Feedback mechanism validation and path query messages in label distribution protocol

In constraint based routing a topology database is maintained on all participating nodes to be used in calculating a path through the network. This database contains a list of the links in the network and the set of constraints the links can meet. Since these constraints change rapidly, the topology database will not be consistent with respect to the real network. A feedback mechanism was proposed by Ashwood-Smith, et al, to help correct the errors in the database. It behaves like a depth first search, and is meant to be useable only when the database sees the availability of resource more than there really are. In this mechanism, the source node can learn from the successes or failures of its path selections by receiving feedback from the path it is attempting. The received information is used in the subsequent path calculations. We validated the feedback algorithm to see how it behaves in all database situations, and found out that the feedback algorithm was helpful in all cases not only when it was optimistic. We also propose adding query messages to make the feedback algorithm behave more like breadth first search. The path query messages algorithm reduces the retry attempts in setting up a path, and also utilizes the network by gathering much more information about the resources

Fail-Safe Testing of Safety-Critical Systems

This dissertation proposes an approach for testing of safety-critical systems. It is based on a behavioral and a fault model. The two models are analyzed for compatibility and necessary changes are identified to make them compatible. Then transformation rules are used to transform the fault model into the same model type as the behavioral model. Integration rules define how to combine them. This approach results in an integrated model which then can be used to generate tests using a variety of testing criteria. The dissertation illustrates this general framework using a CEFSM for the behavioral model and a Fault Tree for the fault model. We apply the technique to a variety of applications such as a Gas burner, an Aerospace Launch System, and a Railroad Crossing Control System. We also investigate the scalability of the approach and compare its efficiency with integrating a state chart and a fault tree. Construction and Analysis of Distributed Processes (CADP) has been used as a supporting tool for this approach to generate test cases from the integrated model and to analyze the integrated model for some properties such as deadlock and livelock

Active World Model for Testing Autonomous Systems Using CEFSM

Abstract-This paper describes a model-based test generation approach for testing autonomous systems interacting with their environment (i.e., world). Unlike other approaches that assume a static world with attributes and values, we present and test a dynamic world. We use Communicating Extended Finite State Machine (CEFSM) to illustrate an active world model that describes behaviors of environmental factors (i.e., actors). Abstract World Behavioral Test Cases (AWBTCs) are then generated by covering the active world model using graph coverage criteria. We also generate test-data by input-space partitioning to transform the generated AWBTCs into executable test cases. We apply the World Model-based Test Generation (WMBTG) technique to a case study from the Human-Robot Interaction domain (HRI) specifically a tour-guide robot. Reachability of the active world model and efficiency of coverage criteria are also discussed

Fail-safe Testing of Safety-critical Systems: A Case Study and Efficiency Analysis

This paper proposes an approach for testing of safety-critical systems. It is based on a behavioral and a fault model. The two models are analyzed for compatibility, and necessary changes are identified to make them compatible. Then, transformation rules are used to transform the fault model into the same model type as the behavioral model. Integration rules define how to combine them. This approach results in an integrated model which then can be used to generate tests using a variety of testing criteria. The paper illustrates this general framework using a CEFSM for the behavioral model and a fault tree for the fault model. We apply the technique to an aerospace launch system. We also investigate the scalability of the approach and compare its efficiency with integrating a state chart and a fault tree