Management of object-oriented action-based distributed programs

Phd ThesisThis thesis addresses the problem of managing the runtime behaviour of distributed programs. The thesis of this work is that management is fundamentally an information processing activity and that the object model, as applied to actionbased distributed systems and database systems, is an appropriate representation of the management information. In this approach, the basic concepts of classes, objects, relationships, and atomic transition systems are used to form object models of distributed programs. Distributed programs are collections of objects whose methods are structured using atomic actions, i.e., atomic transactions. Object models are formed of two submodels, each representing a fundamental aspect of a distributed program. The structural submodel represents a static perspective of the distributed program, and the control submodel represents a dynamic perspective of it. Structural models represent the program's objects, classes and their relationships. Control models represent the program's object states, events, guards and actions-a transition system. Resolution of queries on the distributed program's object model enable the management system to control certain activities of distributed programs. At a different level of abstraction, the distributed program can be seen as a reactive system where two subprograms interact: an application program and a management program; they interact only through sensors and actuators. Sensors are methods used to probe an object's state and actuators are methods used to change an object's state. The management program is capable to prod the application program into action by activating sensors and actuators available at the interface of the application program. Actions are determined by management policies that are encoded in the management program. This way of structuring the management system encourages a clear modularization of application and management distributed programs, allowing better separation of concerns. Managemental concerns can be dealt with by the management program, functional concerns can be assigned to the application program. The object-oriented action-based computational model adopted by the management system provides a natural framework for the implementation of faulttolerant distributed programs. Object orientation provides modularity and extensibility through object encapsulation. Atomic actions guarantee the consistency of the objects of the distributed program despite concurrency and failures. Replication of the distributed program provides increased fault-tolerance by guaranteeing the consistent progress of the computation, even though some of the replicated objects can fail. A prototype management system based on the management theory proposed above has been implemented atop Arjuna; an object-oriented programming system which provides a set of tools for constructing fault-tolerant distributed programs. The management system is composed of two subsystems: Stabilis, a management system for structural information, and Vigil, a management system for control information. Example applications have been implemented to illustrate the use of the management system and gather experimental evidence to give support to the thesis.CNPq (Consellho Nacional de Desenvolvimento Cientifico e Tecnol6gico, Brazil): BROADCAST (Basic Research On Advanced Distributed Computing: from Algorithms to SysTems)

An approach to building a secure and persistent distributed object management system

The Common Object Request Broker Architecture (CORBA) proposed by the Object Management Group (OMG) is a widely accepted standard to provide a system level framework in design and implementation of distributed objects. The core of the Object Management Architecture (OMA) is an Object Request Broker (ORB), which provides transparency of object location, activation, and communications. However, the specification provided by the OMG is not sufficient. For instance, there are no security specifications when handling object requests through the ORBs. The lack of such a security service prevents the use of CORBA from handling sensitive data such as personal and corporate financial information; In view of the above, this thesis identifies, explores, and provides an approach to handling secure objects in a distributed environment along with a persistent object service using the CORBA specification. The research specifically involves the design and implementation of a secured distributed object service. This object service requires a persistent service and object storage for storing and retrieving security specific information. To provide a secure distributed object environment, a secure object service using the specifications provided by the OMG has been designed and implemented. In addition, to preserve the persistence of secure information, an object service has been implemented to provide a persistent data store; The secure object service can provide a framework for handling distributed object in applications requiring security clearance such as distributed banking, online stock tradings, internet shopping, geographic and medical information systems

Special Issue on Information Dissemination and New Services in P2P Systems

Information dissemination is an important P2P application that has received considerable research attention in recent years. P2P information dissemination systems range from simple file sharing applications to more complex systems that allows users to securely and efficiently publish, organize, index, search, update and retrieve data in a distributed storage medium. For complex P2P information dissemination systems, there is a need for features which include security, anonymity, fairness, scalability, resource management, and organization capabilities. For effective information dissemination, following features of P2P systems and infrastructure need to be updated: distributed object location and routing mechanisms, novel approaches to content replication, caching and migration, encryption, authentication, access control, and resource trading and management schemes

An Architecture for distributed multimedia database systems

In the past few years considerable demand for user oriented multimedia information systems has developed. These systems must provide a rich set of functionality so that new, complex, and interesting applications can be addressed. This places considerable importance on the management of diverse data types including text, images, audio and video. These requirements generate the need for a new generation of distributed heterogeneous multimedia database systems. In this paper we identify a set of functional requirements for a multimedia server considering database management, object synchronization and integration, and multimedia query processing. A generalization of the requirements to a distributed system is presented, and some of our current research and developing activities are discussed

Benchmarking real-time distributed object management systems for evolvable and adaptable command and control applications

Abstract This paper describes benchmarking for evolvable and adaptable real-time command and control systems Introduction MITRE's Evolvable Real-Time C3 initiative developed an approach that would enable current real-time systems to evolve into the systems of the future. We designed and implemented an infrastructure and data manager so that various applications could be hosted on the infrastructure. Then we completed a follow-on effort to design flexible adaptable distributed object management systems for command and control (C2) systems. Such an adaptable system would switch scheduling algorithms, policies, and protocols depending on the need and the environment. Both initiatives were carried out for the United States Air Force. One of the key contributions of our work is the investigation of real-time features for distributed object management systems. Partly as a result of our work we are now seeing various real-time distributed object management products being developed. In selecting a real-time distributed object management systems, we need to analyze various criteria. Therefore, we need benchmarking studies for realtime distributed object management systems. Although benchmarking systems such as Hartstone and Distributed Hartstone have been developed for middleware systems, these systems are not developed specifically for distributed object-based middleware. Since much of our work is heavily based on distributed objects, we developed benchmarking systems by adapting the Hartstone system. This paper describes out effort on developing benchmarks. In section 2 we discuss Distributed Hartstone. Then in section 3, we first provide background on the original Hartstone and DHartstone designs from SEI (Software Engineering Institute) and CMU (Carnegie Mellon University). We then describe our design and modification of DHartstone to incorporate the capability to benchmark real-time middleware in Section 4. Sections 5 and 6 describe the design of the benchmarking systems. For more details of our work on benchmarking and experimental results we refer to [MAUR98] and [MAUR99]. For background information of our work we refer t

Performance of distributed information systems

There is an increasing use of distributed computer systems to provide services in both traditional telephony as well as in the Internet. Two main technologies are Distributed Object Computing (DOC) and Web based services. One common DOC architecture investigated in this thesis is the Common Object Request Broker Architecture (CORBA), specified by the Object Management Group. CORBA applications consist of interacting software components called objects. Two other DOC architectures investigated are the Telecommunications Information Net- working Architecture (TINA) and a CORBA based Intelligent Network (IN/CORBA) system. In a DOC environment, the objects of an application are distributed on mul- tiple nodes. A middleware layer makes the distribution transparent to the application. However, the distributed nature creates a number of potential performance problems. Three problems in DOC systems are examined in this thesis: object distribution, load balancing and overload protection. An object distribution describes how objects are distributed in the network. The objective is to distribute the objects on the physical nodes in such a way that intern-node communication overhead is as small as possible. One way to solve the object distribution problem is to use linear programming. The constraints for the problem are then given by both ease of management of the system and performance concerns. Load balancing is used when there are multiple objects that can be used at a particular time. The objective of load balancing is to distribute the load e±ciently on the available nodes. This thesis investigates a number of de- centralized load balancing mechanisms, including one based on the use of intelligent agents. Finally, overload protection mechanisms for DOC systems are investigated. While overload protection is well-researched for telecom networks, only little work has been performed previously concerning DOC and overload protection. Also, this thesis examines the use of overload protection in e-commerce web servers. Two schemes are compared, one which handles admission to the e-commerce site on request basis, and another which handles admission on session basis. The session based mechanism is shown to be better in terms of user-experienced performance

MIS 830 Problems in Management Information Systems

Course syllabus for MIS 830A Problems in Management Information Systems Course description: Studies the role and application of computers in modern organizations. Discusses appropriate strategies for the effective utilization of computerized environment to improve productivity and efficiency of organizations, especially planning and control functions. Major thrust of the course is focused on the following concepts/assumptions: Information systems can provide competitive advantage to organizations and this recognition is important in corporate strategy formulation/implementation. Development and widespread corporate use of databases, Al/expert systems and client server technology have changed the nature and role of information systems. Recent technological advances (microcomputers, distributed systems, end user computing, local area networks, micro mainframe linkages, fourth generation software, multimedia computing, object-oriented programming, mobile computing, data warehousing, etc.) have made qualitative changes in the way information is acquired, processed, and used by organizations. Topics covered include the following: Conceptual Frameworks of MIS and DSS; Information Systems for Strategic Planning vs Operations Control; Prototyping Methodology; Use of Models in a Computerized Environment; Centralization vs Decentralization; Distributed Information Systems; Assessment of Information Requirements; Expert Systems and AI Applications; Executive Support Systems; Multimedia Computing; Mobile Computing; Client Server Technology; Imaging Systems, Data Warehousing, Feasibility, Design and Implementation of DSS; etc. The course attempts to provide an overview of modern technological and managerial developments in MIS and their impacts on corporate management and organizational structure. Case discussion will be used as the primary instructional format. The instructor will present selected MIS topics in a lecture format in each class session. Each student is required to prepare one or more assigned papers. A seminar approach will be used to examine the contents/significance of the assigned papers

Web-based Information Systems: Data Monitoring, Analysis and Reporting for Measurements and Simulations

This paper describes the concept, implementation and application of the Web-based Information System ‘Turtle’ for data monitoring, analysis, reporting and management in engineering projects. The system uses a generalised object-oriented approach for information modelling of physical state variables from measurements and simulations by sets of tensor objects and is implemented platform-independently as a Web application. This leads to a more flexible handling of measurement and simulation information in distributed and interdisciplinary engineering projects based on the concept of information sharing. The potential and advantages of Web-based information systems like ‘Turtle’ are described for one selected application example: a measurement programme dealing with the physical limnology of Lake Constance