5960532
Detecting Unsafe Error Recovery Schedules
A mechanism for modeling timing, precedence, and data-consistency constraints on concurrently executing processes is presented. The model allows durations and intervals between events to be specified. An algorithm is provided to detect schedules which may be unsafe with respect to the constraints. This work, motivated by the design and validation of autonomous error-recovery strategies on the Galileo spacecraft, appears to be applicable to a variety of asynchronous real-time systems. >
45515179
Distributed real-time nested transactions
Abstract We present the concepts of real-time nested transactions and priority propagation for a distributed transaction processing environment. Real-time nested transactions incorporate the deadline requirements in the hierarchical structure of nested transactions. Priority propagation addresses issues related to transaction aborts in real-time nested transaction processing. The notion of priority ceiling has been used to avoid the priority inversion problem. The proposed protocols exhibit freedom from deadlock and have tightly bounded waiting periods. Both of these properties make them very suitable for distributed real-time transaction processing environments.
19086803
Transaction management in design databases
Abstract Conventional data base systems are not suitable for handling advanced applications encountered in engineering, such as CAD/CAM, CASE, CAE, and VLSI design. The data bases in such environments, also called design data bases, are characterized by the presence of many complex data objects denoted by a large number of small tables, as opposed to a few large tables encountered in conventional data bases. The transaction model used in tracking data bases for banking, inventory control, and other such applications use view serializability as the correctness criterion. While view serializability is appropriate for tracking data bases, it is unnecessarily restrictive for engineering data bases. We propose a transaction model that is suitable for accessing shared design data based on coserializability. The transaction model supports long-duration transactions with intermediate commit points. In addition to the conventional nested transaction hierarchy, the model allows for cooperation between nested design transactions needed in a design environment.
44084630
Distributed and Fail-Safe Routing Algorithms in Toroidal-Based Metropolitan Area Networks
Abstract A two-dimensional toroidal network is simply a rectangular mesh where opposite nodes on the left and right boundaries are connected to each other and opposite nodes on the upper and lower boundaries are also connected to each other. Examples of toroidal based metropolitan area networks are HR 4 -NET and Manhattan Street Network (MSN). The original routing algorithm for HR 4 -NET proposed by Borgonovo and Cadorin, however, does not direct packets through shortest paths. This paper presents shortest path routing algorithms for HR 4 -NET, which are distributed and fail-safe. These algorithms can also be applied to multiple traffic types. Simple routing rules that use of the regular structure of the network are compared to MSN.
8543519
Design and Implementation of National Engineering Education Delivery System
29262099
Transaction models for design environments
Abstract Design data bases used in the design of engineering artifacts have characteristics quite different from conventional data bases. While conventional data bases have, at any given time, a single correct value for each of object, design data bases, due to the presence of design alternates or versions, have available several correct versions of design objects. However, during a design process, when several design objects are involved, the different versions of each object chosen for the design has to be controlled such that they are compatible or version consistent. This article formalizes the notion of version consistency and proposes two transaction models for design processes, where the notion of version consistency itself is used as a basis for scheduling design transactions. A mechanism for enforcing version control is also presented.
45147395
Analysis of a Token Ring Protocol for Voice Transmission
Abstract For voice transmissions in a local-area network, it is desirable to have a small coefficient of variation for the interdeparture time of voice packets at the destination. This may be achieved by the proper design of the medium access protocol. A token ring protocol with provision for voice traffic is considered. An analytic model is developed to study the performance of this protocol with respect to voice traffic. Numerical results showing the effect of model parameters on interdeparture time are presented.
675655
Analysis of Broadcast Delivery in a Videotex System
Videotex is a system which provides users with low-cost real-time access to information. In such a system, user requests are forwarded to a service computer where the desired information is retrieved and sent back to the user. In this study, we investigate the response time behavior of a videotex system where information requested by one user is broadcast to all users. A novel queueing model for broadcast delivery is developed. Using this model, we first obtain an analytic expression for the mean response time, and then we develop an efficient algorithm for its computation. Numerical results illustrating the performance characteristics of broadcast delivery are presented.
2277541
ILP-based engineering change
We have developed a generic integer linear programming(ILP)-based engineering change(EC) methodology. The EC methodology has three components: enabling, fast, and preserving. Enabling EC provides a user with the means to specify the amount of flexibility and how this flexibility should be distributed throughout the solution so that one can guarantee that a specific set of EC demands can be satisfied while preserving the quality of the initially obtained solution. Fast EC conducts changes in a fraction of the time needed to solve the problem while preserving or in some cases improving the quality of the initial solution. Preserving EC maintains either user specified components of the solution or as much as possible of the initial solution while still guaranteeing an optimal solution to the altered problem instance. We applied the generic methodology to Boolean Satisfiability (SAT) problem. The effectiveness of all proposed approaches and algorithms is demonstrated on standard benchmarks.
6612620
Design techniques for sensor appliances: foundations and light compass case study
We propose the first systematic, sensor-centric approach for quantitative design of sensor network appliances. We demonstrate its use by designing light appliance devices and the associated middleware. We have developed five models which are required to make this problem tractable and to undertake the challenging task of designing light sensor appliances: i. physical world, ii. light sensor, iii. physical phenomenon, iv. appliance design, and v. computational model. With these models in place, we present the new design methodology that consists of two main steps: 1. a procedure for placement of individual sensors of the appliances, and 2. error minimization-based sensor data interpretation middleware. We have developed new optimization techniques for both tasks. A portable light sensor system was designed using the optimization intensive procedure, and its effectiveness demonstrated.
14348286
A Visual Model Approach for Parsing Colonoscopy Videos
Colonoscopy is an important screening procedure for colorectal cancer. During this procedure, the endoscopist visually inspects the colon. Currently, there is no content-based analysis and retrieval system that automatically analyzes videos captured from colonoscopic procedures and provides a user-friendly and efficient access to important content. Such a system will be valuable as an educational resource for endoscopic research, a platform to assess procedural skills for endoscopists, and a platform for mining for unknown abnormality patterns that may lead to colorectal cancer. The first necessary step for the analysis is parsing for semantic units. In this paper, we propose a new visual model approach that employs visual features extracted directly from compressed videos together with audio analysis to discover important semantic units called scenes. Our experimental results show average precision and recall of 93% and 85%, respectively.