Thesis (Ph.D.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

The purpose of this project was to explore the use of Web services to solve enterprise computing problems. XML-based Web services allow complex information systems to be subdivided. In order to explore this architectural paradigm, two systems were built: an employee records sytem, and a vacation system.

This thesis introduces a novel approach in which multiple heterogeneous devices collaborate to provide useful applications in an ad-hoc network. This thesis proposes a smart home as a particular ubiquitous computing scenario considering all the requirements given by the literature for succeed in this kind of systems. To that end, we envision a horizontally integrated smart home built up from independent components that provide services. These components are described with enough syntactic, semantic and pragmatic knowledge to accomplish spontaneous collaboration. The objective of these collaboration is domestic use, that is, the provision of valuable services for home residents capable of supporting users in their daily activities. Moreover, for the system to be attractive for potential customers, it should offer high levels of trust and reliability, all of them not at an excessive price. To achieve this goal, this thesis proposes to study the synergies available when an ontological description of home device functionality is paired with a formal method. We propose an ad-hoc home network in which components are home devices modelled as processes represented as semantic services by means of the Web Service Ontology (OWL-S). In addition, such services are specified, verified and implemented by means of the Communicating Sequential Processes (CSP), a process algebra for describing concurrent systems. The utilisation of an ontology brings the desired levels of knowledge for a system to compose services in a ad-hoc environment. Services are composed by a goal based system in order to satisfy user needs. Such system is capable of understaning, both service representations and user context information. Furthermore, the inclusion of a formal method contributes with additional semantics to check that such compositions will be correctly implemented and executed, achieving the levels of reliability and costs reduction (costs derived form the design, development and implementation of the system) needed for a smart home to succeed.

With the widespread use of the Internet and its associated technologies, enterprises have to evolve in the way they are conducting business. 'e-business applications' refer to a new class of distributed applications that involves the Internet as a communication platform. Each e-business application supports the full automation of business processes that can span across multiple enterprises. For a given application domain that involves e-business application development, a number of design decisions that best fullfil stakeholders requirements have to be made. One important issue is the reuse of functionality which exists within legacy systems that can belong to one or more enterprises within the same domain. Most existing design approaches are inadequate in supporting the exploration of all design combinations. Moreover, there is little work on how to identify the best design decisions systematically for a given application domain. In this thesis we present a pattern-based approach that addresses the architectural design of e-business applications. We identify a number of architectural patterns whose instantiation on a given design problem correspond to different architectural design alternatives. We also identify models that enable the estimation of quality attributes for such alternatives. Then we investigate and utilise methods to select the best pattern for a given design problem. We also describe the process of generating the alternative architectures, estimating their qualities, and then ranking them with respect to any quality attribute or a combination of quality attributes. We validate this approach on a real life case study in the area of capital markets. The case study concerns realistic e-business applications that rely on existing legacy applications. The validation exercise has produced predictions which have been compared with actual design decisions that have been made. The thesis also proposes a framework for the systematic identification of architectural patterns. An additional set of architectural patterns and their impact on the case study are discussed. The main contribution of this thesis is in the identification of patterns and quality attributes models for the architectural design of e-business applications that aid in the systematic selection of the most appropriate architectural pattern for a given problem context.

Complex distributed systems such as distributed information flows systems which continuously acquire manipulate and disseminate information across an enterprise's distributed sites and machines, and distributed server applications co-deployed in one or multiple shared data centers, with each of them having different performance/availability requirements that vary over time and competing with each other for the shared resources, have been playing a more serious role in industry and society now. Consequently, it becomes more important for enterprise scale IT infrastructure to provide timely and sustained/reliable delivery and processing of service requests. This hasn't become easier, despite more than 30 years of progress in distributed computer connectivity, availability and reliability, if not more difficult~cite{ReliableDistributedSys}, because of many reasons. Some of them are, the increasing complexity of enterprise scale computing infrastructure; the distributed nature of these systems which make them prone to failures, e.g., because of inevitable Heisenbugs in these complex distributed systems; the need to consider diverse and complex business objectives and policies including risk preference and attitudes in enterprise computing; the issues of performance and availability conflicts, varying importance of sub-systems in an enterprise's distributed infrastructure which compete for resource in currently typical shared environment; and the best effort nature of resources such as network resources, which implies resource availability itself an issue, etc. This thesis proposes a novel business policy-driven risk-based automated availability management which uses an automated decision engine to make various availability decisions and meet business policies while optimizing overall system utility, uses utility theory to capture users' risk attitudes, and address the potentially conflicting business goals and resource demands in enterprise scale distributed systems. For the critical and complex enterprise applications, since a key contributor to application utility is the time taken to recover from failures, we develop a novel proactive fault tolerance approach, which uses online methods for failure prediction to dynamically determine the acceptable amounts of additional processing and communication resources to be used (i.e., costs) to attain certain levels of utility and acceptable delays in failure recovery. Since resource availability itself is often not guaranteed in typical shared enterprise IT environments, this thesis provides IQ-Paths with probabilistic service guarantee, to address the dynamic network behavior in realistic enterprise computing environment. The risk-based formulation is used as an effective way to link the operational guarantees expressed by utility and enforced by the PGOS algorithm with the higher level business objectives sought by end users. Together, this thesis proposes novel availability management framework and methods for large-scale enterprise applications and systems, with the goal to provide different levels of performance/availability guarantees for multiple applications and sub-systems in a complex shared distributed computing infrastructure. More specifically, this thesis addresses the following problems. For data center environments, (1) how to provide availability management for applications and systems that vary in both resource requirements and in their importance to the enterprise, based both on operational level quantities and on business level objectives; (2) how to deal with managerial policies such as risk attitude; and (3) how to deal with the tradeoff between performance and availability, given limited resources in a typical data center. Since realistic business settings extend beyond single data centers, a second set of problems addressed in this thesis concerns predictable and reliable operation in wide area settings. For such systems, we explore (4) how to provide high availability in widely distributed operational systems with low cost fault tolerance mechanisms, and (5) how to provide probabilistic service guarantees given best effort network resources.