38191842
Modeling of End-to-End Transmission of Astronomical Images over Lossy Network
2048896
The Use of Parallel Processing to Achieve Decentralized Control of a Segmented Reflector Telescope
15990035
Content-based retransmission for 3-D wavelet video streaming on the Internet
Improving the QoS of video streaming with packet loss is a challenging topic of research. In this paper, we propose a novel content-based retransmission scheme to address this issue. The basic idea is to jointly consider the packets' contents and the channel conditions to optimize QoS. The goal is to deliver the best quality of video possible under the same channel condition. Using the proposed retransmission scheme, we have designed a 3D wavelet video streaming system. Simulation results show that the content-based retransmission can improve the video quality by more than 2 dB compared with the existing non-content-based delay-constrained retransmission when the channel loss rate is high.
17418612
Visualizing design patterns with a UML profile
In this paper, we present a UML profile which defines new stereotypes, tagged values and constraints for visualizing design patterns in UML diagrams. These new stereotypes and tagged values are attached to a modeling element to explicitly represent the role the modeling element plays in a design pattern so that the user can identify the pattern in a UML diagram.
6426341
Event-based blackboard architecture for multi-agent systems
Developing large multi-agent systems is a complex task involving the processes of the requirement, architecture, design and implementation of these systems. In particular, the architectural design is critical to cope with the increasing size and complexity of these systems. The multi-agent system that accesses a central repository is typically based on the blackboard architectural pattern. However, the control strategies of the agents are inherently complex. In this paper, we present an event-based control strategy to manage the access of central repository by multi-agents. In this approach, the blackboard pattern is composed with the implicit invocation pattern to separate the control policies from the control component so that the architecture is ease of evolution, reuses and changes.
16840990
Automating the analysis of design component contracts
Software patterns are a new design paradigm used to solve problems that arise when developing software within a particular context. Patterns capture the static and dynamic structure and collaboration among the components in a software design. A key promise of the pattern-based approach is that it may greatly simplify the construction of software systems out of building blocks and thus reuse experience and reduce cost. However, it also introduces significant problems in ensuring the integrity and reliability of these composed systems because of their complex software topologies, interactions and transactions. There is a need to capture these features as a contract through a formal model that allows us to analyze pattern-based designs. In this paper, we provide an overview of a formal framework for ensuring the integrity of the compositions in object-oriented designs by providing mathematically rigorous modeling and analysis techniques for object-oriented systems comprising pattern-based designs as the basic building blocks or design components. A case study related to a hypermedia Web-based application has been presented to illustrate our approach in distributed systems. Copyright © 2005 John Wiley & Sons, Ltd.
8741871
Living with free type and class union
There are two constructs in the formal specification language Object-Z for modelling polymorphic and recursive structures. One construct, the free type, is adopted from the Z specification language. The other, class-union, facilitates polymorphic class declarations. Free type and class-union constructs are respectively based upon the functional value point of view and the object reference point of view. Consequently, the roles these two constructs perform in system modelling are different. The free type and class-union constructs are compared and discussed through various examples. The aim of this comparison and discussion is to present guidelines on how to appropriately and effectively use these two constructs to specify polymorphic and recursive structures.
15881034
Network Topology and a Case Study in TCOZ
Object-Z is strong in modeling the data and operations of complex systems. However, it is weak in specifying real-time and concurrent systems. Timed Communicating Object-Z (TCOZ) extends the Object-Z notation with Timed CSP constructs. TCOZ is particularly well suited for specifying complex systems whose components have their own thread of control. This paper demonstrates expressiveness of the TCOZ notation through a case study on specifying a multi-lift system that operates in real-time.