bluuebunny/crossref_metadata_2025 huggingface dataset:
DISTRIBUTED INFORMATION AND CONTROL IN A CONCURRENT HYPERMEDIA-ORIENTED ARCHITECTURE
Authors: DATTOLO ANTONINA , LOIA VINCENZO
Published: April 2003

The market for parallel and distributed computing systems keeps growing. Technological advances in processor power, networking, telecommunication and multimedia are stimulating the development of applications requiring parallel and distributed computing. An important research problem in this area is the need to find a robust bridge between the decentralisation of knowledge sources in information-based systems and the distribution of computational power. Consequently, the attention of the research community has been directed towards high-level, concurrent, distributed programming. This work proposes a new hypermedia framework based on the metaphor of the actor model. The storage and run-time layers are represented entirely as communities of independent actors that cooperate in order to accomplish common goals, such as version management or user adaptivity. These goals involve fundamental and complex hypermedia issues, which, thanks to the distribution of tasks, are treated in an efficient and simple way.
INTEGRATED SOFTWARE ENGINEERING AND KNOWLEDGE ENGINEERING TEACHING EXPERIENCES
Authors: DIESTE O. , JURISTO N. , MORENO A. M. , LOPEZ M.
Published: April 2003

This paper presents the motivations, experiences and results of teaching integrated Software Engineering (SE) and Knowledge Engineering (KE), specifically as part of the master course organized by the Polytechnic University of Madrid (School of Computer Science). The paper outlines a possible approach to this instruction, whose aim is for software practitioners thus educated to have a flexible and moldable view of the software systems development process. This broad and malleable approach allows future practitioners to better address the increasingly more complex, divergent and innovative problems and needs raised by users. This approach is the result of a gradual and continuous process. This paper discusses the current stage of integration, giving a detailed description and justification of the scope of the integrated instruction. For the purpose of quantitatively analyzing this experience, the paper also shows the results of the evaluation conducted throughout this process at three levels (industry, students and projects).
SUPPORTING DISTRIBUTED INDIVIDUAL TASKS IN COOPERATIVE SPECIFICATION DEVELOPMENT
Authors: SAEKI MOTOSHI , SUREERAT SAEEIAB , TANAKA AKIHIRO
Published: April 2003

This paper discusses a supporting tool for developing software specifications in collaboration of a team — for cooperative specification processes. Typical cooperative specification processes consist of three phases — (1) making a working plan by a team in face-to-face session, (2) performing an assigned task, i.e. designing an assigned part by each member in distributed session, and (3) integrating the developed products in face-to-face session. In this paper, we focus on the support for the second phase, i.e. performing the distributed individual task that a team leader has assigned in the first phase. Our supporting tool consists of two parts; one is called method base, a kind of CASE tool for individual use, and the other is a structured E-mail system for communication use. Method base has various catalogued specification and design methods, so a worker can select a suitable method for his problem domain. He can be navigated through the CASE tool, e.g. the diagram editor, that supports the selected method. Method base has information about product structures and the relationships among the product structures of the different methods. Thus method base can integrate the products developed with the multiple methods by different workers into one. The tools for communications among other members are necessary, and especially a kind of structured E-mail system is very useful for the members to communicate with each other in the second phase. Our E-mail system supports (1) sending and receiving the products with messages or with comments by using hyper-link mechanism, (2) composing comprehensive messages easily by using templates, (3) storing messages in structured mail folders and retrieving them, and (4) automatically notifying the modification of products and the progress status of development activities to the workers.
KNOWLEDGE ENGINEERING OF A MONITORING AND CONTROL DECISION SUPPORT SYSTEM
Authors: CHAN CHRISTINE WAICHI , KRITPIPHAT WEERAPONG , TONTIWACHWUTHIKUL PAITOON
Published: April 2003

This paper presents the Object-Oriented Knowledge Engineering (OOKE) methodology and its application in developing an expert system. OOKE is an expert system development methodology which incorporates the conceptual modelling tool of Inferential Modelling Technique into the analysis model of the Object-Oriented Software Engineering methodology. It was applied to develop a supervisory and decision support system for monitor and control of a water distribution system called the Water Advisor. The expertise, heuristics and reasoning knowledge of experts were acquired and then formulated in a model building process using the OOKE into a conceptual model which became the basis for a prototype expert system.
SPECIFYING SOFTWARE ARCHITECTURAL CONNECTORS IN SAM
Authors: HE XUDONG , DENG YI
Published: April 2003

Software architecture has become one of the most active research topics in software engineering in recent years. One of the distinct features of software architecture research is to explicitly study the interconnections (connectors) among system components. In this paper, we show how to formally specify several well-known general connectors in a software architecture methodology called SAM. Related work is discussed and compared. Our results establish the basis for reusing these defined connectors and for building more sophisticated connectors from them.
KNOWLEDGE ACQUISITION AND PROCESS GUIDANCE FOR BUILDING SYSTEM DYNAMICS SIMULATION MODELS: AN EXPERIENCE REPORT FROM SOFTWARE INDUSTRY
Authors: PFAHL DIETMAR , LEBSANFT KARL
Published: April 2003

System Dynamics (SD) is a method that allows for integrated modelling of technical as well as managerial aspects responsible for the dynamic complexity of systems. Therefore, simulation of SD models can also be a tool for problem analysis within software organisations.

In this paper, experience with SD modelling of software processes and projects within Siemens is reported. Special focus is put on problems encountered during knowledge acquisition for SD model building, like inadequate guidance while conducting SD modelling projects, and insufficient methodical support for re-using available or generating missing knowledge. Both problems were addressed in a research project, jointly conducted by Fraunhofer IESE and Siemens Corporate Technology. One of the results of this project is a prescriptive process model for building SD models. This process model, which is briefly outlined in the paper, provides guidance for a systematic development of SD models in software organisations.
OBJECT MODELING TO RE-ENGINEER LEGACY SYSTEMS
Authors: GUO JIANG , LUQI
Published: April 2003

This paper summarizes our experiences in using computer-supported methods to develop a software architecture to support the re-engineering of the Janus Combat Simulation System. We have analyzed the Janus FORTRAN source code, interviewed Janus domain experts, developed an object-oriented architecture for the Janus Combat Simulation subsystem, and validated the architecture with an executable prototype. In this paper, we propose methods to facilitate the evolution of the software component of these systems by recovering the behavior of the systems using systematic methods, and illustrate their use in the context of the Janus System.
USING INCREMENTAL PLANNING TO FOSTER APPLICATION FRAMEWORK REUSE
Authors: ORTIGOSA ALVARO , CAMPO MARCELO
Published: April 2003

In this work, we present an approach for documenting object-oriented application frameworks and use the documentation to guide the framework instantiation process. Our approach is based on a shift from a framework-centered to a functionality-centered documentation, through which a tool can guide the instantiation process according to the functionality required for the new application. The fundamental idea of our work is the combination of the concept of user-tasks modeling and least commitment planning methods to guide the instantiation process. Based on these techniques, the tool is able to present the different high level activities that can be carried out when creating a new application from a framework to the developer, taking as a basis the documentation provided by the designer through instantiation rules.
UML AS DOMAIN SPECIFIC LANGUAGE FOR THE CONSTRUCTION OF KNOWLEDGE-BASED CONFIGURATION SYSTEMS
Authors: FELFERNIG ALEXANDER , FRIEDRICH GERHARD E. , JANNACH DIETMAR
Published: April 2003

In many domains, software development has to meet the challenges of developing highly adaptable software very rapidly. In order to accomplish this task, domain specific, formal description languages and knowledge-based systems are employed. From the viewpoint of the industrial software development process, it is important to integrate the construction and maintenance of these systems into standard software engineering processes. In addition, the descriptions should be comprehensible for the domain experts in order to facilitate the review process.

For the realization of product configuration systems, we show how these requirements can be met by using a standard design language (UML-Unified Modeling Language) as notation in order to simplify the construction of a logic-based description of the domain knowledge. We show how classical description concepts for expressing configuration knowledge can be introduced into UML and be translated into logical sentences automatically. These sentences are exploited by a general inference engine solving the configuration task.
FORMAL SPECIFICATION AND PROTOTYPING OF MULTIMEDIA APPLICATIONS
Authors: ARNDT TIMOTHY , CHANG SHI-KUO , GUERCIO ANGELA
Published: April 2003

Multimedia systems incorporating hyperlinks and user interaction can be prototyped using TAOML, an extension of HTML. TAOML is used to define a Teleaction Object (TAO) which is a multimedia object with associated hypergraph structure and knowledge structure The hypergraph structure supports the effective presentation and efficient communication of multimedia information. In this paper, a formal specification methodology for TAOs using Symbol Relation (SR) grammars is described. An attributed SR grammar is then introduced in order to associate knowledge with the TAO. The limitations to achieve an efficient parser are given. The grammatical formalism allows for validation and verification of the system specification. This methodology provides a principled approach to specify, verify, validate and prototype multimedia applications.
ISSUES WITH META-KNOWLEDGE
Authors: MENZIES TIM , ALTHOFF KLAUS-DIETER , KALFOGLOU YANNIS , MOTTA ENRICO
Published: April 2003

At the SEKE'99 conference, knowledge engineering researchers held a panel on the merits of meta-knowledge (i.e. problem solving methods and ontologies) for the development of knowledge-based systems. The original panel was framed as a debate on the merits of meta-knowledge for knowledge maintenance [21]. However, the debate quickly expanded. In the end, we were really discussing the merits of different technologies for the specification of reusable components for KBS. In this brief article we record some of the lively debate from that panel and the email exchanges it generated.
ISSUES AND MODELS IN SOFTWARE PRODUCT LINES
Authors: DIAZ-HERRERA JORGE L. , KNAUBER PETER , SUCCI GIANCARLO
Published: April 2003

Software product lines are one of the most promising fields in software engineering. They aim at the synergistic construction of software products. A successful introduction of software product lines requires three essential ingredients: a business analysis of the overall advantages that can come from product lines, the definition of a systematic process for product lines development, and the definition of general models, in a standard format, which can guide the development process.
DISTRIBUTED PROCESS PLANNING SUPPORT WITH MILOS
Authors: GOLDMANN SIGRID , MÜNCH JÜRGEN , HOLZ HARALD
Published: April 2003

Software development processes are highly creative, and therefore prone to change frequently. Also, recent developments show that most software projects require knowledge and skills in a lot of areas. Since the necessary expertise often cannot be found at one development site, the necessity arises to distribute projects among several sites, or form "virtual" corporations, where software development is shared between several companies. The first point makes it necessary to support changes by identifying and notifying the people affected by a change. The second point emphasizes this necessity, while also complicating project planning and management: changes in one development site or company might necessitate replanning in several locations. In this paper, we introduce the MILOS approach, which provides concepts to integrate process modeling, planning, scheduling and enactment in one system. Thus dynamic plan changes, as well as automated feedback from execution to the project plan can be supported.
A METRIC FOR THE SIZE ESTIMATION OF OBJECT-ORIENTED GRAPHICAL USER INTERFACES
Authors: COSTAGLIOLA G. , FERRUCCI F. , TORTORA G. , VITIELLO G.
Published: April 2003

In order to achieve quality products with reliable cost and effort estimations, one of the main tasks for planning software project development is size estimation. This is especially true when dealing with interactive applications which represent critical components in a software project. In the paper, we address the problem of the size estimation of interactive graphical applications developed using the object-oriented methodology. In particular, we define and validate a metric, the Class Point metric, for estimating the size of object-oriented GUIs. The method is based on the idea of quantifying classes in a program analogous to function counting performed by the function point metric. Theoretical validation has proven the consistency of the Class Point metric as size measure. Empirical validation provides evidence that the Class Point metric is a useful measure for OO software size.
A DESIGN RATIONALE BASED ENVIRONMENT FOR COOPERATIVE MAINTENANCE
Authors: CANFORA GERARDO , CASAZZA GERARDO , DE LUCIA ANDREA
Published: April 2003

This paper describes Cooperative Maintenance Conceptual Model ( CM 2), a conceptual model aimed at supporting software maintenance in a collaborative fashion. The main goal of CM 2 is to support the software maintenance process through the acquisition, structuring and distribution of the information concerned with the maintenance process itself. Information is structured as a network of linked comments and concerns both the analysis and design activities (Rationale in the Large) and the implementation of a change (Rationale in the Small). We also present COMANCHE (COoperative MAintenance Network Centered Hypertextual Enviroment), an enviroment which reflects the CM 2 ideas and principles.
PRODUCTION AND MAINTENANCE OF GOAL-ORIENTED SOFTWARE MEASUREMENT MODELS
Authors: CANTONE GIOVANNI , DONZELLI PAOLO
Published: April 2003

Production and maintenance of measurement models are crucial in the context of an advanced software development organization.

The paper suggests a goal-oriented measurement model life cycle that, starting out from the high-level organizational goals, drives software organizations towards a structured process to deal with measurement models. The life cycle results into an integrated component of the management activities pointed to generate, refine, and fulfill the organizational goals, whereas the final measurement models become items of a purpose fitting measurement plan.

For each phase of the life cycle, the main activities, with their inputs and outputs, are identified and, moreover, some driving templates are defined. The paper analyzes their interactions with the other software production and management-related tasks and proposes a possible allocation within an Experience Factory-based software organization.
MULTIPLE VIEWS ANALYSIS OF SOFTWARE DESIGNS
Authors: BELKHOUCHE BOUMEDIENE , LEMUS–OLALDE CUAUHTÉMOC
Published: April 2003

Designs are expressed in terms of structure, behavior, objects, modules, and functions which, once consolidated, become design blueprints. This paper describes a formal framework for expressing, analyzing, and comparing multiple views of designs. The analysis of multiple designs or views using different design notations is proposed as a strategy to enhance design quality by providing a systematic identification of design defects and discrepancies. Views are formalized, analyzed independently, and then compared to each other. The type of design discrepancies identified are omission of information, incompatible information, and inconsistencies between views.
MULTI-PERSPECTIVE SPECIFICATION, DESIGN AND IMPLEMENTATION OF SOFTWARE COMPONENTS USING ASPECTS
Authors: GRUNDY JOHN
Published: April 2003

Current approaches to component-based systems engineering tend to focus on low-level software component interface design and implementation. This often leads to the development of components whose services are hard to understand and combine, make too many assumptions about other components they can be composed with and component documentation that is too low-level. Aspect-oriented component engineering is a new methodology that uses a concept of different system capabilities ("aspects") to categorise and reason about inter-component provided and required services. It supports the identification, description and reasoning about high-level component functional and non-functional requirements grouped by different systemic aspects, and the refinement of these requirements into design-level software component service implementation aspects. Aspect information is used to help implement better component interfaces and to encode knowledge of a component's capabilities for other components, developers and end users to access. We describe and illustrate the use of aspect-oriented component engineering techniques and notations to specify, design and implement software components, report on some basic tool support, and our experiences using the approach to build some complex, component-based software systems.
AN INTEGRATED CLASSIFICATION-TREE METHODOLOGY FOR TEST CASE GENERATION
Authors: CHEN T. Y. , POON P. L. , TSE T. H.
Published: April 2003

This paper describes an integrated methodology for the construction of test cases from functional specifications using the classification-tree method. It is an integration of our extensions to the classification-hierarchy table, the classification tree construction algorithm, and the classification tree restructuring technique. Based on the methodology, a prototype system ADDICT, which stands for AutomateD test Data generation system using the Integrated Classification-Tree method, has been built.
PERFORMANCE ANALYSIS OF TRAFFIC CONTROL SYSTEMS BASED UPON STOCHASTIC TIMED PETRI NET MODELS
Authors: WANG JIACUN , DENG YI , JIN CHUN
Published: April 2003

A compositional modeling and performance evaluation technique for traffic control systems based on Stochastic Timed Petri Nets (STPN's) is presented. We use STPN's to specify traffic and traffic control at an intersection and use a random distribution model to model the motion of vehicles in a road segment between any two consecutive intersections. A traffic control system is thus modeled as a composition of individual intersection models and segment random distribution models. A technique is presented to incrementally evaluate the system's performance by analyzing intersections separately according to a carefully selected order. The analysis technique conforms to the accepted practice of transportation research. Compared to existing Petri net models of traffic control systems, our technique dramatically reduces the complexity of analysis.
AN INFRASTRUCTURE FOR ENGINEERING COOPERATIVE AGENTS
Authors: YUAN SOE-TSYR , WU ZENG-LUNG
Published: April 2003

Currently, systems of cooperative agents (multi-agent systems), possessing the capabilities of autonomy, adaptation, and cooperation, are being used in an increasingly wide variety of application areas, and the conversation-based multi-agent system design is the major design for those multi-agent systems. Supposedly, conversation-based multi-agent systems should have been prevailing enough for tackling dynamic aspects of problems in a variety of domains. However, for industries, multi-agent systems are still found to be in the birth stage where they only show their new values in anticipation for further explorations and improvements in order to attract critical mass of users of information executives or software developers. Nevertheless, what are the success factors that can result in a critical mass of multi-agent system designers? This paper shows one possible success factor — an infrastructure for the bottom-up design of multi-agent systems. The bottom-up design makes it possible for agents to be reassembled into multi-agent systems and reused as needed. However, what do we need to successfully support the bottom-up design? This paper is the first attempt to present a tool that fully supports the bottom-up design of multi-agent systems. The tool has three parts. The first part is a wrapper that wraps each agent so that it exempts the designers from the careful detailed deployment of the inter-relationships between cooperation knowledge and task knowledge inside the agent. This wrapper should be independent of the functions of agents. The second part is an environment that can support the wrapper to automate the cooperation process on behalf of agents. The third part is a graphical assembly panel for developers to visually configure wrapped agents residing at different places of the Internet into a working multi-agent system.
COMPONENT-BASED VERIFICATION IN A SYNCHRONOUS SETTING
Authors: MERCERON AGATHE , PINNA G. MICHELE
Published: April 2003

Formal verification of properties in reactive real-time systems is crucial, as these systems are often safety-critical. Such systems are successfully implemented using synchronous languages, where refinement is a relevant operation. This paper investigates the interplay between this operation and formal verification. It turns out that, while for the refined program component-based verification of properties expressed using suitable temporal logics is easily achieved, component-based verification from the point of view of the refining program is best achieved with observers. Our results are based on a translation of synchronous programs into Boolean automata. Their practical relevance is illustrated with a protocol case study.
A STUDY ON A PATH-BASED STRATEGY FOR SELECTING BLACK-BOX GENERATED TEST CASES
Authors: YU Y. T. , TANG S. F. , POON P. L. , CHEN T. Y.
Published: April 2003

Various black-box methods for the generation of test cases have been proposed in the literature. Many of these methods, including the category-partition method and the classification-tree method, follow the approach of partition testing, in which the input domain is partitioned into subdomains according to important aspects of the specification, and test cases are then derived from the subdomains. Though comprehensive in terms of these important aspects, execution of all the test cases so generated may not be feasible under the constraint of tight testing resources. In such circumstances, there is a need to select a smaller subset of test cases from the original test suite for execution. In this paper, we propose the use of white-box information to guide the selection of test cases from the original test suite generated by a black-box testing method. Furthermore, we have developed some techniques and algorithms to facilitate the implementation of our approach, and demonstrated its viability and benefits by means of a case study.
A CONSTRAINT SOLVER AND ITS APPLICATION TO PATH FEASIBILITY ANALYSIS
Authors: ZHANG JIAN , WANG XIAOXU
Published: April 2003

Many testing methods are based on program paths. A well-known problem with them is that some paths are infeasible. To decide the feasibility of paths, we may solve a set of constraints. In this paper, we describe constraint-based tools that can be used for this purpose. They accept constraints expressed in a natural form, which may involve variables of different types such as integers, Booleans, reals and fixed-size arrays. The constraint solver is an extension of a Boolean satisfiability checker and it makes use of a linear programming package. The solving algorithm is described, and examples are given to illustrate the use of the tools. For many paths in the testing literature, their feasibility can be decided in a reasonable amount of time.
AN OBJECT-BASED DATA FLOW TESTING APPROACH FOR WEB APPLICATIONS
Authors: LIU CHIEN-HUNG , KUNG DAVID C. , HSIA PEI , HSU CHIH-TUNG
Published: April 2003

In recent years, Web applications have grown rapidly because of their abilities to provide online information access to anyone at anytime around the world. As Web applications become complex, there is a growing concern about their quality and reliability. This paper extends traditional data flow testing techniques to Web applications. Several data flow issues about analyzing HyperText Markup Language (HTML) documents in Web applications are discussed. An object-based data flow testing approach is presented. The approach is based on a test model that captures data flow test artifacts of Web applications. In the test model, each entity of a Web application is modeled as an object. The data flow information of the functions within an object or across objects is then captured using various flow graphs. Based on the object-based test model, data flow test cases for a Web application can be systematically and selectively generated in five different levels.
THE PROPERTY FDT IS UNDECIDABLE FOR FINITELY PRESENTED MONOIDS THAT HAVE POLYNOMIAL-TIME DECIDABLE WORD PROBLEMS
Authors: OTTO F. , SATTLER-KLEIN A.
Published: April 2003

By exploiting a new technique for proving undecidability results developed by A. Sattler-Klein in her doctoral dissertation (1996) it is shown that it is undecidable in general whether or not a finitely presented monoid with a polynomial-time decidable word problem has finite derivation type (FDT). This improves upon the undecidability result of R. Cremanns and F. Otto (1996), which was based on the undecidability of the word problem for the finitely presented monoids considered.
TRIANGULAR MONOIDS AND AN ANALOG TO THE DERIVED SEQUENCE OF A SOLVABLE GROUP
Authors: BAUER CRAIG
Published: April 2003

A sequence is defined for a monoid consisting of upper triangular matrices. This sequence is analogous to the derived sequence of the solvable group. The relationship between the two sequences is investigated and sets of upper triangular partial permutation matrices, which arise naturally from this relation, are examined.
COUNTING FINITE ALGEBRAS IN THE POST VARIETIES
Authors: BERMAN JOEL , IDZIAK PAWEŁ
Published: April 2003

The G -spectrum of a class of algebras is the function that counts, up to isomorphism, the number of at most k -generated algebras in the class, for k =1,2,… . We consider the G -spectra of the varieties of algebras generated by a single two-element algebra. We show that such spectra are either polynomial, exponential, or at least doubly exponential as a function of k . For the varieties that have polynomial or exponential G -spectra we provide an exact formula for the function.
FREE GROUP ROOTS OF akbl AND [ ak,b]
Authors: McCOOL JAMES
Published: April 2003

Let F be a free group with basis a, b, …, and let u, w ∈ F . We say that u is a root of w if w belongs to the normal closure of u in F . We show that if w is of the form akbl then w has only a finite number of conjugacy classes of roots, and that given k and l the set of roots of w can be algorithmically determined. We also classify the roots of elements of the form akba-kb-1.
THE POWER OF THE GROUP-IDENTITIES FOR ITERATION
Authors: ÉSIK Z.
Published: April 2003

It has been shown that the axioms of iteration theories capture the equational properties of iteration in several different models related to computer science. Iteration theories are axiomatizable by the Conway identities and the group-identities corresponding to the finite (simple) groups. In this paper we provide a complete analysis of these identities by giving a concrete description of the free theories in the variety axiomatized by the Conway identities and any given subcollection of the group-identities. It follows that when the group-identities are effectively given, the equational theory of the variety is decidable.
ENUMERATION OF CAT1-GROUPS OF LOW ORDER
Authors: ALP MURAT , WENSLEY CHRISTOPHER D.
Published: April 2003

In this paper we describe a share package [Formula: see text] of functions for computing with finite, permutation crossed modules, cat1-groups and their morphisms, written using the [Formula: see text] group theory programming language. The category XMod of crossed modules is equivalent to the category Cat1 of cat1-groups and we include functions emulating the functors between these categories. The monoid of derivations of a crossed module [Formula: see text] , and the corresponding monoid of sections of a cat1-group [Formula: see text] , are constructed using the Whitehead multiplication. The Whitehead group of invertible derivations, together with the group of automorphisms of [Formula: see text] , are used to construct the actor crossed module of [Formula: see text] which is the automorphism object in XMod. We include a table of the 350 isomorphism classes of cat1-structures on groups of order at most 30.
THE LATTICE OF PERMUTATIONS IS BOUNDED
Authors: CASPARD NATHALIE
Published: April 2003

The purpose of this paper is to show that the lattice [Formula: see text] of permutations on a n -element set is bounded. This result strengthens the semi-distributive nature of the lattice [Formula: see text]. To prove this property, we use a characterization of the class of bounded lattices in terms of arrows relations defined on the join-irreducible elements of a lattice or, more precisely, in terms of the A-table of a lattice.
FREE PROFINITE SEMIGROUPS OVER SOME CLASSES OF SEMIGROUPS LOCALLY IN ${\mathcal D} {\rm G}$
Authors: CARLOS COSTA JOSÉ
Published: April 2003

This paper is concerned with the structure of semigroups of implicit operations on various subpseudovarieties V of [Formula: see text] ∩ [Formula: see text], where [Formula: see text] and [Formula: see text] are the pseudovarieties of all semigroups S in which each regular [Formula: see text] -class is, respectively, a rectangular group and a group, and where [Formula: see text] is the pseudovariety of semigroups locally in [Formula: see text] As an application, we give a characterization of the variety of languages recognized by semigroups in V and derive some join decompositions of pseudovarieties.
FINITELY BASED WORDS
Authors: SAPIR OLGA
Published: April 2003

Let W be a finite language and let Wc be the closure of W under taking subwords. Let S(W) denote the Rees quotient of a free monoid over the ideal consisting of all words that are not in Wc. We call W finitely based if the monoid S(W) is finitely based. Although these semigroups have easy structure they behave "generically" with respect to the finite basis property [6]. In this paper, we describe all finitely based words in a two-letter alphabet. We also find some necessary and some sufficient conditions for a set of words to be finitely based.
FINITE SUBGROUPS OF HYPERBOLIC GROUPS
Authors: BRADY NOEL
Published: April 2003

We prove that every finite subgroup of a hyperbolic group G can be conjugated to a 2δ+1 neighborhood of the identity element, where δ is the hyperbolicity constant for G with respect to a given generating set. This gives an upper bound for the size of such finite subgroups in terms of δ and the number of generators for G.
FINITE AUTOMATA OVER FREE GROUPS
Authors: DASSOW JÜRGEN , MITRANA VICTOR
Published: April 2003

Finite automata are extended by adding an element of a given group to each of their configurations. An input string is accepted if and only if the neutral element of the group is associated to a final configuration reached by the automaton. We get a new characterization of the context-free languages as soon as the considered group is the binary free group. The result cannot be carried out in the deterministic case. Some remarks about finite automata over other groups are also presented.
FINITELY BASED, FINITE SETS OF WORDS
Authors: JACKSON MARCEL , SAPIR OLGA
Published: April 2003

For W a finite set of words, we consider the Rees quotient of a free monoid with respect to the ideal consisting of all words that are not subwords of W. This resulting monoid is denoted by S(W). It is shown that for every finite set of words W, there are sets of words U⊃W and V⊃W such that the identities satisfied by S(V) are finitely based and those of S(U) are not finitely based [regardless of the situation for S(W)]. The first examples of finitely based (not finitely based) aperiodic finite semigroups whose direct product is not finitely based (finitely based) are presented and it is shown that every monoid of the form S(W) with fewer than 9 elements is finitely based and that there is precisely one not finitely based 9 element example.
ON THE SOLUTION OF CERTAIN EQUATIONS WITH EXPONENT SUM 0 OVER Z2
Authors: FERLINI V. , GOLDSTEIN R. , SALPUKAS M.
Published: April 2003

Let G be a finite group. A Corollary of a result of Gerstenhaber and Rothaus [3] states that all equations in one variable over G with exponent sum nonzero are solvable over G. Lyndon [6] studied equations in one variable with exponent sum zero over Zm. He showed that there was a relatively simple equation with no solution over Z2. In this paper we will initiate a study of equations with exponent sum zero over Z2. In particular we will show whether or not certain equations, which are generalizations of the equation studied by Lyndon, have solutions over Z2. We are grateful to the referee whose suggestion for the case when p<0<q both simplified and generalized our original result. This paper constitutes part of the theses of the first and third named authors.
FREE TERNARY ALGEBRAS
Authors: BALBES RAYMOND
Published: April 2003

A ternary algebra is a bounded distributive lattice with additonal operations e and ~ that satisfies (a+b)~=a~b~, a~~=a, e≤a+a~, e~= e and 0~=1. This article characterizes free ternary algebras by giving necessary and sufficient conditions on a set X of free generators of a ternary algebra L, so that X freely generates L. With this characterization, the free ternary algebra on one free generator is displayed. The poset of join irreducibles of finitely generated free ternary algebras is characterized. The uniqueness of the set of free generators and their pseudocomplements is also established.
POLYNOMIAL INDEX GROWTH GROUPS
Authors: BALOG ANTAL , PYBER LÁSZLÓ , MANN AVINOAM
Published: April 2003

We show that the order of a finite simple of Lie type is bounded by a small constant power of its exponent. This confirms, in a strengthened form, a conjecture of Vaughan-Lee and Zel'manov on the order and exponent of almost simple groups.

We also obtain various structural restrictions on groups of polynomial index growth.

Combining the above results we construct finitely generated residually finite groups of polynomial index growth which are neither linear nor boundedly generated. This answers questions of Segal and Platonov–Rapinchuk respectively. A further question of Platonov–Rapinchuk concerning a weakened polynomial index growth assumption is also answered.
GENERALIZED POST CORRESPONDENCE PROBLEM FOR MARKED MORPHISMS
Authors: HALAVA VESA , HARJU TERO , HIRVENSALO MIKA
Published: April 2003

We prove that the generalized Post Correspondence Problem (GPCP) is decidable for marked morphisms. This result gives as a corollary a shorter proof for the decidability of the binary PCP, proved in 1982 by Ehrenfeucht, Karhumäki and Rozenberg.
THE TITS CONJECTURE FOR LOCALLY REDUCIBLE ARTIN GROUPS
Authors: CHARNEY RUTH
Published: April 2003

Given an Artin system (A,S), a conjecture of Tits states that the subgroup A(2) of A generated by the squares of the generators in S is subject only to the obvious commutator relations between generators. In particular, A(2) is a right-angled Artin group. We prove this conjecture for a class of infinite type Artin groups, called locally reducible Artin groups, for which the associated Deligne complex has a CAT(0) geometry. We also prove that for any special subgroup AT of A, A(2)∩AT=(AT)(2).
APPROXIMATION AND COMPARISON FOR NONSMOOTH ANISOTROPIC MOTION BY MEAN CURVATURE IN ℝN
Authors: BELLETTINI G. , NOVAGA M.
Published: April 2003

We prove that a reaction-diffusion inclusion provides a sub-optimal approximation for anisotropic motion by mean curvature in the nonsmooth case. This result is valid in any space dimension and with a time-dependent driving force, provided we assume the existence of a regular flow. The crystalline case is included. As a by-product of our analysis, a comparison theorem between regular flows is obtained. This result implies uniqueness of the original flow.
NUMERICAL ANALYSIS OF ITERATIVE ALGORITHMS FOR AN INVERSE BOUNDARY TRANSPORT PROBLEM
Authors: AGOSHKOV V. I. , PARMUZIN E. I. , SHUTYAEV V. P. , BARDOS C.
Published: April 2003

The paper deals with numerical analysis of an inverse boundary transport problem. A class of iterative algorithms for solving this problem is considered, the algorithms convergence conditions are studied, and the convergence rate estimates are derived. Numerical examples are presented.
ERROR GROWTH AND A POSTERIORI ERROR ESTIMATES FOR CONSERVATIVE GALERKIN APPROXIMATIONS OF PERIODIC ORBITS IN HAMILTONIAN SYSTEMS
Authors: LARSON MATS G.
Published: April 2003

We prove an a posteriori error estimate for approximations of periodic orbits in Hamiltonian systems using Galerkin methods which conserve the Hamiltonian. The error is estimated in terms of the local time step, the residual obtained by inserting the approximate solution into the differential equation, and a stability factor describing relevant stability properties of the adjoint linearized problem. The quantitative growth of the stability factor as a function of time is of particular interest. We show that the stability factor grows linearly with time for a certain class of problems when the conservative scheme is used, in contrast to the quadratic growth of the stability factor, expected for non-conservative schemes in general.
REITERATED HOMOGENIZATION OF INTEGRAL FUNCTIONALS
Authors: BRAIDES ANDREA , LUKKASSEN DAG
Published: April 2003

We consider the homogenization of sequences of integral functionals defined on media with several length-scales. Our general results connected to the corresponding homogenized functional are used to analyze new types of structures and to illustrate the wide range of effective properties achievable through reiteration. In particular, we consider a two-phase structure which is optimal when the integrand is a quadratic form and point out examples where the macroscopic behavior of this structure underlines an effective energy density which is lower than that of the best possible multirank laminate. We also present some results connected to a reiterated structure where the effective property is extremely sensitive of the growth of the integrand.
SIMULATION AND MODELLING OF FLOWS BETWEEN ROTATING CYLINDERS.
Authors: DE SOCIO L. M. , MARINO L.
Published: April 2003

The equations which govern a number of models for flows between rotating cylinders at different Knudsen numbers are solved numerically by means of the direct simulation Monte Carlo method (DSMCM) to show their limitations. The DSMC code was firstly tested and validated against existing experimental data and then its results represented the reference data base for evaluating the characteristics of each model.
WEAK APPROXIMATION OF THE ψ–ω EQUATIONS WITH EXPLICIT VISCOUS DIFFUSION
Authors: GUERMOND J.-L. , QUARTAPELLE L.
Published: April 2003

This paper describes a variational formulation for solving the 2-D time-dependent incompressible Navier–Stokes equations expressed in the stream function and vorticity. The difference between the proposed approach and the standard one is that the vorticity equation is interpreted as an evolution equation for the stream function while the Poisson equation is used as an expression for evaluating the distribution of vorticity in the domain and on the boundary. A time discretization is adopted with the viscous diffusion made explicit, which leads to split the incompressibility from the viscosity. In some sense, the present method generalizes to the variational framework a well-known idea which is used in finite differences approximations and that is based on a Taylor series expansion of the stream function near the boundary. Some conditional stability results and error estimates are given.
ENTROPY SOLUTIONS IN THE STUDY OF ANTIPLANE SHEAR DEFORMATIONS FOR ELASTIC SOLIDS
Authors: ANDREU FUENSANTA , MAZÓN JOSÉ M. , SOFONEA MIRCEA
Published: April 2003

The concept of entropy solution was recently introduced in the study of Dirichlet problems for elliptic equations and extended for parabolic equations with nonlinear boundary conditions. The aim of this paper is to use the method of entropy solutions in the study of a new problem which arise in the theory of elasticity. More precisely, we consider here the infinitesimal antiplane shear deformation of a cylindrical elastic body subjected to given forces and in a frictional contact with a rigid foundation. The elastic constitutive law is physically nonlinear and the friction is described by a static law. We present a variational formulation of the model and prove the existence and the uniqueness of a weak solution in the case when the body forces and the prescribed surface tractions have the regularity L∞. The proof is based on classical results for elliptic variational inequalities and measure theory arguments. We also define the concept of entropy solution and we prove an existence and uniqueness result in the case when the body forces and the surface tractions have the regularity L1. The proof is based on properties of the trace operators for functions which are not in Sobolev spaces. Finally, we present a regularity result for the entropy solution and we give some concrete examples and mechanical interpretation.
BOUNDARY CONDITIONS AND EXISTENCE RESULTS FOR LEVERMORE'S MOMENTS SYSTEM
Authors: LE TALLEC P. , PERLAT J. P.
Published: April 2003

This paper considers the 14 moment expansion of the Boltzmann equation proposed by D. Levermore. After a brief review of this model, we derive weak boundary conditions compatible with the hyperbolic structure of the model, and express in average the microscopic boundary conditions imposed to the gas. This choice of half flux boundary conditions is justified by a mathematical analysis of the resulting linearized problem. Using standard parabolic regularization arguments and a specific dissipation inequality, we prove that the linearized problem has a unique solution.
DECREASE OF THE FISHER INFORMATION FOR SOLUTIONS OF THE SPATIALLY HOMOGENEOUS LANDAU EQUATION WITH MAXWELLIAN MOLECULES
Authors: VILLANI C.
Published: April 2003

We give a direct proof of the fact that, in any dimension of the velocity space, Fisher's quantity of information is nonincreasing with time along solutions of the spatially homogeneous Landau equation for Maxwellian molecules. This property, which was first seen in numerical simulation in plasma physics, is linked with the theory of the spatially homogeneous Boltzmann equation.
MATHEMATICAL PROPERTIES OF INELASTIC SCATTERING MODELS IN LINEAR KINETIC THEORY
Authors: BANASIAK JACEK
Published: April 2003

In this paper we analyse properties of collision operators which occur in linear Boltzmann–Maxwell models with inelastic scattering. In particular, we prove the solvability of the Cauchy problem for such models. These results form a basis for further applications of these models and, in particular, for their asymptotic analysis and the derivation of the drift–diffusion approximation.
BLOOD FLOW THROUGH A CIRCULAR PIPE WITH AN IMPULSIVE PRESSURE GRADIENT
Authors: PONTRELLI GIUSEPPE
Published: April 2003

The unsteady flow of a viscoelastic fluid in a straight, long, rigid pipe, driven by a suddenly imposed pressure gradient is studied. The used model is the Oldroyd-B fluid modified with the use of a nonconstant viscosity, which includes the effect of the shear-thinning of many fluids. The main application considered is in blood flow.

Two coupled nonlinear equations are solved by a spectral collocation method in space and the implicit trapezoidal finite difference method in time. The presented results show the role of the non-Newtonian terms in unsteady phenomena.
ON THE REPRESENTATION OF ENERGY AND MOMENTUM IN ELASTICITY
Authors: PODIO-GUIDUGLI P. , SELLERS S. , VERGARA CAFFARELLI G.
Published: April 2003

In order to clarify common assumptions on the form of energy and momentum in elasticity, a generalized conservation format is proposed for finite elasticity, in which total energy and momentum are not specified a priori. Velocity, stress, and total energy are assumed to depend constitutively on deformation gradient and momentum in a manner restricted by a dissipation principle and certain mild invariance requirements. Under these assumptions, representations are obtained for energy and momentum, demonstrating that (i) the total energy splits into separate internal and kinetic contributions, and (ii) the momentum is linear in the velocity. It is further shown that, if the stress response is strongly elliptic, the classical specifications for kinetic energy and momentum are sufficient to give elasticity the standard format of a quasilinear hyperbolic system.
DISSIPATIVITY AND IRREVERSIBILITY OF ELECTROMAGNETIC SYSTEMS
Authors: FABRIZIO MAURO , MORRO ANGELO
Published: April 2003

A new approach is developed for the thermodynamics of electromagnetic materials with memory by viewing them as dynamical systems. Though results are also derived for nonlinear materials with instantaneous response, an exhaustive set of thermodynamic restrictions is derived for the case where the response is determined by linear functionals of the histories of the electric field and the magnetic field. The kernels of the functionals are shown to be subject to thermodynamic restrictions which are of basic importance in wave propagation and initial boundary value problems. The non-uniqueness of the free enthalpy is examined and exemplified. The maximal free enthalpy is determined thus showing that the Clausius–Duhem inequality may hold as an equality also for systems with memory.
EXISTENCE OF SOLUTION TO NONLINEAR ELLIPTIC SYSTEMS ARISING IN TURBULENCE MODELLING
Authors: MÁRMOL MACARENA GÓMEZ , GALLEGO FRANCISCO ORTEGÓN
Published: April 2003

We study some nonlinear elliptic systems governing the steady-state of a two-equation turbulence model that has been derived from the so-called k–ε model. Two kinds of problems are considered: in the first one, we drop out transport terms and we deduce the existence of a solution for [Formula: see text]; in the second one we take into account all transport terms; in this case, the existence result holds for N=2 or 3. Positivity and [Formula: see text]-regularity of the scalar quantities are also shown here.
SEMICLASSICAL LIMIT OF THE DERIVATIVE NONLINEAR SCHRÖDINGER EQUATION
Authors: DESJARDINS BENOÎT , LIN CHI-KUN , TSO TAI-CHENG
Published: April 2003

We study the semiclassical limit of the general derivative nonlinear Schrödinger equation for initial data with Sobolev regularity, before shocks appear in the limit system. The strict hyperbolicity and genuine nonlinearity is proved for the dispersion limit of the derivative nonlinear Schrödinger equation.