A scheme is presented that makes a remote procedure call (RPC) mechanism fault-tolerant to hardware failures. Fault tolerance is provided by replicating the procedure at a group of nodes, called a cluster. The copies ...
详细信息
A scheme is presented that makes a remote procedure call (RPC) mechanism fault-tolerant to hardware failures. Fault tolerance is provided by replicating the procedure at a group of nodes, called a cluster. The copies in a cluster are linearly ordered. A call to a procedure is sent to the first copy in the cluster and is propagated internally to all other copies. In the event of failures, the first copy in the cluster that has not failed returns the result to the caller. The scheme is transparent to the user and supports nested procedure calls. It has been implemented on a network of Sun workstations making use of Sun's existing RPC mechanism.< >
The authors present a simple strategy for generating testcases for implementations of abstract data types, based on syntactic information about the operations on the type. The developed tool has been used on a number ...
详细信息
The authors present a simple strategy for generating testcases for implementations of abstract data types, based on syntactic information about the operations on the type. The developed tool has been used on a number of different types including stacks, strings, etc. It is found that choosing depth 2 for generating the testcases results in an effective set of testcases for detecting errors and can provide 100% statement coverage if proper initial values are selected. There are no rules for selecting the initial values.< >
The PFG language is a parallel programming language with graphical syntax. Its formal operational semantics are expressed by the HG model of concurrent real-time software systems. Informally, each procedure in a PFG p...
详细信息
The PFG language is a parallel programming language with graphical syntax. Its formal operational semantics are expressed by the HG model of concurrent real-time software systems. Informally, each procedure in a PFG program is a hierarchical graph expressing the data state and a place-timed Petri net expressing the possible parallel threads of control operating the data state. The author demonstrates how the PFG language, which is sufficient in itself for software construction, can be used as a kernel language for the implementation of higher-level languages. PFG can then be thought of as a graphical assembly language, with the HG model being the virtual machine.< >
The author discusses PFG (parallel flow graphs), a hardware/software system modeling language and support environment based on a concurrent, place-timed deterministic Petri net formalism termed the HG (hierarchical gr...
详细信息
The author discusses PFG (parallel flow graphs), a hardware/software system modeling language and support environment based on a concurrent, place-timed deterministic Petri net formalism termed the HG (hierarchical graph) model of time-dependent concurrent systems. The HG model serves as the formal semantics of computation for the PFG language, which has a graphical syntax and serves as a composition vehicle for Petri nets that have interpretable form and limited complexity. The PFG environment is a collection of cooperating tools that operate on these HG models for the production of reliable time-dependent software systems from reusable components. Algorithms that have been developed for analysis of the HG formalism include detection and correction of improper access to shared data, calculation of minimum and maximum execution time bounds, and matching of models to graphical specification templates for reuse.< >
One attempt at explaining human inferencing is that of spreading activation, particularly in the structured connectionist paradigm. This has resulted in the building of systems with semantically nameable nodes which p...
One attempt at explaining human inferencing is that of spreading activation, particularly in the structured connectionist paradigm. This has resulted in the building of systems with semantically nameable nodes which perform inferencing by examining the patterns of activation spread. In this paper we demonstrate that simple structured network inferencing can be performed by passing activation over the weights learned by a distributed algorithm. Thus, an account, is provided which explains a well-behaved relationship between structured and distributed connectionist approaches.
A study is performed of the problem of planning a collision-free path for a robot in a time-varying environment. It is assumed that an obstacle moves along a known path. The formulation also allows the destination poi...
详细信息
A study is performed of the problem of planning a collision-free path for a robot in a time-varying environment. It is assumed that an obstacle moves along a known path. The formulation also allows the destination point (the point to be reached) to move along a predetermined path. A concept of 'accessibility' from a point to a moving object is introduced and is used to determine a collision-free path. An environment which contains some uncertainty in which the robot needs to see and possibly plan an alternative path is also considered. The ability to deal with moving obstacles is useful in a variety of visual tasks such as the navigation of an autonomous vehicle and the interaction between robot arms.< >
A study comparing the speed, accuracy, and user satisfaction of three different touch screen strategies was performed. The purpose of the experiment was to evaluate the merits of the more intricate touch strategies th...
详细信息
ISBN:
(纸本)0201142376
A study comparing the speed, accuracy, and user satisfaction of three different touch screen strategies was performed. The purpose of the experiment was to evaluate the merits of the more intricate touch strategies that are possible on touch screens that return a continuous stream of touch data. The results showed that a touch strategy providing continuous feedback until a selection was confirmed had fewer errors than other touch strategies. The implications of the results for touch screens containing small, densely-packed targets were discussed.
A concurrent computer-integrated manufacturing (CIM) system modeling technique, called hierarchical graph (HG) modeling, is presented, along with its language extension, called parallel flow graph (PFG). HG is an abst...
详细信息
A concurrent computer-integrated manufacturing (CIM) system modeling technique, called hierarchical graph (HG) modeling, is presented, along with its language extension, called parallel flow graph (PFG). HG is an abstract parallel machine, that is, a model of concurrent computation, that can be used to describe the logical structure of a CIM system and the relationships among each subsystem and the global control system. In particular, HG is capable of defining each subsystem and composing them hierarchically to realized a complex CIM system. The HG formalism is based on a three-part division of computation along logical boundaries: a data model based on hierarchical graphs, a static program model of basic instruction blocks, and a control-flow model based on timed Petri nets. Using an analysis of the reachability set of the timed Petri net, it is possible to determine the possibility of system deadlock, automatically locate and prevent improper concurrent accesses to shared data, and develop minimum and maximum time bounds for processes in the CIM system.< >
暂无评论