Philip J. Bernhard

A reduced test suite for protocol conformance testing

Let M be a finite-state machine, and let S be an implementation of M. The protocol-testing problem is the problem of determining if S is a correct implementation of M. One known method for solving this problem, called the W-method, has the disadvantage that it generates a relatively large test set. In this paper, we describe three new versions of this method. We prove that these versions all have the same fault detection capability as the W-method. In addition, we show that in most cases all three generate a smaller number of tests than the W-method. Specifically, suppose Ml and Mz are finite-state machines having n and m states, respectively, where Ml is a specification (M), Mz is an implementation (S), and m > n. In addition, suppose they have input alphabet X, where 1X1= k; let a be the total number of strings in a characterization set for Ml, and let ~ be the total number of strings in a transition couer set for Ml. The W-method will generate a test set consisting of afl(k M n+ 1 – I)/(k – 1) strings. In contrast, our first algorithm will generate a test set containing at most B( a + km-n ) strings. For our second algorithm, the number of strings will be ~kmaxt’l>m-”j, and for the third, ~(kn 1 + km-”), When m >> ~, all three of our algorithms will produce fewer strings than the W-method. Finally, two of our algorithms make use of a heuristic for minimizing the number of strings in a characterization set. We show that the performance ratio for this heuristic has an upper bound of O(log n).

Efficient sets in graphs

Abstract The efficiency of a set S of vertices in an undirected graph G =( V , E ) is defined to be e ( S )=|{ v | vϵV — S and v is adjacent to exactly one vertex in S }|, i.e., the number of vertices in V—S that are dominated by exactly one vertex in S . The efficiency of a graph G =( V , E ) equals the maximum efficiency of any subset S of vertices of V . A linear time algorithm is presented for computing the efficiency of an arbitrary tree and an NP-completeness proof is given for the problem of deciding if an arbitrary planar bipartite graph has a set S such that e ( S )≥ k , for some positive integer k .

An efficient method for representing and transmitting message patterns on multiprocessor interconnection networks

We describe a formalism for representing address sets, and for representing message patterns for multiprocessor interconnection networks. In this formalism a descriptor called a mask is used to represent a set of equal length bit vectors. Such a set can be interpreted as a set of processor addresses, or as a set of messages. We focus on the implications that this formalism has for routing message patterns on bundled omega networks. Specifically, we show that when a message pattern is represented in this formalism, a number of properties of the message pattern can be determined in polynomial time. This includes such things as determining whether the message pattern contains congestion. In addition, we show that the formalism defines a subclass of message patterns for which the minimum round partitioning problem, which in general is NP-hard, is solvable in linear time. We show this result to be true for both broadcast and non-broadcast bundled omega networks. This generalizes a known result for bit-permute-complement permutations to a more general class of message patterns, and to a larger class of networks.

Using the dual path property of omega networks to obtain conflict-free message routing

A strategy for dealing with communication conflicts that occur in omega networks is presented. The strategy operates by implementing the dual path property of omega networks, which allows the source and destination processors to reverse roles for some of the messages that are being transmitted. For certain message patterns, such a reversal produces a modified message pattern for which the network routes are disjoint. For a circuit switching mode in which the network links and switches are bidirectional, the disjoint set of routes for modified message pattern can be used to achieve conflict-free message transmission for the original message pattern. This strategy is investigated, and an efficient algorithm to determine whether it can be successfully applied to a given message pattern is presented. >

Partitioning message patterns for bundled omega networks

Considers a strategy for dealing with communication conflicts in omega networks. Specifically, the authors consider the problem of partitioning a set of conflicting messages into a minimum number of subsets, called rounds, each free of communication conflicts. In addition to standard omega networks, they consider this problem for a more general class of networks called bundled omega networks, where interconnection links in the network are replaced by bundles of wires. Although the partitioning problem has previously been considered in the literature, its computational complexity has remained open. The authors show that for a number of cases, the problem is NP-complete, but for certain special cases, it is solvable in polynomial time. In addition, they present a class of distributed, on-line heuristics for the problem. Finally, they give a lower bound of /spl Omega/(log N) on the performance ratio for one of these heuristics. >

Industrial evaluation of a highly-accurate academic IR system

In this paper we report the results of an independent experimental evaluation of an information retrieval (IR) system developed at the Illinois Institute of Technology (IIT). The system, which is called the Advanced Information Retrieval Engine (AIRE), consists of a set of tools and utilities providing indexing, extraction, searching and visualization. We evaluated AIRE on three data sets from the Text REtrieval Conference (TREC) - TREC 8, 9 and 10. Overall, our results indicate that AIRE is a highly accurate IR system. Compared with results published by IIT, in our experiments AIRE consistently scored higher in recall. AIRE also scored higher in precision, but only for automatic tasks. In manual tasks, AIRE scored lower in precision in our experiments, but we attributed that to factors external to AIRE. Our final conclusion is that AIRE is a highly accurate IR system.

XML strategies for legacy database search

Over the past few years, XML (Extensible Markup Language) has become the standard for data and document interchange between distributed systems. With the continuing proliferation of the Internet, XML has also become a key technology for transactional e-business. A large percentage of Internet interactions, however, involves searching through documents, Web pages, databases, and other information resources. This article explores some of the ways XML can improve these types of searches. It focuses particularly on searches through legacy databases and on the changes you can make to your legacy systems to effectively exploit XML.

Bounds on the performance of message routing heuristics

Let S be a set of messages to be routed on an N*N omega network. In addition, suppose that S contains communication conflicts. One strategy to deal with such conflicts is to partition S into some number of subsets, called rounds, such that each subset is conflict-free. The messages are then routed through the network by successively routing the messages in each subset. The minimum round partitioning problem is the problem of partitioning a given message set into a minimum number of rounds. The author establishes upper and lower bounds on the performance ratio for two heuristics for partitioning message patterns into rounds. For both of these heuristics they give upper and lower bounds of O (log N) and Omega (logN), respectively. >

Bounds on the performances of message routing heuristics

Let S be a set of messages to be routed on an N*N omega network. In addition, suppose that S contains communication conflicts. One strategy to deal with such conflicts is to partition S into some number of subsets, called rounds, such that each subset is conflict-free. The messages are then routed through the network by successively routing the messages in each subset. The minimum round partitioning problem, is the problem of partitioning a given message set into a minimum number of rounds. The authors consider heuristics for the minimum round partitioning problem. In particular, they establish upper and lower bounds on the performance ratio for two heuristics. For the first heuristic they give upper and lower bounds of O( square root N) and Omega (logN), respectively. For the second heuristic they give a lower bound of Omega (logN), which matches a known upper bound of O(logN).<<ETX>>

Modeling and simulation of explosion effectiveness as a function of blast and crowd characteristics

Explosions in civil settings are becoming the daily news. While various explosive simulations and models have been developed for battlefield and industrial settings, much less has been done for civil settings and urban terrains.This paper presents the science of suicide bombing and explains the physics, explosive models, mathematics, and the assumptions we need to create such a simulation.The proposed simulation tool is capable of assessing the impact of crowd formation patterns and their densities on the magnitude of injury and number of casualties during a suicide bombing attack. Results indicate that the worst crowd formation is a street (zigzag) where 30% of the crowd can be dead and 45% can be injured, given the typical explosive carrying capacity of a single suicide bomber. Row-wise crowd formation was found to be the best for reducing the effectiveness of an attack with 18% of the crowd in the lethal zone and 38% in the injury zone. Crowd blockage and densities can reduce the fatalities by 12% and injuries by 7%. Simulation results were compared and validated by real-life incidents and found to be in good agreement. These findings, although preliminary, may have implications for emergency response and counter terrorism.