bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital filters in adaptive time-stepping
Authors: Söderlind Gustaf
Published: May 2003

Adaptive time-stepping based on linear digital control theory has several advantages: the algorithms can be analyzed in terms of stability and adaptivity, and they can be designed to produce smoother stepsize sequences resulting in significantly improved regularity and computational stability. Here, we extend this approach by viewing the closed-loop transfer map
H
φ
: logφ ↦ log
h
as a digital filter, processing the signal logφ (the principal error function) in the frequency domain, in order to produce a smooth stepsize sequence log
h
. The theory covers all previously considered control structures and offers new possibilities to construct stepsize selection algorithms in the asymptotic stepsize-error regime. Without incurring extra computational costs, the controllers can be designed for special purposes such as higher order of adaptivity (for smooth ODE problems) or a stronger ability to suppress high-frequency error components (nonsmooth problems, stochastic ODEs). Simulations verify the controllers' ability to produce stepsize sequences resulting in improved regularity and computational stability.
Scalar fused multiply-add instructions produce floating-point matrix arithmetic provably accurate to the penultimate digit
Authors: Nievergelt Yves
Published: May 2003

Combined with doubly compensated summation, scalar fused multiply-add instructions redefine the concept of floating-point arithmetic, because they allow for the computation of sums of real or complex matrix products accurate to the penultimate digit. Particular cases include complex arithmetic, dot products, cross products, residuals of linear systems, determinants of small matrices, discriminants of quadratic, cubic, or quartic equations, and polynomials.
Object-oriented software for quadratic programming
Authors: Gertz E. Michael , Wright Stephen J.
Published: May 2003

The object-oriented software package OOQP for solving convex quadratic programming problems (QP) is described. The primal-dual interior point algorithms supplied by OOQP are implemented in a way that is largely independent of the problem structure. Users may exploit problem structure by supplying linear algebra, problem data, and variable classes that are customized to their particular applications. The OOQP distribution contains default implementations that solve several important QP problem types, including general sparse and dense QPs, bound-constrained QPs, and QPs arising from support vector machines and Huber regression. The implementations supplied with the OOQP distribution are based on such well known linear algebra packages as MA27/57, LAPACK, and PETSc. OOQP demonstrates the usefulness of object-oriented design in optimization software development, and establishes standards that can be followed in the design of software packages for other classes of optimization problems. A number of the classes in OOQP may also be reusable directly in other codes.
Intensional analysis of quantified types
Authors: Saha Bratin , Trifonov Valery , Shao Zhong
Published: May 2003

Compilers for polymorphic languages can use run-time type inspection to support advanced implementation techniques such as tagless garbage collection, polymorphic marshalling, and flattened data structures. Intensional type analysis is a type-theoretic framework for expressing and certifying such type-analyzing computations. Unfortunately, existing approaches to intensional analysis do not work well on quantified types such as existential or polymorphic types. This makes it impossible to code (in a type-safe language) applications such as garbage collection, persistency, or marshalling which must be able to examine the type of any run-time value. We present a typed intermediate language that supports the analysis of quantified types. In particular, we provide both type-level and term-level constructs for analyzing quantified types. Our system supports structural induction on quantified types yet type-checking remains decidable. We also show that our system is compatible with a type-erasure semantics.
PolyTOIL
Authors: Bruce Kim B. , Schuett Angela , van Gent Robert , Fiech Adrian
Published: May 2003

PolyTOIL is a new statically typed polymorphic object-oriented programming language that is provably typesafe. By separating the definitions of subtyping and inheritance, providing a name for the type of self, and carefully defining the type-checking rules, we have obtained a language that is very expressive while supporting modular type-checking of classes. Thematchingrelation on types, which is related to F-bounded quantification, is used both in stating type-checking rules and expressing the bounds on type parameters for polymorphism. The design of PolyTOIL is based on a careful formal definition of type-checking rules and semantics. A proof of type safety is obtained with the aid of a subject reduction theorem.
A foundation for embedded languages
Authors: Rhiger Morten
Published: May 2003

Recent work on embedding object languages into Haskell use "phantom types" (i.e., parameterized types whose parameter does not occur on the right-hand side of the type definition) to ensure that the embedded object-language terms are simply typed. But is it a safe assumption that
only
simply-typed terms can be represented in Haskell using phantom types? And conversely, can
all
simply-typed terms be represented in Haskell under the restrictions imposed by phantom types? In this article we investigate the conditions under which these assumptions are true: We show that these questions can be answered affirmatively for an idealized Haskell-like language and discuss to which extent Haskell can be used as a meta-language.
Stack inspection
Authors: Fournet Cédric , Gordon Andrew D.
Published: May 2003

Stack inspection is a security mechanism implemented in runtimes such as the JVM and the CLR to accommodate components with diverse levels of trust. Although stack inspection enables the fine-grained expression of access control policies, it has rather a complex and subtle semantics. We present a formal semantics and an equational theory to explain how stack inspection affects program behavior and code optimisations. We discuss the security properties enforced by stack inspection, and also consider variants with stronger, simpler properties.
Parallel simulation of chip-multiprocessor architectures
Authors: Chidester Matthew , George Alan
Published: May 2003

Chip-multiprocessor (CMP) architectures present a challenge for efficient simulation, combining the requirements of a detailed microprocessor simulator with that of a tightly-coupled parallel system. In this paper, a distributed simulator for target CMPs is presented based on the Message Passing Interface (MPI) designed to run on a host cluster of workstations. Microbenchmark-based evaluation is used to narrow the parallelization design space concerning the performance impact of distributed vs. centralized target L2 simulation, blocking vs. non-blocking remote cache accesses, null-message vs. barrier techniques for clock synchronization, and network interconnect selection. The best combination is shown to yield speedups of up to 16 on a 9-node cluster of dual-CPU workstations, partially due to cache effects.
A two-stage modeling and simulation process for web-based modeling and simulation
Authors: Kim Taewoo , Lee Jinho , Fishwick Paul
Published: May 2003

The area of web-based simulation has thrived primarily on novel methods for executing models, with contributions to both client and server side applications based in Java and other web-accessible languages. However, there has not been a commensurate degree of research in the area of model design, and in the dissemination of models over the web to support discrete event simulation. For a web-based modeling framework to succeed, that framework must support at least one markup language for specifying model content, as well as methods for converting the markup to a programming language, which is used to simulate the model. We present such a framework, calledrube, and focus on a two-stage translation process from one markup language (MXL) to another (DXL), with a final process to create either Java or Javascript target code. This framework has allowed us to leverage the eXtensible Markup Language (XML) for capturing the dynamics of a small number of key modeling types commonly found in computer simulation applications. Our approach allows us to achieve customization of a model's appearance, as well to obtain the transformative benefits of specifying model information within an XML format.
Metamodeling in EIA/CDIF---meta-metamodel and metamodels
Authors: Flatscher Rony G.
Published: May 2003

This article introduces the EIA/CDIF set of standards for the modeling of information systems and its exchange among computer-aided software tools of different vendors. It lays out the meta-metamodel and the standardized metamodels which are fully depicted in a hierarchical layout and annotated with the unique identifiers of all the standardized modeling concepts. The article also stresses the fact that EIA/CDIF has been used as the baseline in the creation of an international standard, the ISO/CDIF set of models, an ongoing project.
A component-based approach to modeling and simulating mixed-signal and hybrid systems
Authors: Liu Jie , Lee Edward A.
Published: May 2003

Systems with both continuous and discrete behaviors can be modeled using a mixed-signal style or a hybrid systems style. This article presents a component-based modeling and simulation framework that supports both modeling styles. The component framework, based on an actor metamodel, takes a hierarchical approach to manage heterogeneity in modeling complex systems. We describe how ordinary differential equations, discrete event systems, and finite-state machines can be built under this metamodel. A mixed-signal system is a hierarchical composition of continuous-time and discrete event models, and a hybrid system is a hierarchical composition of continuous-time and finite-state-machine models. Hierarchical composition and information hiding help build clean models and efficient execution engines. Simulation technologies, in particular, the interaction between a continuous-time ODE solving engine and various discrete simulation engines are discussed. A signal type system is introduced to schedule hybrid components inside a continuous-time environment. Breakpoints are used to control the numerical integration step sizes so that discrete events are handled properly. A "refiring" mechanism and a "rollback" mechanism are designed to manage continuous components inside a discrete event environment. The technologies are implemented in the Ptolemy II software environment. Examples are given to show the applications of this framework in mixed-signal and hybrid systems.
Web mining for web personalization
Authors: Eirinaki Magdalini , Vazirgiannis Michalis
Published: May 2003

Web personalization is the process of customizing a Web site to the needs of specific users, taking advantage of the knowledge acquired from the analysis of the user's navigational behavior (usage data) in correlation with other information collected in the Web context, namely, structure, content, and user profile data. Due to the explosive growth of the Web, the domain of Web personalization has gained great momentum both in the research and commercial areas. In this article we present a survey of the use of Web mining for Web personalization. More specifically, we introduce the modules that comprise a Web personalization system, emphasizing the Web usage mining module. A review of the most common methods that are used as well as technical issues that occur is given, along with a brief overview of the most popular tools and applications available from software vendors. Moreover, the most important research initiatives in the Web usage mining and personalization areas are presented.
(How) can mobile agents do secure electronic transactions on untrusted hosts? A survey of the security issues and the current solutions
Authors: Claessens Joris , Preneel Bart , Vandewalle Joos
Published: May 2003

This article investigates if and how mobile agents can execute secure electronic transactions on untrusted hosts. An overview of the security issues of mobile agents is first given. The problem of untrusted (i.e., potentially malicious) hosts is one of these issues, and appears to be the most difficult to solve. The current approaches to counter this problem are evaluated, and their relevance for secure electronic transactions is discussed. In particular, a state-of-the-art survey of mobile agent-based secure electronic transactions is presented.
Design and development of data-intensive web sites
Authors: Merialdo Paolo , Atzeni Paolo , Mecca Giansalvatore
Published: May 2003

Data-intensive Web sites are large sites based on a back-end database, with a fairly complex hypertext structure. The paper develops two main contributions: (a) a specific design methodology for data-intensive Web sites, composed of a set of steps and design transformations that lead from a conceptual specification of the domain of interest to the actual implementation of the site; (b) a tool called H
omer
, conceived to support the site design and implementation process, by allowing the designer to move through the various steps of the methodology, and to automate the generation of the code needed to implement the actual site.Our approach to site design is based on a clear separation between several design activities, namely database design, hypertext design, and presentation design. All these activities are carried on by using high-level models, all subsumed by an extension of the nested relational model; the mappings between the models can be nicely expressed using an extended relational algebra for nested structures. Based on the design artifacts produced during the design process, and on their representation in the algebraic framework, H
omer
is able to generate all the code needed for the actual generation of the site, in a completely automatic way.
Description logics for semantic query optimization in object-oriented database systems
Authors: Beneventano Domenico , Bergamaschi Sonia , Sartori Claudio
Published: May 2003

Semantic query optimization uses semantic knowledge (i.e., integrity constraints) to transform a query into an equivalent one that may be answered more efficiently. This article proposes a general method for semantic query optimization in the framework of Object-Oriented Database Systems. The method is effective for a large class of queries, including conjunctive recursive queries expressed with regular path expressions and is based on three ingredients. The first is a Description Logic, ODL
RE
, providing a type system capable of expressing: class descriptions, queries, views, integrity constraint rules and inference techniques, such as
incoherence
detection and
subsumption
computation. The second is a semantic expansion function for queries, which incorporates restrictions logically implied by the query and the schema (classes + rules) in one query. The third is an optimal rewriting method of a query with respect to the schema classes that rewrites a query into an equivalent one, by determining more specialized classes to be accessed and by reducing the number of factors. We implemented the method in a tool providing an ODMG-compliant interface that allows a full interaction with OQL queries, wrapping underlying Description Logic representation and techniques to the user.
A simple algorithm for finding frequent elements in streams and bags
Authors: Karp Richard M. , Shenker Scott , Papadimitriou Christos H.
Published: May 2003

We present a simple, exact algorithm for identifying in a multiset the items with frequency more than a threshold θ. The algorithm requires two passes, linear time, and space 1/θ. The first pass is an on-line algorithm, generalizing a well-known algorithm for finding a majority element, for identifying a set of at most 1/θ items that includes, possibly among others, all items with frequency greater than θ.
Adaptive algorithms for set containment joins
Authors: Melnik Sergey , Garcia-Molina Hector
Published: May 2003

A set containment join is a join between set-valued attributes of two relations, whose join condition is specified using the subset (⊆) operator. Set containment joins are deployed in many database applications, even those that do not support set-valued attributes. In this article, we propose two novel partitioning algorithms, called the Adaptive Pick-and-Sweep Join (APSJ) and the Adaptive Divide-and-Conquer Join (ADCJ), which allow computing set containment joins efficiently. We show that APSJ outperforms previously suggested algorithms for many data sets, often by an order of magnitude. We present a detailed analysis of the algorithms and study their performance on real and synthetic data using an implemented testbed.
BlueBoX
Authors: Chari Suresh N. , Cheng Pau-Chen
Published: May 2003

Detecting attacks against systems has, in practice, largely been delegated to sensors, such as network intrustion detection systems. However, due to the inherent limitations of these systems and the increasing use of encryption in communication, intrusion detection and prevention have once again moved back to the host systems themselves. In this paper, we describe our experiences with building BlueBox, a host-based intrusion detection system. Our approach, based on the technique of system call introspection, can be viewed as creating an infrastructure for defining and enforcing very fine-grained process capabilities in the kernel. These capabilities are specified as a set of rules (policies) for regulating access to system resources on a per executable basis. The language for expressing the rules is intuitive and sufficiently expressive to effectively capture security boundaries.We have prototyped our approach on Linux operating system kernel and have built rule templates for popular daemons such as Apache and wu-ftpd. Our design has been validated by testing against a comprehensive database of known attacks. Our system has been designed to minimize the kernel changes and performance impact and thus can be ported easily to new kernels. We describe the motivation and rationale behind BlueBox, its design, implementation on Linux, and how it relates to prior work on detecting and preventing intrusions on host systems.
Administrative scope
Authors: Crampton Jason , Loizou George
Published: May 2003

We introduce the concept of administrative scope in a role hierarchy and demonstrate that it can be used as a basis for role-based administration. We then develop a family of models for role hierarchy administration (RHA) employing administrative scope as the central concept. We then extend RHA
4
, the most complex model in the family, to a complete, decentralized model for role-based administration. We show that SARBAC, the resulting role-based administrative model, has significant practical and theoretical advantages over ARBAC97. We also discuss how administrative scope might be applied to the administration of general hierarchical structures, how our model can be used to reduce inheritance in the role hierarchy, and how it can be configured to support discretionary access control features.
Access control with IBM Tivoli access manager
Authors: Karjoth Günter
Published: May 2003

Web presence has become a key consideration for the majority of companies and other organizations. Besides being an essential information delivery tool, the Web is increasingly being regarded as an extension of the organization itself, directly integrated with its operating processes. As this transformation takes place, security grows in importance. IBM Tivoli Access Manager offers a shared infrastructure for authentication and access management, technologies that have begun to emerge in the commercial marketplace. This paper describes the Authorization Service provided by IBM Tivoli Access Manager for e-business (AM) and its use by AM family members as well as third-party applications. Policies are defined over a protected object namespace and stored in a database, which is managed via a management console and accessed through an Authorization API. The protected object namespace abstracts from heterogeneous systems and thus enables the definition of consistent policies and their centralized management. ACL inheritance and delegated management allow these policies to be managed efficiently. The Authorization API allows applications with their own access control requirements to decouple authorization logic from application logic. Policy checking can be externalized by using either a proxy that sits in front of the Web servers and application servers or a plug-in that examines the request. Thus, AM familiy members establish a single entry point to enforce enterprise policies that regulate access to corporate data.
Astrolabe
Authors: Van Renesse Robbert , Birman Kenneth P. , Vogels Werner
Published: May 2003

Scalable management and self-organizational capabilities are
emerging as central requirements for a generation of large-scale,
highly dynamic, distributed applications. We have developed an
entirely new distributed information management system called
Astrolabe. Astrolabe collects large-scale system state, permitting
rapid updates and providing on-the-fly attribute aggregation. This
latter capability permits an application to locate a resource, and
also offers a scalable way to track system state as it evolves over
time. The combination of features makes it possible to solve a wide
variety of management and self-configuration problems. This paper
describes the design of the system with a focus upon its
scalability. After describing the Astrolabe service, we present
examples of the use of Astrolabe for locating resources,
publish-subscribe, and distributed synchronization in large
systems. Astrolabe is implemented using a peer-to-peer protocol,
and uses a restricted form of mobile code based on the SQL query
language for aggregation. This protocol gives rise to a novel
consistency model. Astrolabe addresses several security
considerations using a built-in PKI. The scalability of the system
is evaluated using both simulation and experiments; these confirm
that Astrolabe could scale to thousands and perhaps millions of
nodes, with information propagation delays in the tens of seconds.
Size-based scheduling to improve web performance
Authors: Harchol-Balter Mor , Schroeder Bianca , Bansal Nikhil , Agrawal Mukesh
Published: May 2003

Is it possible to reduce the expected response time of
every
request at a web server, simply by changing the order in which we schedule the requests? That is the question we ask in this paper.This paper proposes a method for improving the performance of web servers servicing static HTTP requests. The idea is to give preference to requests for small files or requests with short remaining file size, in accordance with the SRPT (Shortest Remaining Processing Time) scheduling policy.The implementation is at the kernel level and involves controlling the order in which socket buffers are drained into the network. Experiments are executed both in a LAN and a WAN environment. We use the Linux operating system and the Apache and Flash web servers.Results indicate that SRPT-based scheduling of connections yields significant reductions in delay at the web server. These result in a substantial reduction in mean response time and mean slowdown for both the LAN and WAN environments. Significantly, and counter to intuition, the
requests for large files
are only negligibly penalized or not at all penalized as a result of SRPT-based scheduling.
Tutorial
Authors: Edwards Stephen A.
Published: May 2003

Embedded systems often include a traditional processor capable of executing sequential code, but both control and data-dominated tasks are often more naturally expressed using one of the many domain-specific concurrent specification languages. This article surveys a variety of techniques for translating these concurrent specifications into sequential code. The techniques address compiling a wide variety of languages, ranging from dataflow to Petri nets. Each uses a different method, to some degree chosen to match the semantics of concurrent language. Each technique is considered to consist of a partial evaluator operating on an interpreter. This combination provides a clearer picture of how parts of each technique could be used in a different setting.
Minimum delay optimization for domino logic circuits---a coupling-aware approach
Authors: Kim Ki-Wook , Jung Seong-Ook , Kim Taewhan , Kang Sung-Mo
Published: May 2003

Minimum delay associated with the hold time requirement is of concern to circuit designers, since race-through hazards are inherent in any multiple clock organization or clock distribution tree irrespective of clock frequency. The monotonic property of domino logic aggravates the min-delay path failure through coupling-induced speedup. To tackle the min-delay problem for domino logic, we propose a min-delay optimization algorithm considering coupling effects. Experimental results indicate that our algorithm yields a significant increase of min-delay without incurring max-delay violation.
Compacting sequences with invariant transition frequencies
Authors: Pinar Ali , Liu C. L.
Published: May 2003

Simulation-based power estimation is commonly used for its high accuracy despite excessive computation times. Techniques have been proposed to speed it up by compacting an input sequence while preserving its power-consumption characteristics. We propose a novel method to compact a sequence that preserves transition frequencies. We prove the problem is NP-complete, and propose a graph model to reduce it to that of finding a heaviest-weighted trail, and a heuristic utilizing this model. We also propose using multiple sequences for better accuracy with even shorter sequences. Experiments show that power dissipation can be estimated with an error of only 2.3%, while simulation times are reduced by 10. Proposed methods generate solutions that effectively preserve transition frequencies and that are very close to optimal. Experiments also show that multiple sequences grant more accurate results with even shorter sequences.
Sequential optimization in the absence of global reset
Authors: Singhal Vigyan , Pixley Carl , Aziz Adnan , Qadeer Shaz , Brayton Robert
Published: May 2003

We study the problem of optimizing synchronous sequential circuits. There have been previous efforts to optimize such circuits. However, all previous attempts make implicit or explicit assumptions about the design or the environment of the design. For example, it is widespread practice to assume the existence of a hardware reset line and consequently a fixed power-up state; in the absence of the same, a common premise is that the design's environment will apply an initializing sequence. We review the concept of
safe replaceability
which does away with these assumptions and the
delay-safe replaceability
notion, which is applicable when the design's output is not used for a certain number of cycles after power-up. We then develop procedures for optimizing the combinational next-state and output logic, as well as routines for reencoding the state space and removing state bits under these replaceability criteria. Experimental results demonstrate the effectiveness of our algorithms.
Compiler optimization on VLIW instruction scheduling for low power
Authors: Lee Chingren , Lee Jenq Kuen , Hwang Tingting , Tsai Shi-Chun
Published: May 2003

In this article, we investigate compiler transformation techniques regarding the problem of scheduling VLIW instructions aimed at reducing power consumption of VLIW architectures in the instruction bus. The problem can be categorized into two types: horizontal scheduling and vertical scheduling. For the case of horizontal scheduling, we propose a bipartite-matching scheme for instruction scheduling. We prove that our greedy bipartite-matching scheme always gives the optimal switching activities of the instruction bus for given VLIW instruction scheduling policies. For the case of vertical scheduling, we prove that the problem is NP-hard, and we further propose a heuristic algorithm to solve the problem. Our experiment is performed on Alpha-based VLIW architectures and an ATOM simulator, and the compiler incorporated in our proposed schemes is implemented based on SUIF and MachSUIF. Experimental results of horizontal scheduling optimization show an average 13.30% reduction with four-way issue architecture and an average 20.15% reduction with eight-way issue architecture for transitional activities of the instruction bus as compared with conventional list scheduling for an extensive set of benchmarks. The additional reduction for transitional activities of the instruction bus from horizontal to vertical scheduling with window size four is around 4.57 to 10.42%, and the average is 7.66%. Similarly, the additional reduction with window size eight is from 6.99 to 15.25%, and the average is 10.55%.
Performance issues and error analysis in an open-domain question answering system
Authors: Moldovan Dan , Paşca Marius , Harabagiu Sanda , Surdeanu Mihai
Published: May 2003

This paper presents an in-depth analysis of a state-of-the-art Question Answering system. Several scenarios are examined: (1) the performance of each module in a serial baseline system, (2) the impact of feedbacks and the insertion of a logic prover, and (3) the impact of various retrieval strategies and lexical resources. The main conclusion is that the overall performance depends on the depth of natural language processing resources and the tools used for answer finding.
A hierarchical access control model for video database systems
Authors: Bertino Elisa , Fan Jianping , Ferrari Elena , Hacid Mohand-Said , Elmagarmid Ahmed K. , Zhu Xingquan
Published: May 2003

Content-based video database access control is becoming very important, but it depends on the progresses of the following related research issues: (a) efficient video analysis for supporting semantic visual concept representation; (b) effective video database indexing structure; (c) the development of suitable video database models; and (d) the development of access control models tailored to the characteristics of video data. In this paper, we propose a novel approach to support multilevel access control in video databases. Our access control technique combines a video database indexing mechanism with a hierarchical organization of visual concepts (i.e., video database indexing units), so that different classes of users can access different video elements or even the same video element with different quality levels according to their permissions. These video elements, which, in our access control mechanism, are used for specifying the authorization objects, can be a semantic cluster, a subcluster, a video scene, a video shot, a video frame, or even a salient object (i.e., region of interest). In the paper, we first introduce our techniques for obtaining these multilevel video access units. We also propose a hierarchical video database indexing technique to support our multilevel video access control mechanism. Then, we present an innovative access control model which is able to support flexible multilevel access control to video elements. Moreover, the application of our multilevel video database modeling, representation, and indexing for MPEG-7 is discussed.
Some legal implications of the use of computers in the banking business
Authors: Freed Roy N.
Published: May 2003

The introduction of computers into the banking business has a wide variety of legal implications that merit careful attention at this very early stage. The industry is highly regulated by government and, hence, is subject to many statutes and regulations. It also is affected by important common law rules established by courts. The legal ramifications involve not only the mechanization itself, but also the very significant, economically attractive phenomenon of off premises processing. It is essential to identify and provide for many legal aspects right now, before systems and practices crystallize, in order to avoid the later impact of unanticipated physical complications and expense.The legal aspects of computerization in the banking business are especially diverse. In some states, there might be the basic question whether banks are authorized by law to invest in the new facilities, either directly or through cooperatives. More challenging are questions relating to off-premises processors, particularly with respect to the obligation not to disclose information concerning a bank's customers, the adequacy of fidelity bond coverage, the extent of liability for improper refusal to pay a check, and susceptibility to regulation by government agencies. Also pertinent is the propriety of data processing by banks for nonbank entities and particularly of the rendering of that service without charge for bank depositors.
A differential approach to inference in Bayesian networks
Authors: Darwiche Adnan
Published: May 2003

We present a new approach to inference in Bayesian networks, which is based on representing the network using a polynomial and then retrieving answers to probabilistic queries by evaluating and differentiating the polynomial. The network polynomial itself is exponential in size, but we show how it can be computed efficiently using an arithmetic circuit that can be evaluated and differentiated in time and space linear in the circuit size. The proposed framework for inference subsumes one of the most influential methods for inference in Bayesian networks, known as the tree-clustering or jointree method, which provides a deeper understanding of this classical method and lifts its desirable characteristics to a much more general setting. We discuss some theoretical and practical implications of this subsumption.
An analytic approach to the height of binary search trees II
Authors: Drmota Michael
Published: May 2003

It is shown that all centralized absolute moments
E
|

H
n

−
E

H
n

|
α
(α ≥ 0) of the height

H
n

of binary search trees of size
n
and of the saturation level

H
n

′ are bounded. The methods used rely on the analysis of a
retarded
differential equation of the form Φ′(
u
) = −α
−2
Φ(
u
/α)
2
with α > 1. The method can also be extended to prove the same result for the height of
m
-ary search trees. Finally the limiting behaviour of the distribution of the height of binary search trees is precisely determined.
Algorithms for computing the static single assignment form
Authors: Bilardi Gianfranco , Pingali Keshav
Published: May 2003

The Static Single Assignment (SSA) form is a program representation used in many optimizing compilers. The key step in converting a program to SSA form is called ϕ-placement. Many algorithms for ϕ-placement have been proposed in the literature, but the relationships between these algorithms are not well understood.In this article, we propose a framework within which we systematically derive (i) properties of the SSA form and (ii) ϕ-placement algorithms. This framework is based on a new relation called
merge
which captures succinctly the structure of a program's control flow graph that is relevant to its SSA form. The ϕ-placement algorithms we derive include most of the ones described in the literature, as well as several new ones. We also evaluate experimentally the performance of some of these algorithms on the SPEC92 benchmarks.Some of the algorithms described here are optimal for a single variable. However, their repeated application is not necessarily optimal for multiple variables. We conclude the article by describing such an optimal algorithm, based on the transitive reduction of the merge relation, for multi-variable ϕ-placement in structured programs. The problem for general programs remains open.
The use of web structure and content to identify subjectively interesting web usage patterns
Authors: Cooley Robert
Published: May 2003

The discipline of Web Usage Mining has grown rapidly in the past few years, despite the crash of the e-commerce boom of the late 1990s. Web Usage Mining is the application of data mining techniques to Web clickstream data in order to extract usage patterns. Yet, with all of the resources put into the problem, claims of success have been limited and are often tied to specific Web site properties that are not found in general. One reason for the limited success has been a component of Web Usage Mining that is often overlooked---the need to understand the content and structure of a Web site. The processing and quantification of a Web sites content and structure for all but completely static and single frame Web sites is arguably one of the most difficult tasks to automate in the Web Usage Mining process. This article shows that, not only is the Web Usage Mining process enhanced by content and structure, it cannot be completed without it. The results of experiments run on data from a large e-commerce site are presented to show that proper preprocessing cannot be completed without the use of Web site content and structure, and that the effectiveness of pattern analysis is greatly enhanced.
XDuce
Authors: Hosoya Haruo , Pierce Benjamin C.
Published: May 2003

XDuce is a statically typed programming language for XML processing. Its basic data values are XML documents, and its types (so-called
regular expression types
) directly correspond to document schemas. XDuce also provides a flexible form of
regular expression pattern matching
, integrating conditional branching, tag checking, and subtree extraction, as well as dynamic typechecking. We survey the principles of XDuce's design, develop examples illustrating its key features, describe its foundations in the theory of regular tree automata, and present a complete formal definition of its core, along with a proof of type safety.
Designing human-computer interfaces for quadriplegic people
Authors: Steriadis Constantine E. , Constantinou Philip
Published: May 2003

Computer and system manufacturers often say that designing applications for users with disabilities is not cost-effective. Most computer systems are designed for users who are not disabled; therefore, systems that address disabled users need special interfaces in order to be accessible. In this paper we present a method for developing human-computer interfaces for quadriplegic people in modern programming environments, provided that they can perform single-switch signals. Using a scanning technique, "single-switch" users can sequentially highlight items that are laid out spatially on screen and then select an item by activating a switch when the target item is highlighted.
Payments and banking with mobile personal devices
Authors: Herzberg Amir
Published: May 2003

Mobile devices enable secure, convenient authorization of e-banking, retail payment, brokerage, and other types of transactions.
Agility---
Authors: David Julie Smith , McCarthy William E. , Sommer Brian S.
Published: May 2003

The ideas of Darwinian evolution can illuminate the niches in which systems can flourish in today's tumultuous IT environment---and help identify the inevitable evolutionary changes.
"Of course it's true; I saw it on the Internet!"
Authors: Graham Leah , Metaxas Panagiotis Takis
Published: May 2003

Students use the Net as a primary source of information, usually with little or no regard as to the accuracy of that information.
IT outsourcing evolution---
Authors: Lee Jae-Nam , Huynh Minh Q. , Kwok Ron Chi-Wai , Pi Shih-Ming
Published: May 2003

To achieve complex solutions in the rapidly changing world of e-commerce, it is impossible to go it alone. This explains the latest trend in IT outsourcing---global and partner-based alliances. But where do we go from here?
In the zone
Authors: Armour Phillip
Published: May 2003

Blurring the lines of distinction between team roles is often necessary to adapt to a changing environment.
One giant step backward
Authors: Glass Robert L.
Published: May 2003

Old saying: "The more things change, the more they remain the same" …or do they?
Security problems in 802.11-based networks
Authors: Housley Russ , Arbaugh William
Published: May 2003

Assessing inherent wireless network security deficiencies and seeking solutions.
Security flaws in 802.11 data link protocols
Authors: Cam-Winget Nancy , Housley Russ , Wagner David , Walker Jesse
Published: May 2003

Understanding the difficulties in security protocol design and attempting to relocate the struggle between hacker and defender to a different protocol layer.
802.11b access point mapping
Authors: Byers Simon , Kormann Dave
Published: May 2003

Considering some of the practical issues encountered when finding and mapping wireless network access points.
Why Wi-Fi wants to be free
Authors: Schmidt Terry , Townsend Anthony
Published: May 2003

As the telecommunications industry wavers, a global grassroots movement is building the next-generation wireless network.
Seeds for random number generators
Authors: Marsaglia George
Published: May 2003

Techniques for choosing seeds for social and scientific applications of random number generators.
BrucellaStationary-Phase Gene Expression and Virulence
Authors: Roop II R. Martin , Gee Jason M. , Robertson Gregory T. , Richardson John M. , Ng Wai-Leung , Winkler Malcolm E.
Published: May 2003

▪ Abstract  The capacity of the Brucella spp. to establish and maintain long-term residence in the phagosomal compartment of host macrophages is critical to their ability to produce chronic infections in their mammalian hosts. The RNA binding protein host factor I (HF-I) encoded by the hfq gene is required for the efficient translation of the stationary-phase σ factor RpoS in many bacteria, and a Brucella abortus hfq mutant displays a phenotype in vitro, which suggests that it has a generalized defect in stationary-phase physiology. The inability of the B. abortus hfq mutant to survive and replicate in a wild-type manner in cultured murine macrophages, and the profound attenuation displayed by this strain and its B. melitensis counterpart in experimentally infected animals indicate that stationary-phase physiology plays an essential role in the capacity of the brucellae to establish and maintain long-term intracellular residence in host macrophages. The nature of the Brucella HF-I-regulated genes that have been identified to date suggests that the corresponding gene products contribute to the remarkable capacity of the brucellae to resist the harsh environmental conditions they encounter during their prolonged residence in the phagosomal compartment.
Nitrogen Assimilation and Global Regulation inEscherichia coli
Authors: Reitzer Larry
Published: May 2003

▪ Abstract  Nitrogen limitation in Escherichia coli controls the expression of about 100 genes of the nitrogen regulated (Ntr) response, including the ammonia-assimilating glutamine synthetase. Low intracellular glutamine controls the Ntr response through several regulators, whose activities are modulated by a variety of metabolites. Ntr proteins assimilate ammonia, scavenge nitrogen-containing compounds, and appear to integrate ammonia assimilation with other aspects of metabolism, such as polyamine metabolism and glutamate synthesis. The leucine-responsive regulatory protein (Lrp) controls the synthesis of glutamate synthase, which controls the Ntr response, presumably through its effect on intracellular glutamine. Some Ntr proteins inhibit the expression of some Lrp-activated genes. Guanosine tetraphosphate appears to control Lrp synthesis. In summary, a network of interacting global regulators that senses different aspects of metabolism integrates nitrogen assimilation with other metabolic processes.
How Bacteria Assemble Flagella
Authors: Macnab Robert M.
Published: May 2003

▪ Abstract  The bacterial flagellum is both a motor organelle and a protein export/assembly apparatus. It extends from the cytoplasm to the cell exterior. All the protein subunits of the external elements have to be exported. Export employs a type III pathway, also utilized for secretion of virulence factors. Six of the components of the export apparatus are integral membrane proteins and are believed to be located within the flagellar basal body. Three others are soluble: the ATPase that drives export, a regulator of the ATPase, and a general chaperone. Exported substrates diffuse down a narrow channel in the growing structure and assemble at the distal end, often with the help of a capping structure.
A Salvage Pathway for Protein Synthesis: tmRNA and Trans-Translation
Authors: Withey Jeffrey H. , Friedman David I.
Published: May 2003

▪ Abstract  Transfer-messenger RNA (tmRNA, or SsrA), found in all eubacteria, has both transfer and messenger RNA activity. Relieving ribosome stalling by a process called trans-translation, tmRNAala enters the ribosome and adds its aminoacylated alanine to the nascent polypeptide. The original mRNA is released and tmRNA becomes the template for translation of a 10-amino-acid tag that signals for proteolytic degradation. Although essential in a few bacterial species, tmRNA is nonessential in Escherichia coli and many other bacteria. Proteins known to be associated with tmRNA include SmpB, ribosomal protein S1, RNase R, and phosphoribosyl pyrophosphate. SmpB, having no other known function, is essential for tmRNA activity. trans-translation operates within ribosomes stalled both at the end of truncated mRNAs and at rare codons and some natural termination sites. Both the release of stalled ribosomes and the subsequent degradation of tagged proteins are important consequences of trans-translation.
CULTURAL ANDGENETICAPPROACHES TOMANAGINGMYCOTOXINS INMAIZE
Authors: Munkvold Gary P.
Published: May 2003

▪ Abstract  Infection of maize kernels by toxigenic fungi remains a challenging problem despite decades of research progress. Cultural practices, including crop rotation, tillage, planting date, and management of irrigation and fertilization, have limited effects on infection and subsequent mycotoxin accumulation. Current infrastructure and grain storage practices in developed countries can prevent postharvest development of mycotoxins, but this aspect remains a threat in developing countries, especially in tropical areas. Because most mycotoxin problems develop in the field, strategies are needed to prevent infection of growing plants by toxigenic fungi. Developing genetic resistance to Aspergillus flavus, Gibberella zeae, and Fusarium spp. (particularly F. verticillioides) in maize is a high priority. Sources of resistance to each of these pathogens have been identified and have been incorporated into public and private breeding programs. However, few, if any, commercial cultivars have adequate levels of resistance. Efforts to control infection or mycotoxin development through conventional breeding and genetic engineering are reviewed. The role of transgenic insect control in the prevention of mycotoxins in maize is discussed.
ECOLOGY OFMYCORRHIZAE: A Conceptual Framework for Complex Interactions Among Plants and Fungi
Authors: Allen M.F. , Swenson W. , Querejeta J.I. , Egerton-Warburton L.M. , Treseder K.K.
Published: May 2003

▪ Abstract  Mycorrhizae regulate elemental and energy flows in terrestrial ecosystems. We understand much of how mycorrhizae work, but integrating all possible mechanisms into a whole has proven elusive. Multiple evolutionary events and the long evolutionary history mean that different plants and fungi bring independent characteristics to the symbiosis. This variety results in extensive physiological variation. How do we integrate functional responses with diversity to understand the role of mycorrhizae in ecosystems? We review ecophysiological mechanisms of mycorrhizae and organize these into functional groups. Species-area relationships are not curvilinear, but resemble the “broken stick” model. We coupled functional groups with a metacommunity analysis to show how complex behavior can be generated using a simple matrix model of resource exchange. This approach provides insights into how we might integrate diversity and function across landscapes.