13004956
Consistency checking of UML requirements
This paper discusses how to check consistency of UML requirements model which consists of a use case model and a conceptual class model with system constraints. Based on a given semantics, the requirements consistency can be defined and checked formally. The consistency among use cases and constraints are classified into five types. A system operation of interaction between actor and system is formally defined as a pair of pre and post conditions. An atomic use case is described as one system operation, and a composed use case may be defined as several system operations described by an activity diagram. Thus, each use case can also be modelled as a pair of pre and post conditions by composing the pre and post conditions of system operations by introducing a sequence composition operation. Requirement consistency can be logically checked based on the semantics. A simple library system is used as a case study to illustrate the feasibility of the method.
7545798
Verification of fault tolerance and real time
A transformational method is given for specifying and verifying fault-tolerant, real-time programs. Such a program needs to be provably correct according to both its functional and real-time requirements, despite the possible occurrence of system failures. The paper demonstrates that a suitably expressive logic for real-time systems makes it possible to naturally model the state changes caused by system failures and determine their effect on the functional and real-time properties of executions.
216012840
Specification and verification of fault-tolerance, timing, and scheduling
Fault-tolerance and timing have often been considered to be implementation issues of a program, quite distinct from the functional safety and liveness properties. Recent work has shown how these no...
15986830
A formal semantics of UML sequence diagram
We present a formal semantics of UML sequence diagram. In abstract syntax form, a well-formed sequence diagram corresponds to an ordered hierarchical structure tree. The static semantics of a sequence diagram is to check whether it is consistent with the class diagram declaration as well as with its well-formed tree structure. Meanwhile, the dynamic semantics is defined in terms of the state transitions that are carried out by the method invocations in the diagram. When a message is executed, it must be consistent with system state, i.e., object diagram and the state diagrams of its related objects. The semantics clearly captures the consistency between sequence diagram with class diagram and state diagram. Therefore, it is useful to develop the model consistent checking functions in UML CASE tools. And it also can be used to reason about the correctness of a design model with respect to a requirement model.
206638919
Stepwise Development of Fault-Tolerant Reactive Systems
Consider a reactive system of the form S1 ∥ S2. Given the specification of one component, say S1, methods are available to design S2 in a stepwise manner such that the composed system S1 ∥ S2 satisfies a given specification. In this paper, we use a similar paradigm to construct a fault-tolerant program. Given a program S1 that may suffer from hardware faults or software design faults, we show how a stepwise method can be used to design a program S2 so that S1 ∥ S2 meets a given specification. The main idea is demonstrated by solving a resource allocation problem.
11711500
Verification of schedulability for real-time programs
Assume that a real-time programPT consisting of a number of parallel processes is executed on a system having a setPr of processors which are shared between the processes by a real-time schedulerST. Assume that PT must meet some timing deadlines. We show that such an implementation ofPT can be represented as a transformationL(PT) and that the deadlines ofPT will be met if they are satisfied by the timing properties of the transformed program. The condition for feasibility of a real-time program executed under a scheduler is formalized and rules are provided for verification. The schedulerST can be specifiedgenerically and applied to different programs, making it unnecessary to introduce low-level operations such as scheduling primitives into the programming language. Thus real-time program specification and Schedulability can be considered in the same framework and the timing properties of a program can be determined at the specification level. By separating the specification of the scheduler from that of the program, the feasibility of an implementation can be proved by considering a scheduling policy rather than its implementation details.
35062719
Vision Guided Circumnavigating Autonomous Robots
We present a system for vision guided autonomous circumnavigation, allowing a mobile robot to navigate safely around objects of arbitrary pose, and avoid obstacles. The system performs model-based object recognition from an intensity image. By enabling robots to recognize and navigate with respect to particular objects, this system empowers robots to perform deterministic actions on specific objects, rather than general exploration and navigation as emphasized in much of the current literature. This paper describes a fully integrated system, and, in particular, introduces canonical-views. Further, we derive a direct algebraic method for finding object pose and position for the four-dimensional case of a ground-based robot with uncalibrated vertical movement of its camera. Vision for mobile robots can be treated as a very different problem to traditional computer vision, as mobile robots have a characteristic perspective, and there is a causal relation between robot actions and view changes. Canonical-views are a novel, active object representation designed specifically to take advantage of the constraints of the robot navigation problem to allow efficient recognition and navigation.
7088840
Communication protection in IP-based video surveillance systems
For decades, video surveillance systems have been crucial in protecting critical infrastructures. Currently the systems are adopting the emerging internetworking digital technology, changing from the traditional isolated analog technology. While there are several advantages of IP-based video surveillance systems, the systems are also exposed to additional new security threats. Security is a critical factor to make the IP-based video surveillance systems practical and usable. In this paper, we address the security threats to the data communications in IP-based video surveillance systems. We first analyze the current approaches, mainly naive and selective methods, to secure real-time video data, and identify their limitations to IP-based video surveillance systems. Then we propose a system design of secure internetworking video surveillance systems. Our proposed approach adopts a randomly adjustable encryption method to provide confidentiality to the data. Our implementation and performance study demonstrate that our approach achieves a good balance of cost-efficiency and security.
3761715
A multicommodity flow model for distributed stream processing
The rapid development of computer technology has enabled streaming applications to emerge from many areas of the IT industry. A fundamental problem in such stream processing systems is how to best utilize the available resources so that the overall system performance is optimized. In most real time systems, applications are often running in a decentralized, distributed environment. At any given time, no server has the global information about all the servers in the system. It is thus desirable to have distributed solutions capable of adapting to or absorbing local changes in production rates and in network conditions. This paper addresses the fundamental resource allocation question in the distributed stream processing setting. Specifically, we consider a generic model for stream processing systems. Each stream is required to complete a series of tasks to become finished product. Each server is responsible for a subset of the processing tasks for possibly a subset of the streams. All servers have finite computing resources and all communication links have finite available bandwidth. We consider the resource allocation problem so as to maximize the total throughput of the system. Our problem can be described as a generalization of the traditional multicommodity flow problem [1]. Traditional multicommodity flow problem looks for the best way to use of the link capacities to deliver the maximum throughput for the flows in the whole network. In our problem, in addition to the link bandwidth constraints, we also have processing power constraints for each server. Furthermore, we allow flow shrinkage or expansion so as to model operations such
14922920
A dynamic trust model for mobile ad hoc networks
This paper introduces a trust model for mobile ad hoc networks. Initially each node is assigned a trust level. Then we use several approaches to dynamically update trust levels by using reports from threat detection tools, such as intrusion detection systems (IDS), located on all nodes in the network. The nodes neighboring to a node exhibiting suspicious behavior initiate trust reports. These trust reports are propagated through the network using one of our proposed methods. A source node can use the trust levels it establishes for other nodes to evaluate the security of routes to destination nodes. Using these trust levels as a guide, the source node can then select a route that meets the security requirements of the message to be transmitted. This paper demonstrates important concepts for establishing a collaborative, dynamic trust model and for using this model as an example to enhance the security of message routing in mobile ad hoc networks.
34025553
Security as services in active networks
This paper discusses the design and implementation for supporting customized security services in active networks using active networking principles. The customized security services support is based on a secure node architecture that includes an active node operating system security API, an active security guardian, and quality of protection provisions. The support of highly customized security services permits active nodes to satisfy the application-specific dynamic security and protection requirements. It associates quality of protection with network software and application security. Applications can dynamically select the suitable security configurations and services at each active routing node, based on their security and performance requirements. The secure node architecture, together with the support of dynamically customized security services, can provide a fundamental base for securing the active network infrastructure and active applications.