An adaptive communication mechanism for heterogeneous distributed environments using XML and servlets.

Cheung Wing Hang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 107-112).Abstracts in English and Chinese.Abstract --- p.iiAbstract in Chinese --- p.ivAcknowledgments --- p.vChapter 1 --- Introduction --- p.1Chapter 1.1 --- Firewall Issue in Distributed Systems --- p.2Chapter 1.2 --- Heterogeneous Communication Protocols --- p.4Chapter 1.3 --- Translator for Converting Interface Definition to Flexible XML --- p.8Chapter 1.4 --- An Implementation of a Scalable Mediator Query System --- p.9Chapter 1.5 --- Our Contributions --- p.9Chapter 1.6 --- Outline of This Thesis --- p.10Chapter 2 --- Related Work and Technologies --- p.12Chapter 2.1 --- Overview of XML Technology --- p.12Chapter 2.1.1 --- XML Basic Syntax --- p.13Chapter 2.1.2 --- DTD: The Grammar Book --- p.15Chapter 2.1.3 --- Representing Complex Data Structures --- p.17Chapter 2.2 --- Overview of Java Servlet Technology --- p.18Chapter 2.3 --- Overview of Simple Object Access Protocol --- p.20Chapter 2.4 --- Overview of XML-RPC --- p.21Chapter 2.5 --- Overview of XIOP --- p.22Chapter 3 --- Using XML and Servlets to Support CORBA Calls --- p.24Chapter 3.1 --- Objective --- p.24Chapter 3.2 --- General Concept of Our Mechanism --- p.25Chapter 3.2.1 --- At Client Side --- p.27Chapter 3.2.2 --- At Server Side --- p.28Chapter 3.3 --- Data in Transmission --- p.30Chapter 3.3.1 --- Using XML --- p.30Chapter 3.3.2 --- Format of Messages in Transmission --- p.30Chapter 3.4 --- Supporting Callbacks in CORBA Systems --- p.33Chapter 3.4.1 --- What is callback? --- p.33Chapter 3.4.2 --- Enhancement to Allow Callbacks --- p.34Chapter 3.5 --- Achieving Transparency with Add-on Components --- p.37Chapter 4 --- A Translator to Convert CORBA IDL to XML --- p.39Chapter 4.1 --- Introduction to CORBA IDL --- p.39Chapter 4.2 --- Mapping from IDL to XML --- p.40Chapter 4.2.1 --- IDL Basic Data Types --- p.41Chapter 4.2.2 --- IDL Complex Data Types --- p.42Chapter 4.2.3 --- IDL Interface --- p.48Chapter 4.2.4 --- Attributes --- p.48Chapter 4.2.5 --- Operations (Methods) --- p.49Chapter 4.2.6 --- Exceptions --- p.50Chapter 4.2.7 --- Inheritance --- p.51Chapter 4.2.8 --- IDL Modules --- p.52Chapter 4.2.9 --- A Sample Conversion --- p.52Chapter 4.3 --- Making a Request or Response --- p.53Chapter 4.4 --- Code Generation for Add-on Components --- p.54Chapter 4.4.1 --- Generation of Shadow Objects --- p.54Chapter 4.4.2 --- Generation of Servlet Components --- p.55Chapter 5 --- Communication in Heterogeneous Distributed Environments --- p.58Chapter 5.1 --- Objective --- p.58Chapter 5.2 --- General Concept --- p.60Chapter 5.3 --- Case Study 1 - Distributed Common Object Model --- p.61Chapter 5.3.1 --- Brief Overview of Programming in DCOM --- p.61Chapter 5.3.2 --- Mapping the Two Different Interface Definitions --- p.63Chapter 5.3.3 --- Sample Architecture of Communicating Between DCOM and CORBA --- p.66Chapter 5.4 --- Case Study 2 - Java Remote Methods Invocation --- p.67Chapter 5.4.1 --- Brief Overview of Programming in Java RMI --- p.67Chapter 5.4.2 --- Mapping the Two Different Interface Definitions --- p.69Chapter 5.4.3 --- Sample Architecture of Communicating Between JavaRMI and CORBA --- p.71Chapter 5.5 --- Be Generic: Binding with the WEB --- p.72Chapter 6 --- Building a Scalable Mediator-based Query System --- p.74Chapter 6.1 --- Objectives --- p.74Chapter 6.2 --- Introduction to Our Mediator-based Query System --- p.76Chapter 6.2.1 --- What is mediator? --- p.76Chapter 6.2.2 --- The Architecture of our Mediator Query System --- p.77Chapter 6.2.3 --- The IDL Design of the Mediator System --- p.79Chapter 6.2.4 --- Components in the Query Mediator System --- p.80Chapter 6.3 --- Helping the Mediator System to Expand Across the Firewalls --- p.83Chapter 6.3.1 --- Implementation --- p.83Chapter 6.3.2 --- Across Heterogeneous Systems with DTD --- p.87Chapter 6.4 --- Adding the Callback Feature to the Mediator System --- p.89Chapter 6.5 --- Connecting our CORBA System with Other Environments --- p.90Chapter 6.5.1 --- Our Query System in DCOM --- p.91Chapter 6.5.2 --- Our Query System in Java RMI --- p.92Chapter 6.5.3 --- Binding Heterogeneous Systems --- p.93Chapter 7 --- Evaluation --- p.95Chapter 7.1 --- Performance Statistics --- p.95Chapter 7.1.1 --- Overhead in other methods --- p.97Chapter 7.2 --- Means for Enhancement --- p.98Chapter 7.2.1 --- Connection Performance of HTTP --- p.98Chapter 7.2.2 --- Transmission Data Compression --- p.99Chapter 7.2.3 --- Security Concern --- p.99Chapter 7.3 --- Advantages of Using Our Mechanism --- p.101Chapter 7.4 --- Disadvantages of Using Our Mechanism --- p.102Chapter 8 --- Conclusion --- p.10

Robotics software frameworks for multi-agent robotic systems development

Robotics is an area of research in which the paradigm of Multi-Agent Systems (MAS) can prove to be highly useful. Multi-Agent Systems come in the form of cooperative robots in a team, sensor networks based on mobile robots, and robots in Intelligent Environments, to name but a few. However, the development of Multi-Agent Robotic Systems (MARS) still presents major challenges. Over the past decade, a high number of Robotics Software Frameworks (RSFs) have appeared which propose some solutions to the most recurrent problems in robotics. Some of these frameworks, such as ROS, YARP, OROCOS, ORCA, Open-RTM, and Open-RDK, possess certain characteristics and provide the basic infrastructure necessary for the development of MARS. The contribution of this work is the identification of such characteristics as well as the analysis of these frameworks in comparison with the general-purpose Multi-Agent System Frameworks (MASFs), such as JADE and Mobile-C.Ministerio de Ciencia e Innovación TEC2009-10639-C04-02Junta de Andalucía P06-TIC-2298Junta de Andalucía P08-TIC-0386

Domain architecture a design framework for system development and integration

The ever growing complexity of software systems has revealed many short-comings in existing software engineering practices and has raised interest in architecture-driven software development. A system\u27s architecture provides a model of the system that suppresses implementation detail, allowing the architects to concentrate on the analysis and decisions that are most critical to structuring the system to satisfy its requirements. Recently, interests of researchers and practi-tioners have shifted from individual system architectures to architectures for classes of software systems which provide more general, reusable solutions to the issues of overall system organization, interoperability, and allocation of services to system components. These generic architectures, such as product line architectures and domain architectures, promote reuse and interoperability, and create a basis for cost effective construction of high-quality systems. Our focus in this dissertation is on domain architectures as a means of development and integration of large-scale, domain-specific business software systems. Business imperatives, including flexibility, productivity, quality, and ability to adapt to changes, have fostered demands for flexible, coherent and enterprise--wide integrated business systems. The components of such systems, developed separately or purchased off the shelf, need to cohesively form an overall compu-tational environment for the business. The inevitable complexity of such integrated solutions and the highly-demanding process of their construction, management, and evolution support require new software engineering methodologies and tools. Domain architectures, prescribing the organization of software systems in a business domain, hold a promise to serve as a foundation on which such integrated business systems can be effectively constructed. To meet the above expectations, software architectures must be properly defined, represented, and applied, which requires suitable methodologies as well as process and tool support. Despite research efforts, however, state-of-the-art methods and tools for architecture-based system development do not yet meet the practical needs of system developers. The primary focus of this dissertation is on developing methods and tools to support domain architecture engineering and on leveraging architectures to achieve improved system development and integration in presence of increased complexity. In particular, the thesis explores issues related to the following three aspects of software technology: system complexity and software architectures as tools to alleviate complexity; domain architectures as frameworks for construction of large scale, flexible, enterprise-wide software systems; and architectural models and representation techniques as a basis for good” design. The thesis presents an archi-tectural taxonomy to help categorize and better understand architectural efforts. Furthermore, it clarifies the purpose of domain architectures and characterizes them in detail. To support the definition and application of domain architectures we have developed a method for domain architecture engineering and representation: GARM-ASPECT. GARM, the Generic Architecture Reference Model, underlying the method, is a system of modeling abstractions, relations and recommendations for building representations of reference software architectures. The model\u27s focus on reference and domain architectures determines its main distinguishing features: multiple views of architectural elements, a separate rule system to express constraints on architecture element types, and annotations such as “libraries” of patterns and “logs” of guidelines. ASPECT is an architecture description language based on GARM. It provides a normalized vocabulary for representing the skeleton of an architecture, its structural view, and establishes a framework for capturing archi-tectural constraints. It also allows extensions of the structural view with auxiliary information, such as behavior or quality specifications. In this respect, ASPECT provides facilities for establishing relationships among different specifications and gluing them together within an overall architectural description. This design allows flexibility and adaptability of the methodology to the specifics of a domain or a family of systems. ASPECT supports the representation of reference architectures as well as individual system architectures. The practical applicability of this method has been tested through a case study in an industrial setting. The approach to architecture engineering and representation, presented in this dissertation, is pragmatic and oriented towards software practitioners. GARM-ASPECT, as well as the taxonomy of architectures are of use to architects, system planners and system engineers. Beyond these practical contributions, this thesis also creates a more solid basis for expbring the applicability of architectural abstractions, the practicality of representation approaches, and the changes required to the devel-opment process in order to achieve the benefits from an architecture-driven software technology

Flexible Scheduling in Middleware for Distributed rate-based real-time applications - Doctoral Dissertation, May 2002

Distributed rate-based real-time systems, such as process control and avionics mission computing systems, have traditionally been scheduled statically. Static scheduling provides assurance of schedulability prior to run-time overhead. However, static scheduling is brittle in the face of unanticipated overload, and treats invocation-to-invocation variations in resource requirements inflexibly. As a consequence, processing resources are often under-utilized in the average case, and the resulting systems are hard to adapt to meet new real-time processing requirements. Dynamic scheduling offers relief from the limitations of static scheduling. However, dynamic scheduling offers relief from the limitations of static scheduling. However, dynamic scheduling often has a high run-time cost because certain decisions are enforced on-line. Furthermore, under conditions of overload tasks can be scheduled dynamically that may never be dispatched, or that upon dispatch would miss their deadlines. We review the implications of these factors on rate-based distributed systems, and posits the necessity to combine static and dynamic approaches to exploit the strengths and compensate for the weakness of either approach in isolation. We present a general hybrid approach to real-time scheduling and dispatching in middleware, that can employ both static and dynamic components. This approach provides (1) feasibility assurance for the most critical tasks, (2) the ability to extend this assurance incrementally to operations in successively lower criticality equivalence classes, (3) the ability to trade off bounds on feasible utilization and dispatching over-head in cases where, for example, execution jitter is a factor or rates are not harmonically related, and (4) overall flexibility to make more optimal use of scarce computing resources and to enforce a wider range of application-specified execution requirements. This approach also meets additional constraints of an increasingly important class of rate-based systems, those with requirements for robust management of real-time performance in the face of rapidly and widely changing operating conditions. To support these requirements, we present a middleware framework that implements the hybrid scheduling and dispatching approach described above, and also provides support for (1) adaptive re-scheduling of operations at run-time and (2) reflective alternation among several scheduling strategies to improve real-time performance in the face of changing operating conditions. Adaptive re-scheduling must be performed whenever operating conditions exceed the ability of the scheduling and dispatching infrastructure to meet the critical real-time requirements of the system under the currently specified rates and execution times of operations. Adaptive re-scheduling relies on the ability to change the rates of execution of at least some operations, and may occur under the control of a higher-level middleware resource manager. Different rates of execution may be specified under different operating conditions, and the number of such possible combinations may be arbitrarily large. Furthermore, adaptive rescheduling may in turn require notification of rate-sensitive application components. It is therefore desirable to handle variations in operating conditions entirely within the scheduling and dispatching infrastructure when possible. A rate-based distributed real-time application, or a higher-level resource manager, could thus fall back on adaptive re-scheduling only when it cannot achieve acceptable real-time performance through self-adaptation. Reflective alternation among scheduling heuristics offers a way to tune real-time performance internally, and we offer foundational support for this approach. In particular, run-time observable information such as that provided by our metrics-feedback framework makes it possible to detect that a given current scheduling heuristic is underperforming the level of service another could provide. Furthermore we present empirical results for our framework in a realistic avionics mission computing environment. This forms the basis for guided adaption. This dissertation makes five contributions in support of flexible and adaptive scheduling and dispatching in middleware. First, we provide a middle scheduling framework that supports arbitrary and fine-grained composition of static/dynamic scheduling, to assure critical timeliness constraints while improving noncritical performance under a range of conditions. Second, we provide a flexible dispatching infrastructure framework composed of fine-grained primitives, and describe how appropriate configurations can be generated automatically based on the output of the scheduling framework. Third, we describe algorithms to reduce the overhead and duration of adaptive rescheduling, based on sorting for rate selection and priority assignment. Fourth, we provide timely and efficient performance information through an optimized metrics-feedback framework, to support higher-level reflection and adaptation decisions. Fifth, we present the results of empirical studies to quantify and evaluate the performance of alternative canonical scheduling heuristics, across a range of load and load jitter conditions. These studies were conducted within an avionics mission computing applications framework running on realistic middleware and embedded hardware. The results obtained from these studies (1) demonstrate the potential benefits of reflective alternation among distinct scheduling heuristics at run-time, and (2) suggest performance factors of interest for future work on adaptive control policies and mechanisms using this framework

Online failure prediction in air traffic control systems

This thesis introduces a novel approach to online failure prediction for mission critical distributed systems that has the distinctive features to be black-box, non-intrusive and online. The approach combines Complex Event Processing (CEP) and Hidden Markov Models (HMM) so as to analyze symptoms of failures that might occur in the form of anomalous conditions of performance metrics identified for such purpose. The thesis presents an architecture named CASPER, based on CEP and HMM, that relies on sniffed information from the communication network of a mission critical system, only, for predicting anomalies that can lead to software failures. An instance of Casper has been implemented, trained and tuned to monitor a real Air Traffic Control (ATC) system developed by Selex ES, a Finmeccanica Company. An extensive experimental evaluation of CASPER is presented. The obtained results show (i) a very low percentage of false positives over both normal and under stress conditions, and (ii) a sufficiently high failure prediction time that allows the system to apply appropriate recovery procedures

Online failure prediction in air traffic control systems

This thesis introduces a novel approach to online failure prediction for mission critical distributed systems that has the distinctive features to be black-box, non-intrusive and online. The approach combines Complex Event Processing (CEP) and Hidden Markov Models (HMM) so as to analyze symptoms of failures that might occur in the form of anomalous conditions of performance metrics identified for such purpose. The thesis presents an architecture named CASPER, based on CEP and HMM, that relies on sniffed information from the communication network of a mission critical system, only, for predicting anomalies that can lead to software failures. An instance of Casper has been implemented, trained and tuned to monitor a real Air Traffic Control (ATC) system developed by Selex ES, a Finmeccanica Company. An extensive experimental evaluation of CASPER is presented. The obtained results show (i) a very low percentage of false positives over both normal and under stress conditions, and (ii) a sufficiently high failure prediction time that allows the system to apply appropriate recovery procedures

Current Trends and New Challenges of Databases and Web Applications for Systems Driven Biological Research

Dynamic and rapidly evolving nature of systems driven research imposes special requirements on the technology, approach, design and architecture of computational infrastructure including database and Web application. Several solutions have been proposed to meet the expectations and novel methods have been developed to address the persisting problems of data integration. It is important for researchers to understand different technologies and approaches. Having familiarized with the pros and cons of the existing technologies, researchers can exploit its capabilities to the maximum potential for integrating data. In this review we discuss the architecture, design and key technologies underlying some of the prominent databases and Web applications. We will mention their roles in integration of biological data and investigate some of the emerging design concepts and computational technologies that are likely to have a key role in the future of systems driven biomedical research

Generic Distribution Support for Programming Systems

This dissertation provides constructive proof, through the implementation of a middleware, that distribution transparency is practical, generic, and extensible. Fault tolerant distributed services can be developed by using the failure detection abilities of the middleware. By generic we mean that the middleware can be used for many different programming languages and paradigms. Distribution for each kind of language entity is done in terms of consistency protocols, which guarantee that the semantics of the entities are preserved in a distributed setting. The middleware allows new consistency protocols to be added easily. The efficiency of the middleware and the ease of integration are shown by coupling the middleware to a programming system, which encompasses the object oriented, the functional, and the concurrent-declarative programming paradigms. Our measurements show that the distribution middleware is competitive with the most popular distributed programming systems (JavaRMI, .NET, IBM CORBA)

Composing Systemic Aspects into Component-Oriented DOC Middleware

The advent and maturation of component-based middleware frameworks have sim-plified the development of large-scale distributed applications by separating system devel-opment and configuration concerns into different aspects that can be specified and com-posed at various stages of the application development lifecycle. Conventional component middleware technologies, such as J2EE [73] and .NET [34], were designed to meet the quality of service (QoS) requirements of enterprise applications, which focus largely on scalability and reliability. Therefore, conventional component middleware specifications and implementations are not well suited for distributed real-time and embedded (DRE) ap-plications with more stringent QoS requirements, such as low latency/jitter, timeliness, and online fault recovery. In the DRE system development community, a new generation of enhanced commercial off-the-shelf (COTS) middleware, such as Real-time CORBA 1.0 (RT-CORBA)[39], is increasingly gaining acceptance as (1) the cost and time required to develop and verify DRE applications precludes developers from implementing complex DRE applications from scratch and (2) implementations of standard COTS middleware specifications mature and encompass key QoS properties needed by DRE systems. However, although COTS middleware standardizes mechanisms to configure and control underlying OS support for an application’s QoS requirements, it does not yet provide sufficient abstractions to separate QoS policy configurations such as real-time performance requirements, from application functionality. Developers are therefore forced to configure QoS policies in an ad hoc way, and the code to configure these policies is often scattered throughout and tangled with other parts of a DRE system. As a result, it is hard for developers to configure, validate, modify, and evolve complex DRE systems consistently. It is therefore necessary to create a new generation of QoS-enabled component middleware that provides more comprehensive support for addressing QoS-related concerns modularly, so that they can be introduced and configured as separate systemic aspects. By analyzing and identifying the limitations of applying conventional middleware technologies for DRE applications, this dissertation presents a new design and its associated techniques for enhancing conventional component-oriented middleware to provide programmability of DRE relevant real-time QoS concerns. This design is realized in an implementation of the standard CORBA Component Model (CCM) [38], called the Component-Integrated ACE ORB (CIAO). This dissertation also presents both architectural analysis and empirical results that demonstrate the effectiveness of this approach. This dissertation provides three contributions to the state of the art in composing systemic behaviors into component middleware frameworks. First, it illustrates how component middleware can simplify development and evolution of DRE applications while ensuring stringent QoS requirements by composing systemic QoS aspects. Second, it contributes to the design and implementation of QoS-enabled CCM by analyzing and documenting how systemic behaviors can be composed into component middleware. Finally, it presents empirical and analytical results to demonstrate the effectiveness and the advantage of composing systemic behaviors in component middleware. The work in this dissertation has a broader impact beyond the CCM in which it was developed, as it can be applied to other component-base middleware technologies which wish to support DRE applications