bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions between mosses (Bryophyta) and fungi
Authors: Davey Marie L. , Currah Randolph S. 
Published: January 2007

A taxonomically diverse suite of fungi interacts with bryophytes as pathogens, parasites, saprobes, and commensals. Necrotrophic pathogens such as Tephrocybe palustris (Peck) Donk and Nectria mnii Döbbeler form patches of moribund gametophytes in otherwise healthy mats of mosses. These pathogens exhibit different methods of host cell disruption; N. mnii appears to displace the host cell protoplast with intracellular hyphae, while T. palustris causes host protoplast degeneration. Host responses to infection by bryopathogens are also variable. Host–pathogen relationships can be highly evolved, as in Bryophytomyces sphagni (Navashin) Cif., in which fungal propagules replace the bryophyte spores, and exploit the explosive dispersal mechanisms of the Sphagnum host. Bryophilous parasites tend to exhibit high tissue or cellular specificity with varying host specificity. For example, Octospora similis (Kirchstein) Benkert infects the rhizoids of species of Bryum, and Discinella schimperi (Navashin) Redhead specifically colonizes the mucilage producing cells of stems of Sphagnum squarrosum Crome. Eocronartium muscicola (Pers.) Fitzp. demonstrates a highly evolved host–parasite relationship in which the basidiocarp displaces the sporophyte and is fed directly by the gametophyte through specialized transfer tissues. Fungi such as Oidiodendron maius Barron are capable of decomposing moss cell walls that are generally resistant to decomposition because of their polyphenolic component. Mycorrhizal fungi, including Glomus, Suillus, and Endogone, have not been observed to form functional, nutrient-exchanging mycorrhizal interfaces with bryophytes, rather, they function as saprobes on moribund and senescent gametophytes. Finally, endophytic fungi may provide bryophyte hosts with greater tolerance to extreme pH or promote vegetative growth. In vivo observation of bryophyte–fungus interactions has provided insight into the types of interactions that occur; however to further understand the physiology, anatomy, and etiology of these interactions, it is necessary to culture bryophilous fungi in vitro and create artificial axenic systems for study.
A manufacturing capacity planning experiment through functional workload decomposition
Authors: Lee T. P. 
Published: January 2007

In this paper, we describe an experiment to evaluate a distributed architecture via functional database workload decomposition. A workload in a circuit pack assembly environment was decomposed and mapped onto a frontend/backend distributed computer architecture. To evaluate this distributed architecture, an operational model for capacity planning was devised, and performance and cost-effectiveness measures were chosen. Model parameters were estimated through benchmark experiments in a distributed system consisting of various super-microcomputers connected by a CSMA/CD local area network with INGRES as the database management system.
The frontend/backend architecture consists of a backend data repository and analysis computer system and a few frontend computer systems dedicated for data collection and manufacturing process verification. Because of the significant software overhead in communication protocol and database processing, information exchange was batched between the backend and frontend systems to amortize such cost to improve overall system performance.
Results of the experiments were analyzed to gain quantitative insight on the feasibility of such decomposition and its mapping onto the proposed architecture. With sufficient batching, the proposed distributed architecture not only has more overall system capacity, but also is more cost-effective than the typical centralized architecture. The approach described is applicable in more general contexts. Advantages of such distributed systems include the relative robustness of the distributed architecture under single point failure mode and the ease of capacity growth by upgrading the computer systems and/or by increasing the number of frontend systems.
The analysis of storage constraints by a queueing network model with blocking
Authors: Reiser M. , Konheim A. G. 
Published: January 2007

The finite capacity of storage has a significant effect on the performance of a contemporary computer system. Yet it is difficult to formulate this problem and analyze it by existing queueing network models.
We present an analysis of an open queueing model with two servers in series in which the second server has finite storage capacity.

This network is an exponential service system; the arrival of requests into the system is modeled by a Poisson process (of rate λ) and service times in each stage are exponentially distributed (with rates α and β respectively). Requests are served in each stage according to the order of their arrival. The principal characteristic of the service in this network is
blocking
; when M requests are queued or in service in the second stage, the server in the first stage is blocked and ceases to offer service. Service resumes in the first stage when the queue length in the second stage falls to M-1. Neuts [1] has studied two-stage blocking networks (without feedback) under more general statistical hypothesis than ours. Our goal is to provide an algorithmic solution which may be more accessible to engineers.
Statistical validation of a trace-driven simulator
Authors: Schatzoff M. , Tillman C. C. 
Published: January 2007

A common problem encountered in computer system simulation is that of validating that the simulator can produce, with a reasonable degree of accuracy, the same information that can be obtained from the modelled system. This is basically a statistical problem because there are usually limitations with respect to the number of controlled tests which can be carried out, and assessment of the fidelity of the model is a function of the signal to noise ratio. That is, the magnitude of error which can be tolerated depends upon the size of the effect to be predicted.
In this paper, we describe by example how techniques of statistical design and analysis of experiments have been used to validate the modeling of the dispatching algorithm of a time sharing system. The examples are based on a detailed, trace-driven simulator of CP-67. They show that identical factorial experiments involving parameters of this algorithm, when carried out on both the simulator and on the actual system, produced statistically comparable effects.
Adaptive optimization of the performance of a virtual memory computer
Authors: Badel M. , Gelenbe E. , Leroudier J. , Potier D. , Lenfant J. 
Published: January 2007

It is known that the regulation of the degree of multiprogramming is perhaps one of the most important factors determining the overall performance of a virtual memory computer. In this paper we present an approach which differs some what from the approaches usually taken to regulate the degree of multiprogramming, which are mainly derived from the working-set principles.
We design a controller which will regulate the system in order to optimize a given performance measure. The controller is applied to a system where the critical resource is primary memory, and we are only concerned with systems where ineffective regulation leads to the phenomenon known as thrashing due to extensive paging activity.
In the first section, the dynamics of the system we wish to regulate are investigated using an analytical model. The system consists of a set of terminals and of a resource loop (CPU, secondary memory device, file disk) shared by the users. Using classical assumptions about program behavior (e.g., life-time function), the throughput of the RL is obtained as a function of the degree of multiprogramming n (number of users sharing the resources at a given instant of time) and of the system parameters. This result provides a greater insight of the “plant” we wish to control. The mathematical results are validated and extended with data from simulation experiments using a more detailed model (overheads and non-exponential assumption).

In the next section, a criterion called “dilatation” based on the utilization of the different resources is defined. From the analytical and simulation results of the first section, it can be shown that there exists a value n
o
of the degree of multiprogramming which maximizes this criterion. The regulation of n to n
o
is achieved by controlling the access of the users to the RL. The value of n
o
is estimated in real-time through a continuous estimation of the two first moments of the criterion. Using these estimations, the decision of introducing or not a new user in the RL is taken whenever a user leaves a terminal or departs from the RL.

Extensive simulation experiments were conducted, where the implementation of the different functions of the controller have been thoroughly simulated. They have shown that the control scheme leaves to an improvement of the system performance in mean response time and resource utilization, and, overall, adapts in real-time the degree of multiprogramming to the characteristics of the users (the adaptation is performed in 4 sec. or so for a unit variation of the optimal degree of multiprogramming). A discussion of practical application of results ends the paper.
Requirements language processing for the effective testing of real-time systems
Authors: Davis Alan M. , Rataj Walter J. 
Published: January 2007

GTE Laboratories is currently developing a trio of software tools which automate the feature testing of real-time systems by generating test plans directly from requirements specifications. Use of the first of these tools, the Requirements Language Processor (RLP), guarantees that the requirements are complete, consistent, non-ambiguous, and non-redundant. It generates a mode] of an extended finite-state machine which is used by the second tool, the Test Plan Generator, to generate test plans which thoroughly test the software for conformity to the requirements. These test plans are supplied to the third tool, the Automatic Test Executor, for actual testing. The RLP is the subject of this paper.
The primary goal of the RLP is to provide the ability to specify the features of a target real-time system in a vocabulary familiar to an application-oriented individual and in a manner suitable for test plan generation. The RLP produces a document which can be easily understood by non-computer personnel. It is expected that this document will function as a key part of the “contract” between a real-time system supplier and a customer. This document must also serve as a springboard for the software designers during their development of the actual product.
In addition to the requirements document, the RLP also produces an augmented state transition table which describes a finite state machine whose external behavior is identical to the target real-time system as defined by the specified requirements.
Nassi-Shneiderman charts an alternative to flowcharts for design
Authors: Yoder Cornelia M. , Schrag Marilyn L. 
Published: January 2007

In recent years structured programming has emerged as an advanced programming technology. During this time, many tools have been developed for facilitating the programmer's use of structured programming. One of these tools, the Structured Flowcharts developed by I. Nassi and B. Shneiderman in 1972, is proving its value in both the design phase and the coding phase of program development.
Several programming groups in System Products Division, Endicott, New York, have used the Nassi-Shneiderman charts as replacements for conventional flowcharts in structuring programs. The charts have been used extensively on some projects for structured walk-throughs, design reviews, and education.
This paper describes the Nassi-Shneiderman charts and provides explanations of their use in programming, in development process control, in walk-throughs, and in testing. It includes an analysis of the value of Nassi-Shneiderman charts compared to other design and documentation methods such as pseudo-code, HIPO charts, prose, and flowcharts, as well as the authors' experiences in using the Nassi-Shneiderman charts.
The paper is intended for a general data processing audience and although no special knowledge is required, familiarity with structured programming concepts would be helpful. The reader should gain insight into the use of Nassi-Shneiderman charts as part of the total development process.
IDBUG
Authors: Drasch Frederick J. , Bowen Richard A. 
Published: January 2007

The construction of a reliable computer program requires, in part, a means of verification of its component parts prior to their integration into the overall system. The verification process may consist of building a test harness to exercise or exhaustively test a procedure. This technique is known as dynamic testing. In practice, the application of dynamic testing requires the coding of a special harness for each procedure. This consumes valuable programming time, as much as 50% of the total effort (FAIR78). It is also restrictive because the test harness cannot be easily modified to test aspects of a program which it was not originally designed to test.
We have built a facility called IDBUG that reduces the programming effort required to employ dynamic testing by automating the construction of the test harness. Additionally, it provides an interactive test environment which permits more flexible testing. This paper describes IDBUG and discusses our experience in its application to maintenance tasks in a commercial environment. Nyone of the ideas put forth here will be especially novel; dynamic testing as a software testing tool has been in use for some time. What we hope to do is illustrate the beneficial aspects of a particular application of dynamic testing. It is argued that testing should play a more limited role in assuring the reliability of software in light of techniques such as structured coding, top-down design, proof of correctness, etc. (McG075). While it is true that eventually the “art of computer programming” will become the “science of producing correct programs”, we believe that more emphasis must be placed on interim solutions to aid in the construction of reliable software. We present IDBUG as such a solution.
An application of graph theory to software test data selection
Authors: Stickney M. E. 
Published: January 2007

Graph theory is playing an increasingly important role in the design, analysis, and testing of computer programs. It's importance is derived from the fact that flow of control and flow of data for any program can be expressed in terms of directed graphs. From the graph representing the flow of control, called the program graph, many others can be derived that either partially or completely preserve the program control structure. One derived graph known as a cyclomatic tree is of particular value in program testing. It is so named because the number of leaves of the tree is equal to the cyclomatic number of the program graph. A thorough treatment of cyclomatic numbers is provided in [3]. A program called the Complexity/Path Analyzer (CPA) has been developed that builds and utilizes a program cyclomatic tree to provide test planning information, automatically place software counters called probes as discussed in [9] and [10] in a program, and provide selected parameters such as program length and program graph cyclomatic number. The paper discusses the features and derivation of cyclomatic trees as well as their value and application to testing and test data generation.
A cyclomatic tree provides a test planner with information useful for planning program tests. In particular, it furnishes test data selection criteria for developing tests that are minimally thorough as defined by Huang in [9]. A test data selection criterion will be defined as minimally thorough if any complete test with respect to the criterion is at least minimally thorough. The term complete is used as defined by Goodenhough and Gerhart in [13]. A test is defined to be a non empty sequence of test cases. Each test case consists of an element selected from the input domain of the program being tested. The paper discusses the merits of one particular technique selected to achieve a minimally thorough test data selection criteria. Part of the technique is automated by the CPA program.
Software quality assurance tools
Authors: Fischer Kurt F. 
Published: January 2007

The objective of software quality assurance (QA) is to assure sufficient planning, reporting, and control to affect the development of software products which meet their contractual requirements. To implement this objective, eight QA functions can be identified:
1. Initial quality planning
2. Development of software standards and procedures
3. Development of quality assurance tools
4. Conduct of audits and reviews
5. Inspection and surveillance of formal tests
6. Configuration verifications
7. Management of the discrepancy reporting system
8. Retention of QA records
The purpose of this paper is to document experiences gained in the use of selected QA tools that perform some of the above functions, to discuss lessons learned, and to suggest future needs.
The evolution of a Source Code Control System
Authors: Glasser Alan L. 
Published: January 2007

The Source Code Control System (SCCS) is a system for controlling changes to files of text (typically, the source code and documentation of software systems). It is an integral part of a software development and maintenance system known as the Programmer's Workbench (PWB).
SCCS has itself undergone considerable change. There have been nine major versions of SCCS. This paper describes the facilities provided by SCCS, and the design changes that were made to SCCS in order to provide a useful and flexible environment in which to conduct the programming process.
A quantitative evaluation of the effectiveness of quality assurance as experienced on a large-scale software development effort
Authors: Belford Peter Chase , Broglio Carlo 
Published: January 2007

The purpose of quality assurance on software projects is to achieve high quality products on schedule, within cost, and in compliance with contract requirements. However, historically, the effectiveness of these activities on software projects has not been quantitatively demonstrable because of a lack of data collected on the project combined with a lack of insight into the operational reliability of the system.
Quality assurance is a collection of activities on a contractual deliverable whose purpose is to impart a degree of confidence that the deliverable will conform to the customer's concept of what was procured. Under these conditions, quality assurance must be performed with respect to a documented baseline of the concept. This baseline can address the need in the form of requirement statements; the conceptual approach to be followed in the form of a functional specification; or the design to be implemented in the form of a design specification. Further, these baselines are hierarchical in the sense that when quality assurance is applied to a level it is implicitly applied to all lower levels; e.g., if the need is to be satisfied, the conceptual approach must be satisfied. Effective quality assurance programs impart a high degree of confidence to the customer without significant impacts on schedule or cost. Historically, this effectiveness has not been quantitatively demonstrable because of a lack of data collected on the project combined with a lack of insight into the operational reliability of the system.
An example of software quality assurance techniques used in a successful large scale software development
Authors: Kacik Paul J. 
Published: January 2007

Development of the software package for the Combat Grande Air Defense System was considered by the Hughes Aircraft Company to be highly successful in that a reliable system was produced that met customer requirements and was completed within time and budget allocations - a feat not often attained in large scale software developments. Much of the success can be attributed to the software quality assurance (QA) techniques used. Some of these QA techniques are listed in Table 1 along with the phases in which they were used.
This paper describes these QA techniques in some detail, as well as those aspects of the system and software development program that permitted these techniques to be used effectively.
Background information is presented first which describes the system, software, organization and software configuration management. This is followed by a description of the three major phases of software development. The overall results are then presented, followed by recommended improvements and conclusions. Many of the QA techniques listed in Table 1 were used in several phases of software development. However, a particular technique is discussed only in the phase in which it was most extensively used.
The lazy repairman and other models
Authors: Shore John E. 
Published: January 2007

We consider two simple models of overhead in batch computer systems and demand access communications systems. The first, termed “modified M/M/1/K, ” is an exponential, single-server queuing system with finite storage capacity, constant arrival rate, and queue-length-dependent service time. We consider cases in which the expected service time consists of a constant plus a term that grows linearly or logarithmically with the queue length. We show that the performance of this system—as characterized by the expected number of customers in the system, the expected time in the system, and the rate of missed customers—can collapse as the result of small changes in the arrival rate, the overhead rate, or the queue capacity. The system has the interesting property that increasing the queue capacity can decrease performance. In addition to equilibrium results, we consider the dynamic behavior of the model. We show that the system tends to operate in either of two quasi-stable modes of operation—one with low queue lengths and one with high queue lengths. System behavior is characterized by long periods of operation in both modes with abrupt transitions between them. We point out that the performance of a saturated system may be improved by dynamic operating procedures that return the system to the low mode.
In the second model, termed the “lazy repairman, ” the single server has two distinct states: the “busy” state and the “lazy” state. Customers receive service only when the server is in the busy state; overhead is modeled by attributing time spent in the lazy state to overhead functions. When the expected time spent in the lazy state increases with the number of customers waiting for service, the behavior of the lazy repairman model is similar to the modified M/M/1/K, although the lazy repairman model makes it easier to study in detail the effects of overhead.
The response of job classes with distinct policy functions(Extended Abstract)
Authors: Ruschitzka Manfred 
Published: January 2007

Policy function schedulers provide a flexible framework for implementing a wide range of different scheduling schemes. In such schedulers, the priority of a job at any instant in time is defined by the difference between the time it spent in the system and an arbitrary function of its attained service time. The latter is called the policy function and acts as the functional parameter that specifies a particular scheduling scheme. For instance, a constant policy function specifies the first-come, first-serve scheduling scheme. By changing the policy function, the system behavior can be adjusted to better conform with desired response characteristics. It is common to express response characteristics in terms of a response function, the average response time of a job conditioned on its service requirement in equilibrium.
In this paper, we analyze processor-sharing M/G/1 systems in which the priorities of different classes of jobs are determined by distinct policy functions.