronic data as far back as the beginning of time or at least the epoch of provenance awareness.
Information security and risk management
Authors: Bodin Lawrence D. , Gordon Lawrence A. , Loeb Martin P.
Published: April 2008

Use the new PCR risk metric to find ways to enhance security, avoiding one-dimensional metrics like ALE that could risk an organization's survivability.
"Most Wired Hospitals" rate patient satisfaction
Authors: Whitten Pamela , Mylod Deirdre , Gavran Goran , Sypher Howard
Published: April 2008

Considering the role of IT as a variable in health care institution quality assessment.
The size of the IT job market
Authors: Litecky Chuck , Prabhakar Bipin , Arnett Kirk
Published: April 2008

Comparing the U.S. IT job markets of the 1990s and 2000s.
An adaptative agent architecture for holonic multi-agent systems
Authors: Hilaire Vincent , Koukam Abder , Rodriguez Sebastian
Published: April 2008

Self-organized multi-agent systems (MAS) are still difficult to engineer, because, to deal with real world problems, a self-organized MAS should exhibit complex adaptive organizations. In this respect the holonic paradigm provides a solution for modelling complex organizational structures. Holons are defined as self-similar entities that are neither parts nor wholes. The organizational structure produced by holons is called a holarchy. A holonic MAS (HMAS) considers agents as holons that are grouped according to holarchies. The goal of this article is to introduce an architecture that allows holons to adapt to their environment. The metaphor is based upon the immune system and considers stimulations/requests as antigens and selected antibodies as reactions/answers. Each antibody is activated by specific antigens and stimulated and/or inhibited by other antibodies. The immune system rewards (respectively penalizes) selected antibodies, which constitutes a good (respectively wrong) answer to a request. This mechanism allows an agent to choose from a set of possible behaviors, the one that seems the best fit for a specific context. In this context, each holon, atomic or composed, encapsulates an immune system in order to select a behavior. For composed holons, each sub-holon is represented by the selected antibody of its immune system. The super-holon's immune system therefore contains one antibody per sub-holon. This recursive architecture corresponds with the recursive nature of the holarchy. This architecture is presented with an example of simulated robot soccer. From experiments under different conditions we show that this architecture has interesting properties.
Ant-based distributed constrained steiner tree algorithm for jointly conserving energy and bounding delay in ad hoc multicast routing
Authors: Shen Chien-Chung , Li Ke , Jaikaeo Chaiporn , Sridhara Vinay
Published: April 2008

The minimum-energy multicast tree problem aims to construct a multicast tree rooted at the source node and spanning all the destination nodes such that the sum of transmission power at non-leaf nodes is minimized. However, aggressive power assignment at non-leaf nodes, although conserving more energy, results in multicast trees that suffer from higher hop count and jeopardizes delay-sensitive applications, signifying a clear tradeoff between energy efficiency and delay. This article formulates these issues as a
constrained Steiner tree
problem, and describes a distributed constrained Steiner tree algorithm, which jointly conserves energy and bounds delay for multicast routing in ad hoc networks. In particular, the proposed algorithm concurrently constructs a constrained Steiner tree, performs transmission power assignment at non-leaf nodes, and strives to minimize the sum of transmission power of non-leaf nodes, subject to the given maximum hop count constraint. Simulation results validate the effectiveness and reveal the characteristics of the proposed algorithm.
Admission of QoS aware users in a smart network
Authors: Gelenbe Erol , Sakellari Georgia , D'arienzo Maurizio
Published: April 2008

Smart networks have grown out of the need for stable, reliable, and predictable networks that will guarantee packet delivery under Quality of Service (QoS) constraints. In this article we present a measurement-based admission control algorithm that helps control traffic congestion and guarantee QoS throughout the lifetime of a connection. When a new user requests to enter the network, probe packets are sent from the source to the destination to estimate the impact that the new connection will have on the QoS of both the new and the existing users. The algorithm uses a novel algebra of QoS metrics, inspired by Warshall's algorithm, to look for a path with acceptable QoS values to accommodate the new flow. We describe the underlying mathematical principles and present experimental results obtained by evaluating the method in a large laboratory test-bed operating the Cognitive Packet Network (CPN) protocol.
Down for the count
Authors: Rowell Laurie
Published: April 2008

Major improvements to digital voting systems may lie on the horizon, but the inaccuracies and potential for fraud found in the last U.S. presidential election remain in place.
Content filters
Authors: Weiss Aaron
Published: April 2008

Will ISPs Become the Enforcers of the Web?
SEED
Authors: Du Wenliang , Wang Ronghua
Published: April 2008

The security and assurance of our computing infrastructure has become a national priority. To address this priority, higher education has gradually incorporated the principles of computer and information security into the mainstream undergraduate and graduate computer science curricula. To achieve effective education, learning security principles must be grounded in experience. This calls for effective laboratory exercises (or course projects). Although a number of laboratories have been designed for security education, they only cover a small portion of the fundamental security principles. Moreover, their underlying lab environments are different, making integration of these laboratories infeasible for a semester-long course. Currently, security laboratories that can be widely adopted are still lacking, and they are in great demand in security education.

We have developed a novel laboratory environment (referred to as SEED). The SEED environment consists of Minix, an instructional operating system (OS), and Linux, a production OS; it takes advantage of the simplicity of Minix and the completeness of Linux, and provides a unified platform to support a rich set of laboratories for computer security education. Based on the SEED environment, we have developed a list of laboratories that cover a wide spectrum of security principles. These labs provide opportunities for students to develop essential skills for secure computing practice. We have been using these labs in our courses during the last five years. This article presents our SEED environment, laboratories, and evaluation results.
Up and coming SIGWEB supported conferences and related events
Authors: Lunn Darren
Published: April 2008

SIGWEB supports several specialized conferences, short courses, and workshops, as well as the Annual Hypertext Conference. SIGWEB sponsored conferences focus on timely topics in applied and computational hypertext and Web disciplines and provide a place for members and the entire applied Hypermedia and Web community to exchange ideas and to meet with and expand their network of colleagues. In this article, we provide a brief overview of SIGWEB sponsored conferences, in addition to events that may be of interest, for delegates and other interested parties.
Dependency and interaction oriented complexity metrics of component-based systems
Authors: Gill Nasib S. , Balkishan
Published: April 2008

Component-Based Development (CBD) practice is gaining popularity among software developers in the software industry. Researcher community is striving hard to identify the attributes characterizing component-based development and further proposing metrics that may help in controlling the complexity of the component-based systems. The present paper introduces a set of component-based metrics, namely, Component Dependency Metric (CDM) and Component Interaction Density Metric (CIDM), which measure the dependency and coupling aspects of the software components respectively. Graph theoretic notions have been used to illustrate the dependency and interaction among software components for all the four cases chosen for present study. Dependency and interaction-oriented complexity metrics for component-based systems have been computed. The results of the present study are quite encouraging and may further help the researchers in controlling the complexity of component-based systems so as to minimize the integration and maintenance costs.
JUnit 3.8 documented using collaborations
Authors: Riehle Dirk
Published: April 2008

This paper describes the design of the unit testing framework JUnit v3.8. The documentation technique employed is an enhanced version of collaboration-based design, also known as role modeling. In collaboration-based design, objects are viewed as playing multiple roles in different contexts, and different contexts are viewed as task specific collaborations. The documentation accounts for every method in the JUnit 3.8 framework by assigning it to a role. It thereby investigates whether roles and collaborations can serve as basic units of functionality provided by a design like a framework. Such a measure of functionality can serve multiple purposes, for example estimating implementation efforts or measuring complexity.
SoftSig
Authors: Tuck James , Ahn Wonsun , Ceze Luis , Torrellas Josep
Published: April 2008

Many code analysis techniques for optimization, debugging, or parallelization need to perform runtime disambiguation of sets of addresses. Such operations can be supported efficiently and with low complexity with hardware signatures.

To enable flexible use of signatures, this paper proposes to expose a Signature Register File to the software through a rich ISA. The software has great flexibility to decide, for each signature,which addresses to collect and which addresses to disambiguate against. We call this architecture
SoftSig
. In addition, as an example of SoftSig use, we show how to detect redundant function calls efficiently and eliminate them dynamically. We call this algorithm
MemoiSE
. On average for five popular applications, MemoiSE reduces the number of dynamic instructions by 9.3%, thereby reducing the execution time of the applications by 9%.
Understanding and visualizing full systems with data flow tomography
Authors: Mysore Shashidhar , Mazloom Bita , Agrawal Banit , Sherwood Timothy
Published: April 2008

It is not uncommon for modern systems to be composed of a variety of interacting services, running across multiple machines in such a way that most developers do not really understand the whole system. As abstraction is layered atop abstraction, developers gain the ability to compose systems of extraordinary complexity with relative ease. However, many software properties, especially those that cut across abstraction layers, become very difficult to understand in such compositions. The communication patterns involved, the privacy of critical data, and the provenance of information, can be difficult to find and understand, even with access to all of the source code. The goal of Data Flow Tomography is to use the inherent information flow of such systems to help visualize the interactions between complex and interwoven components across multiple layers of abstraction. In the same way that the injection of short-lived radioactive isotopes help doctors trace problems in the cardiovascular system, the use of "data tagging" can help developers slice through the extraneous layers of software and pin-point those portions of the system interacting with the data of interest. To demonstrate the feasibility of this approach we have developed a prototype system in which tags are tracked both through the machine and in between machines over the network, and from which novel visualizations of the whole system can be derived. We describe the system-level challenges in creating a working system tomography tool and we qualitatively evaluate our system by examining several example real world scenarios.
Merge
Authors: Linderman Michael D. , Collins Jamison D. , Wang Hong , Meng Teresa H.
Published: April 2008

In this paper we propose the Merge framework, a general purpose programming model for heterogeneous multi-core systems. The Merge framework replaces current ad hoc approaches to parallel programming on heterogeneous platforms with a rigorous, library-based methodology that can automatically distribute computation across heterogeneous cores to achieve increased energy and performance efficiency. The Merge framework provides (1) a predicate dispatch-based library system for managing and invoking function variants for multiple architectures; (2) a high-level, library-oriented parallel language based on map-reduce; and (3) a compiler and runtime which implement the map-reduce language pattern by dynamically selecting the best available function implementations for a given input and machine configuration. Using a generic sequencer architecture interface for heterogeneous accelerators, the Merge framework can integrate function variants for specialized accelerators, offering the potential for to-the-metal performance for a wide range of heterogeneous architectures, all transparent to the user. The Merge framework has been prototyped on a heterogeneous platform consisting of an Intel Core 2 Duo CPU and an 8-core 32-thread Intel Graphics and Media Accelerator X3000, and a homogeneous 32-way Unisys SMP system with Intel Xeon processors. We implemented a set of benchmarks using the Merge framework and enhanced the library with X3000 specific implementations, achieving speedups of 3.6x -- 8.5x using the X3000 and 5.2x -- 22x using the 32-way system relative to the straight C reference implementation on a single IA32 core.
Streamware
Authors: Gummaraju Jayanth , Coburn Joel , Turner Yoshio , Rosenblum Mendel
Published: April 2008

Recently, the number of cores on general-purpose processors has been increasing rapidly. Using conventional programming models, it is challenging to effectively exploit these cores for maximal performance. An interesting alternative candidate for programming multiple cores is the stream programming model, which provides a framework for writing programs in a sequential-style while greatly simplifying the task of automatic parallelization. It has been shown that not only traditional media/image applications but also more general-purpose data-intensive applications can be expressed in the stream programming style.

In this paper, we investigate the potential to use the stream programming model to efficiently utilize commodity multicore general-purpose processors (e.g., Intel/AMD). Although several stream languages and stream compilers have recently been developed, they typically target special-purpose stream processors. In contrast, we propose a flexible software system, Streamware, which automatically maps stream programs onto a wide variety of general-purpose multicore processor configurations. We leverage existing compilation framework for stream processors and design a runtime environment which takes as input the output of these stream compilers in the form of machine-independent stream virtual machine code. The runtime environment assigns work to processor cores considering processor/cache configurations and adapts to workload variations. We evaluate this approach for a few general-purpose scientific applications on real hardware and a cycle-level simulator set-up to showcase scaling and contention issues. The results show that the stream programming model is a good choice for efficiently exploiting modern and future multicore CPUs for an important class of applications.
The mapping collector
Authors: Wegiel Michal , Krintz Chandra
Published: April 2008

Parallel and concurrent garbage collectors are increasingly employed by managed runtime environments (MREs) to maintain scalability, as multi-core architectures and multi-threaded applications become pervasive. Moreover, state-of-the-art MREs commonly implement compaction to eliminate heap fragmentation and enable fast linear object allocation.

Our empirical analysis of object demographics reveals that unreachable objects in the heap tend to form clusters large enough to be effectively managed at the granularity of virtual memory pages. Even though processes can manipulate the mapping of the virtual address space through the standard operating system (OS) interface on most platforms, extant parallel/concurrent compactors do not do so to exploit this clustering behavior and instead achieve compaction by performing, relatively expensive, object moving and pointer adjustment.

We introduce the Mapping Collector (MC), which leverages virtual memory operations to reclaim and consolidate free space without moving objects and updating pointers. MC is a nearly-single-phase compactor that is simpler and more efficient than previously reported compactors that comprise two to four phases. Through effective MRE-OS coordination, MC maintains the simplicity of a non-moving collector while providing efficient parallel and concurrent compaction.

We implement both stop-the-world and concurrent MC in a generational garbage collection framework within the open-source HotSpot Java Virtual Machine. Our experimental evaluation using a multiprocessor indicates that MC significantly increases throughput and scalability as well as reduces pause times, relative to state-of-the-art, parallel and concurrent compactors.
Dispersing proprietary applications as benchmarks through code mutation
Authors: Van Ertvelde Luk , Eeckhout Lieven
Published: April 2008

Industry vendors hesitate to disseminate proprietary applications to academia and third party vendors. By consequence, the benchmarking process is typically driven by standardized, open-source benchmarks which may be very different from and likely not representative of the real-life applications of interest.

This paper proposes code mutation, a novel technique that mutates a proprietary application to complicate reverse engineering so that it can be distributed as a benchmark. The benchmark mutant then serves as a proxy for the proprietary application. The key idea in the proposed code mutation approach is to preserve the proprietary application's dynamic memory access and/or control flow behavior in the benchmark mutant while mutating the rest of the application code. To this end, we compute program slices for memory access operations and/or control flow operationstrimmed through constant value and branch profiles; and subsequently mutate the instructions not appearing in these slices through binary rewriting.

Our experimental results using SPEC CPU2000 and MiBench benchmarks show that code mutation is a promising technique that mutates up to 90% of the static binary, up to 50% of the dynamically executed instructions, and up to 35% of the at run time exposed inter-operation data dependencies. The performance characteristics of the mutant are very similar to those of the proprietary application across a wide range of microarchitectures and hardware implementations.
Better bug reporting with better privacy
Authors: Castro Miguel , Costa Manuel , Martin Jean-Philippe
Published: April 2008

Software vendors collect bug reports from customers to improve the quality of their software. These reports should include the inputs that make the software fail, to enable vendors to reproduce the bug. However, vendors rarely include these inputs in reports because they may contain private user data. We describe a solution to this problem that provides software vendors with new input values that satisfy the conditions required to make the software follow the same execution path until it fails, but are otherwise unrelated with the original inputs. These new inputs allow vendors to reproduce the bug while revealing less private information than existing approaches. Additionally, we provide a mechanism to measure the amount of information revealed in an error report. This mechanism allows users to perform informed decisions on whether or not to submit reports. We implemented a prototype of our solution and evaluated it with real errors in real programs. The results show that we can produce error reports that allow software vendors to reproduce bugs while revealing almost no private information.
Learning from mistakes
Authors: Lu Shan , Park Soyeon , Seo Eunsoo , Zhou Yuanyuan
Published: April 2008

The reality of multi-core hardware has made concurrent programs pervasive. Unfortunately, writing correct concurrent programs is difficult. Addressing this challenge requires advances in multiple directions, including concurrency bug detection, concurrent program testing, concurrent programming model design, etc. Designing effective techniques in all these directions will significantly benefit from a deep understanding of real world concurrency bug characteristics.

This paper provides the first (to the best of our knowledge) comprehensive real world concurrency bug characteristic study. Specifically, we have carefully examined concurrency bug patterns, manifestation, and fix strategies of 105 randomly selected real world concurrency bugs from 4 representative server and client open-source applications (MySQL, Apache, Mozilla and OpenOffice). Our study reveals several interesting findings and provides useful guidance for concurrency bug detection, testing, and concurrent programming language design.

Some of our findings are as follows: (1) Around one third of the examined non-deadlock concurrency bugs are caused by violation to programmers' order intentions, which may not be easily expressed via synchronization primitives like locks and transactional memories; (2) Around 34% of the examined non-deadlock concurrency bugs involve multiple variables, which are not well addressed by existing bug detection tools; (3) About 92% of the examined concurrency bugs canbe reliably triggered by enforcing certain orders among no more than 4 memory accesses. This indicates that testing concurrent programs can target at exploring possible orders among every small groups of memory accesses, instead of among all memory accesses; (4) About 73% of the examinednon-deadlock concurrency bugs were not fixed by simply adding or changing locks, and many of the fixes were not correct at the first try, indicating the difficulty of reasoning concurrent execution by programmers.
Toward molecular programming with DNA
Authors: Winfree Erik
Published: April 2008

Biological organisms are beautiful examples of programming. The program and data are stored in biological molecules such as DNA, RNA, and proteins; the algorithms are carried out by molecular and biochemical processes; and the end result is the creation and function of an organism. If we understood how to program molecular systems, what could we create? Lifelike technologies whose basic operations are chemical reactions? The fields of chemistry, physics, biology, and computer science are converging as we begin to synthesize molecules, molecular machines, and molecular systems of ever increasing complexity, leading to subdisciplines such as DNA nanotechnology, DNA computing, and synthetic biology. Having demonstrated simple devices and systems -- self-assembled structures, molecular motors, chemical logic gates -- researchers are now turning to the question of how to create large-scale integrated systems. To do so, we must learn how to manage complexity: how to efficiently specify the structure and behavior of intricate molecular systems, how to compile such specifications down to the design of molecules to be synthesized in the lab, and how to ensure that such systems function robustly. These issues will be illustrated for chemical logic circuits based on cascades of DNA hybridization reactions.

Bio

Erik Winfree is an Associate Professor in Computer Science, Computation & Neural Systems, and Bioengineering at Caltech. Winfree is the recipient of the Feynman Prize for Nanotechnology (2006), the NSF PECASE/CAREER Award (2001), the ONR Young Investigators Award (2001), a MacArthur Fellowship (2000), and MIT Technology Review's first TR100 list of "top young innovators" (1999). Prior to joining the faculty at Caltech in 2000, Winfree was a Lewis Thomas Postdoctoral Fellow in Molecular Biology at Princeton, and a Visiting Scientist at the MIT AI Lab. Winfree received a B.S. in Mathematics w/ Computer Science from the University of Chicago in 1991, and a Ph.D. in Computation & Neural Systems from Caltech in 1998. His website is http://dna.caltech.edu/~winfree/.
The design and implementation of microdrivers
Authors: Ganapathy Vinod , Renzelmann Matthew J. , Balakrishnan Arini , Swift Michael M. , Jha Somesh
Published: April 2008

Device drivers commonly execute in the kernel to achieve high performance and easy access to kernel services. However, this comes at the price of decreased reliability and increased programming difficulty. Driver programmers are unable to use user-mode development tools and must instead use cumbersome kernel tools. Faults in kernel drivers can cause the entire operating system to crash. User-mode drivers have long been seen as a solution to this problem, but suffer from either poor performance or new interfaces that require a rewrite of existing drivers.

This paper introduces the Microdrivers architecture that achieves high performance and compatibility by leaving critical path code in the kernel and moving the rest of the driver code to a user-mode process. This allows data-handling operations critical to I/O performance to run at full speed, while management operations such as initialization and configuration run at reduced speed in user-level. To achieve compatibility, we present DriverSlicer, a tool that splits existing kernel drivers into a kernel-level component and a user-level component using a small number of programmer annotations. Experiments show that as much as 65% of driver code can be removed from the kernel without affecting common-case performance, and that only 1-6 percent of the code requires annotations.
Exercises and problems
Authors: Polivka Ray
Published: April 2008

The answer to the sums of the diagonals of a 1001 by 1001 spiral matrix is 669,171,001. More interesting than the answer is the number of responses and the variety of solutions. Beside solutions from APL and J, I received solutions using C++, RoboBasic, and EXCEL. Several submitters used their observations to produce mathematical solutions. Some of the mathematical solutions resulted in different equations. I'll try to summarize all the submissions.
Rethinking virtual network embedding
Authors: Yu Minlan , Yi Yung , Rexford Jennifer , Chiang Mung
Published: April 2008

Network virtualization is a powerful way to run multiple architectures or experiments simultaneously on a shared infrastructure. However, making efficient use of the underlying resources requires effective techniques for virtual network embedding--mapping each virtual network to specific nodes and links in the substrate network. Since the general embedding problem is computationally intractable, past research restricted the problem space to allow efficient solutions, or focused on designing heuristic algorithms. In this paper, we advocate a different approach: rethinking the design of the substrate network to enable simpler embedding algorithms and more efficient use of resources, without restricting the problem space. In particular, we simplify virtual link embedding by: i) allowing the substrate network to split a virtual link over multiple substrate paths and ii) employing path migration to periodically re-optimize the utilization of the substrate network. We also explore node-mapping algorithms that are customized to common classes of virtual-network topologies. Our simulation experiments show that path splitting, path migration,and customized embedding algorithms enable a substrate network to satisfy a much larger mix of virtual networks
New directions in mobile communications, or how to learn to stop hating the cellular telephone industry
Authors: Crowcroft Jon
Published: April 2008

In this article, we discuss the lessons in innovation from the last twenty years of the Internet that might be applied in the cellular telephone industry.
The future in your pocket
Authors: Crowley Patrick
Published: April 2008

There is a growing sentiment among academics in computing that a shift to multicore processors in commodity computers will demand that all programmers become parallel programmers. This is because future general-purpose processors are not likely to improve the performance of a single thread of execution; instead, the presence of multiple processor cores on a CPU will improve the performance of groups of threads. In this article, I argue that there is another trend underway, namely integration, which will have a greater near-term impact on developers of system software and applications. This integration, and its likely impact on general-purpose computers, is clearly illustrated in the architecture of modern mobile phones
Effect of destrin mutations on the gene expression profile in vivo
Authors: Verdoni Angela M. , Aoyama Natsuyo , Ikeda Akihiro , Ikeda Sakae
Published: April 2008

Remodeling of the actin cytoskeleton through actin dynamics (assembly and disassembly of filamentous actin) is known to be essential for numerous basic biological processes. In addition, recent studies have provided evidence that actin dynamics participate in the control of gene expression. A spontaneous mouse mutant, corneal disease 1 ( corn1), is deficient for a regulator of actin dynamics, destrin (DSTN, also known as ADF), which causes epithelial hyperproliferation and neovascularization in the cornea. Dstn corn1 mice exhibit an actin dynamics defect in the corneal epithelial cells, offering an in vivo model to investigate cellular mechanisms affected by the Dstn mutation and resultant actin dynamics abnormalities. To examine the effect of the Dstn corn1 mutation on the gene expression profile, we performed a microarray analysis using the cornea from Dstn corn1 and wild-type mice. A dramatic alteration of the gene expression profile was observed in the Dstn corn1 cornea, with 1,226 annotated genes differentially expressed. Functional annotation of these genes revealed that the most significantly enriched functional categories are associated with actin and/or cytoskeleton. Among genes that belong to these categories, a considerable number of serum response factor target genes were found, indicating the possible existence of an actin-SRF pathway of transcriptional regulation in vivo. A comparative study using an allelic mutant strain with milder corneal phenotypes suggested that the level of filamentous actin may correlate with the level of gene expression changes. Our study shows that Dstn mutations and resultant actin dynamics abnormalities have a strong impact on the gene expression profile in vivo.
Blood Vessel Maturation and Response to Vascular-Disrupting Therapy in Single Vascular Endothelial Growth Factor-A Isoform–Producing Tumors
Authors: Tozer Gillian M. , Akerman Simon , Cross Neil A. , Barber Paul R. , Björndahl Meit A. , Greco Olga , Harris Sheila , Hill Sally A. , Honess Davina J. , Ireson Christopher R. , Pettyjohn Katie L. , Prise Vivien E. , Reyes-Aldasoro Constantino C. , Ruhrberg Christiana , Shima David T. , Kanthou Chryso
Published: April 2008

Tubulin-binding vascular-disrupting agents (VDA) are currently in clinical trials for cancer therapy but the factors that influence tumor susceptibility to these agents are poorly understood. We evaluated the consequences of modifying tumor vascular morphology and function on vascular and therapeutic response to combretastatin-A4 3-O-phosphate (CA-4-P), which was chosen as a model VDA. Mouse fibrosarcoma cell lines that are capable of expressing all vascular endothelial growth factor (VEGF) isoforms (control) or only single isoforms of VEGF (VEGF120, VEGF164, or VEGF188) were developed under endogenous VEGF promoter control. Once tumors were established, VEGF isoform expression did not affect growth or blood flow rate. However, VEGF188 was uniquely associated with tumor vascular maturity, resistance to hemorrhage, and resistance to CA-4-P. Pericyte staining was much greater in VEGF188 and control tumors than in VEGF120 and VEGF164 tumors. Vascular volume was highest in VEGF120 and control tumors (CD31 staining) but total vascular length was highest in VEGF188 tumors, reflecting very narrow vessels forming complex vascular networks. I.v. administered 40 kDa FITC-dextran leaked slowly from the vasculature of VEGF188 tumors compared with VEGF120 tumors. Intravital microscopy measurements of vascular length and RBC velocity showed that CA-4-P produced significantly more vascular damage in VEGF120 and VEGF164 tumors than in VEGF188 and control tumors. Importantly, this translated into a similar differential in therapeutic response, as determined by tumor growth delay. Results imply differences in signaling pathways between VEGF isoforms and suggest that VEGF isoforms might be useful in vascular-disrupting cancer therapy to predict tumor susceptibility to VDAs. [Cancer Res 2008;68(7):2301–11]
Risk Stratification in Cancer Predisposition Syndromes: Lessons Learned from Novel Molecular Developments in Li-Fraumeni Syndrome
Authors: Tabori Uri , Malkin David
Published: April 2008

Germ-line mutations in specific genes predispose family members to cancer. Prediction of the exact tumor type and timing of cancer initiation is fundamental to the development of management strategies for these individuals. Recent advances in our understanding of the general processes that control cancer initiation may enable us to tailor more precise risk stratification. This, in turn, will lead to more effective early detection strategies, which would result in more favorable clinical outcomes. In this review, we highlight the steps and methods used to reach this futuristic model. [Cancer Res 2008;68(7):2053–7]