P. C. Jha

OPTIMAL COMPONENT SELECTION OF COTS BASED SOFTWARE SYSTEM UNDER CONSENSUS RECOVERY BLOCK SCHEME INCORPORATING EXECUTION TIME

Computer based systems have increased dramatically in scope, complexity, pervasiveness. Most industries are highly dependent on computers for their basic day to day functioning. Safe & reliable software operations are an essential requirement for many systems across different industries. The number of functions to be included in a software system is decided during the software development. Any software system must be constructed in such a way that execution can resume even after the occurrence of failure with minimal loss of data and time. Such software systems which can continue execution even in presence of faults are called fault tolerant software. When failure occurs one of the redundant software modules get executed and prevent system failure. The fault tolerant software systems are usually developed by integrating COTS (commercial off-the-shelf) software components. The motivation for using COTS components is that they will reduce overall system development costs and reduce development time. In this paper, reliability models for fault tolerant consensus recovery blocks are analyzed. In first optimization model, we formulate joint optimization problem in which reliability maximization of software system and execution time minimization for each function of software system are considered under budgetary constraint. In the second model the issue of compatibility among alternatives available for different modules, is discussed. Numerical illustrations are provided to demonstrate the developed models.

Optimal Component Selection Problem for Cots Based Software System under Consensus Recovery Block Scheme: A Goal Programming Approach

Cost, reliability and time are the three main quality attributes of a software system. Now days much software are designed on COTS component in order to facilitate timely development with reduced cost and improved reliability. Software deigned to handle critical control systems have very high reliability requirements. Fault tolerance is designed in these systems for some or all of the software modules so that execution can be resumed even after failure with minimal loss of data and time. Designing fault tolerance requires extra resources. Even though reliability requirement are very high the developers can’t spend endless resources on any project. This is a trade off problem between reliability and cost. Many such problems have been discussed in literature considering distinct objectives and constraints and have given good results. An effective approach to discuss this problem is to formulate a multi-objective problem with cost minimization and reliability maximization as the two objectives with an upper bound on cost and lower bound on reliability. In this paper we formulate this bi-criteria problem and discuss the solution methodology. The problem is formulated for consensus recovery block fault tolerant scheme. In case a feasible solution for the problem exists, criterion vector approach is used to solve the problem and otherwise if the bounds are contradictory a goal programming approach is used to solve the problem to obtain a compromised solution. Alternative goal solutions are obtained assigning different weights for the objective to facilitate the decision maker with correct decision.

Fuzzy optimization approach to component selection of fault-tolerant software system

In developing software systems, a manager’s goal is to design software using limited resources and meet the user requirements. One of the important user requirements concerns the reliability of the software. The decision to choose the right software modules (components) becomes extremely difficult because of the number of parameters to be considered while making the decision. If suitable components are not available, then the decision process is further complicated with build versus buy decisions. In this paper, we have formulated a fuzzy multi-objective approach to optimal decision “build-or-buy” for component selection for a fault-tolerant modular software system under the consensus recovery block scheme. A joint optimization model is formulated where the two objectives are maximization of system reliability and minimization of the system cost with a constraint on delivery time. An example of developing a retail system for small-and-medium-size enterprises is used to illustrate the proposed methodology.

OPTIMAL COMPONENT SELECTION APPROACH FOR FAULT-TOLERANT SOFTWARE SYSTEM UNDER CRB INCORPORATING BUILD-OR-BUY DECISION

Application Package Software (APS) has emerged as a ready-to-use solution for the software industry. The software system comprises of a number of components which can be either purchased from the vendor in the form of COTS (Commercial Off-the-Shelf) or can be built in-house. Such a decision is known as Build-or-Buy decision. Under the situations wherein the software has the responsibility of supervising life-critical systems, the inception of errors in software due to inadequate or incomplete testing, is not acceptable. Such life-critical systems enforces upon meeting the quality standards of the software as unforbiddenable. This can be achieved by incorporating a fault-tolerant design that enables a system to continue its intended operation rather than failing completely when some part of the system fails. Moreover, while designing a fault-tolerant system, it must be apprehended that 100% fault tolerance can never be achieved and the closer we try to get to 100%, the more costly the system will be. The proposed model shall incorporate consensus recovery block scheme of fault tolerant techniques. Through this paper, we shall focus on build-or-buy decision for an APS in order to facilitate optimal component selection thereby, maximizing the reliability and minimizing the overall cost and source lines of code of the entire system. Further, since the proposed problem has incompleteness and unreliability of input information such as execution time and cost, hence, the environment in the proposed model is taken as fuzzy.

Optimal COTS selection for fault tolerant software system with mandatory redundancy in critical modules using consensus recovery block scheme under fuzzy environment

The dependence of mankind on software systems has made it necessary to produce highly reliable software. Software reliability is the major dynamic attribute of the software quality. Hence, it is essential to ensure software reliability for software products. The computer revolution has benefited society and increased the global productivity, but a major threat of this revolution is that the world has become critically dependent on the computing systems for proper functioning and timing of all its activities. While designing software it becomes very important to identify the critical modules in a software system. A system can be made fault tolerant by adding redundant components. Adding redundancy in critical modules may increase the reliability of the system and hence prevents system failure. So this paper aims at optimal selection of COTS components by minimizing the absolute deviational execution time by simultaneously maximizing the system reliability with a constraint on criticality of modules under fuzzy environment.

Testing-Coverage and Testing-Domain Models

Software development is a very complex and dynamic process. Every phase of software development can be further divided into a number of sub-phases, where each sub-phase has its own contribution to the software development process. Lot many activities are involved in each phase/sub-phase. Detailed study of each activity of this development process requires building an understanding of the various associated philosophies, theories and concepts. Same is true for the software testing phase and quality measurement.

Artificial Neural Networks Based SRGM

An Artificial Neural Network (ANN) is a computational paradigm that is inspired by the behavior of biological nervous systems, such as the brain, to process information. The key element of this paradigm is the novel structure of the information processing system. It is composed of a large number of highly interconnected processing elements (neurons) working in unison to solve specific problems capable of revealing complex global behavior, determined by the connections between the processing elements and element parameters. ANN, like people, learns by example. An ANN is configured for a specific application, such as pattern recognition or data classification, through a learning process. In more practical terms neural networks are non-linear statistical data modeling or decision-making tools. Learning in biological systems involves adjustments to the synaptic connections that exist between the neurons. This is true of ANN as well.

Formulation and characterization of lutetium-177-labeled stannous (tin) colloid for radiosynovectomy

Objective Easy large-scale production, easy availability, cost-effectiveness, long half-life, and favorable radiation characteristics have made lutetium-177 (177Lu) a preferred radionuclide for use in therapy. Lutetium-177-labeled stannous (177Lu-Sn) colloid particles were formulated for application in radiosynovectomy, followed by in-vitro and in-vivo characterization. Methods Stannous chloride (SnCl2) solution and 177Lu were heated together, the pH was adjusted, and the particles were recovered by centrifugation. The heating time and amount of SnCl2 were varied to optimize the labeling protocol. The labeling efficiency (LE) and radiochemical purity (RCP) of the product were determined. The size and shape of the particles were determined by means of electron microscopy. In-vitro stability was tested in PBS and synovial fluid, and in-vivo stability was tested in humans. Results LE and RCP were greater than 95% and ∼99% (Rf=0–0.1), respectively. Aggregated colloidal particles were spherical (mean size: 241±47 nm). The product was stable in vitro for up to 7 days in PBS as well as in synovial fluid. Injection of the product into the infected knee joint of a patient resulted in its homogenous distribution in the intra-articular space, as seen on the scan. No leakage of activity was seen outside the knee joint even 7 days after injection, indicating good tracer binding and in-vivo stability. Conclusion 177Lu-Sn colloid was successfully prepared with a high LE (>95%) and high RCP (99%) under optimized reaction conditions. Because of the numerous benefits of 177Lu and the ease of preparation of tin colloid particles, 177Lu-Sn colloid particles are significantly superior to its currently available counterparts for use in radiosynovectomy.

Unification of SRGM

We are aware that it is the computer systems on which the entire modern information society rolls over. Computer hardware systems have attained high productivity, quality and reliability but it is still not true for the software systems. Software engineers and concerned managements put more labor for improving these characteristics of software nowadays. Unlike hardware components, every new software must be tested even though various techniques are employed throughout the software development process to satisfy software quality requirements. The achieved quality level through testing has no meaning unless it is measured quantitatively to build a confidence in the level of reliability achieved. Besides this many decisions such as release time, those related to the postrelease can be made more accurately only if a quantitative measurement of quality is known.

Imperfect Debugging/Testing Efficiency Software Reliability Growth Models

Software systems are the means developed and designed by humans for automated operation of several types of real operating systems meant for human kind. Even though the creator of software systems is the universe most dominant and intelligent creature in the universe we cannot deny the possibility of software failures during their operation period. These failures are mainly due to faults manifested in them by their designers. Primarily testing of software is performed with a goal to detect and remove most of the underlying faults. Even though the software testing and debugging team put its best efforts, uses distinct methods and techniques or the developers makes heavy expenditure on testing and debugging latest, well planed and controlled strategies, we cannot be sure that the software can be made free of all type of faults at the time of its launch.