Browsing by Author "Liang, DR"

Now showing 1 - 4 of 4

A fault-tolerant object service on CORBA
(1997)
Sheu, GW
;
Chang, YS
;
Liang, DR
;
Yuan, SM
;
Lo, W
There are more and more COSS (Common Object Service Specification) on CORBA (Common Object Request Broker Architecture) that is announced by the OMG (Object Management Group), bur no common specification about fault-tolerance exists now. In this paper, we propose a ''warm stand-by'' replication approach. When an object (primary object) is invoked, it will invoke a secondary object, and the primary object will log the messages and checkpoint the state to the secondary object periodically. If the primary object fails, the secondary object can take over by way of client executing a few operations to change secondary object's mode to primary's. Following the style of COSS, we define four interfaces and provide class implementations that can help programmers write programs with fault-tolerant capability. The whole model has been implemented on Orbix, which is a full implementation of CORBA specification.
Design and implementation of multi-threaded object request broker
(1998)
Chang, YS
;
Lo, W
;
Wang, CJ
;
Yuan, SM
;
Liang, DR
Distributed object-oriented computing model is the next logical step to develop distributed applications. In recent year, several object models have been proposed, such as COM/DCOM, CORBA, and JAVA Bean etc. In CORBA, which is announced by OMG, object request broker is a software bus to connect applications and object components. In addition, multi-threaded programming is a well-known technique to improve the performance of applications. In CORBA environment, clients can invoke the remote objects that are shared. If those objects are single-threaded it will affect the performance of system by the large distributed applications. In this paper we will depict in detail the design and implementation of multi-threaded object request broker based on the CORBA. Our ORE nas implemented atop Windows NT and underlying TCP protocol. Finally, we will compare our system's performance with IONA's Orbix, which is a well-known commercial product, in both one-way and two-way request.
Reliability analysis of replicated and-or graphs
(1997-07-01)
Liang, DR
;
Jan, RH
;
Tripathi, SK
;
資訊工程學系
;
Department of Computer Science
A computation task running in distributed systems can be represented as a directed graph H(V, E) whose vertices and edges may fail with known probabilities. In this paper, we introduce a reliability measure, called the distributed task reliability, to model the reliability of such computation tasks. The distributed task reliability is defined as the probability that the task can be successfully executed. Due to the and-fork/and-join constraint, the traditional network reliability problem is a special case of the distributed task reliability problem, where the former is known to be NP-hard in general graphs. For two-terminal and-or series-parallel (AOSP) graphs, the distributed task reliability can be computed in polynomial time. We consider a graph H-k((V) over cap, (E) over cap, named a k-replicated and-or series-parallel (RAOSP) graph, which is obtained from an AOSP graph H(V, E) by adding (k - 1) replications to each vertex and adding proper edges between two vertices. It can be shown that the RAOSP graphs are not AOSP graphs; thus, the existing polynomial algorithm does not apply. Previously, only exponential time algorithms as used in general graphs are known for computing the reliability of H-k((V) over cap, (E) over cap. In this paper, we present a linear time algorithm with O(K(V + E)) complexity to evaluate the reliability of the graph H-k((V) over cap, (E) over cap), where K = max{k(2)2(2k), 2(3k)}. (C) 1997 John Wiley & Sons, Inc.
Reliability analysis of replicated and-or graphs
(1997-07-01)
Liang, DR
;
Jan, RH
;
Tripathi, SK
;
資訊工程學系
;
Department of Computer Science
A computation task running in distributed systems can be represented as a directed graph H(V, E) whose vertices and edges may fail with known probabilities. In this paper, we introduce a reliability measure, called the distributed task reliability, to model the reliability of such computation tasks. The distributed task reliability is defined as the probability that the task can be successfully executed. Due to the and-fork/and-join constraint, the traditional network reliability problem is a special case of the distributed task reliability problem, where the former is known to be NP-hard in general graphs. For two-terminal and-or series-parallel (AOSP) graphs, the distributed task reliability can be computed in polynomial time. We consider a graph H-k((V) over cap, (E) over cap, named a k-replicated and-or series-parallel (RAOSP) graph, which is obtained from an AOSP graph H(V, E) by adding (k - 1) replications to each vertex and adding proper edges between two vertices. It can be shown that the RAOSP graphs are not AOSP graphs; thus, the existing polynomial algorithm does not apply. Previously, only exponential time algorithms as used in general graphs are known for computing the reliability of H-k((V) over cap, (E) over cap. In this paper, we present a linear time algorithm with O(K(\V\ + \E\)) complexity to evaluate the reliability of the graph H-k((V) over cap, (E) over cap), where K = max{k(2)2(2k), 2(3k)}. (C) 1997 John Wiley & Sons, Inc.