A comprehensive approach to optimal software rejuvenation

Software aging is caused by resource exhaustion and can lead to progressive performance degradation or result in a crash. We develop experiments that simulate an on-line bookstore application, using the standard configuration of TPC-W benchmark. We study application failures due to memory leaks, using the accelerated life testing (ALT). ALT significantly reduces the time needed to estimate the time to failure at normal level. We then select the Weibull time to failure distribution at normal level, to be used in a semi-Markov model so as to optimize the software rejuvenation trigger interval. Then we derive the optimal rejuvenation schedule interval by fixed point iteration and by an alternative non-parametric estimation algorithm. Finally, we develop a simulation model using importance sampling (IS) to cross validate the ALT experimental results and the semi-Markov model, and also we apply the non-parametric method to cross validate the optimized trigger intervals by comparing the availabilities obtained from the semi-Markov model and those from IS simulation using the non-parametric method.     

双抗衰系统协同工作模型

"软件衰退"现象在软件系统中普遍存在,利用"软件抗衰"技术可以在软件出现衰退时提高系统性能,针对基于MIDAS三层架构系统结构的特殊性,提出一种双抗衰系统工作模型分布在中间层应用服务器和数据库服务器端协同工作,可以应对三层架构系统部分或整体出现衰退,采用应用级或系统级恢复,提高系统整体的性能,同时也保障了数据的完整性、安全性.     

A transient interval reliability analysis for software rejuvenation models with phase expansion

Software Quality Journal - The phenomenon of software aging refers to the continuing degradation of software system performance with the operation time and is usually caused by the aging-related...     

A survey on software aging and rejuvenation in the cloud

Software Quality Journal - The adoption of cloud computing for providing resource and delivering services is an irreversible trend. For most IT companies, the quality of provided services is...     

A model for software reuse

Software reusability is widely believed to be a key to help overcome the ongoing software crisis by improving software productivity and quality. New computer technology and the demands of an advancing society require new and more complicated software. It is unrealistic to expect that every software system can be developed solely reusing existing software; however, software reusability has proven to be a way of enhancing software productivity and quality in different organizations. It is also believed that reuse of code segments alone does not significantly reduce software development effort.By creating reuse support information while software is being developed (when the software is best known to software developers), the reuse effort for both software development and maintenance can be potentially reduced.In this paper, five types of RSI are presented: Semantic Web, Horizontal Web, Vertical Web, Syntactic Web, and Alternative Web. We collectively call these five webs a Quintet Web. The Semantic Web enables software developers to locate a software segment. The Horizontal Web provides a means to reuse a block of soflware along with other types of software from other phases of a development process. The inter-phase integration of software can be performed through this Web. The Vertical Web identifies the vertical relationship of a software block to its operational environment. The Syntactic Web locates all statements in which a variable is used. The Alternative Web provides alternative software blocks that perform an identical operation.A prototype of the Quintet Web is presented.     

Methods and opportunities for rejuvenation in aging distributed software systems

In this paper we describe several methods for detecting the need for software rejuvenation in mission critical systems that are subjected to worm infection, and introduce new software rejuvenation algorithms. We evaluate these algorithms’ effectiveness using both simulation studies and analytic modeling, by assessing the probability of mission success. The system under study emulates a Mobile Ad-Hoc Network (MANET) of processing nodes. Our analysis determined that some of our rejuvenation algorithms are quite effective in maintaining a high probability of mission success while the system is under explicit attack by a worm infection.     

A costing model for software conversions

In this paper a cost model for software conversion projects is developed. The model is based upon three variable parameters: L (thousands of lines of source code), N (the total number of programs being converted) and E (the conversion software inefficiency). All other parameters included in the model are constant coefficients which can vary from one type of conversion to another. An analysis of the resulting model yields four major conclusions: (1) There is an optimum investment that should be made in conversion software for each conversion project. (2) As the total number of lines to be converted increases, it is cost-effective to increase the investment in conversion software. (3) If conversion software is reused for a second project, it is worthwhile to invest additional effort (and/or funds) in upgrading the software. (4) As the size of the conversion increases the cost per line decreases to a lower limit.     

A graph model for software evolution

A graph model of software evolution is presented. The author seeks to formalize the objects and activities involved in software evolution in sufficient detail to enable automatic assistance for maintaining the consistency and integrity of an evolving software system. This includes automated support for propagating the consequences of a change to a software system. The evolution of large and complex software systems receives particular attention     

A model for software product quality

A model for software product quality is defined, it has been formulated by associating a set of quality-carrying properties with each of the structural forms that are used to define the statements and statement components of a programming language. These quality-carrying properties are in turn linked to the high-level quality attributes of the International Standard for Software Product Evaluation ISO-9126. The model supports building quality into software, definition of language-specific coding standards, systematically classifying quality defects, and the development of automated code auditors for detecting defects in software     

A generic model for software architectures

In other industries, the idea of build corporate culture by establishing a common level of “best practice” is widely known and used. The architecture concept directly supports this goal for our industry and can help us improve problem areas dominated by organizational and social issues, such as health care organizations, educational systems, and so on. Our proposed reference model for architecture specification and development is organized around a set of aspects that structure concepts and rules; these, in turn, specify a conceptual architecture. We have added principles and guidelines to the concepts and rules to give a more complete picture of the architecture and to provide a place to store and communicate successfully applied design patterns and other knowledge related to the architecture. Adding architectural elements is a step toward a more constructive type of architecture representation. Our current research is focused on further refining these concepts and developing a formal specification of the architecture reference model. We are continuing to test our ideas in case studies, such as applying our model to the OSCA architecture and the application machine concept. We are also developing a prototype architecture editor, and we are testing different tools to learn more about integrating them into a real infrastructure and to learn what typical services an infrastructure must provide     

A comprehensive program representation of object-oriented software

An extensible representation for object-oriented programs, the Object-oriented Program Dependence Graph (OPDG), is presented. The representation is divided into three layers: a first layer that presents the class inheritance structure, a second layer that combines a traditional control dependence subgraph and a data dependence subgraph with objects, and a third layer that presents the dynamic, runtime aspects of an object-oriented program as an Object Dependence Subgraph. The representation is modular allowing specific tools to only use the portion required for the tool's operation. The complete representation provides information sufficient for most program analysis techniques including data flow analysis, reverse engineering, interactive debuggers and other tools.     

A quantitative model for software engineering trends

Many decision-makers in industry, government and academia routinely make decisions whose outcome depends on the evolution of software technology trends. Even though the stakes of these decisions are usually very high, decision makers routinely depend on expert opinions and qualitative assessments to model the evolution of software technology; both of these sources of decision-making information are subjective, are based on opinions rather than facts, and are prone to error. In this paper, we report on our ongoing work to build quantitative models of the evolution of software technology trends. In particular, we discuss how we took specific evolutionary models and merged them into a single (general-purpose) model. The original specific models are derived empirically using statistical methods on trend data we had collected over several years, and have been validated individually; in this paper we further validate the generic (general-purpose) model.     

A process model for component-oriented software engineering

The investigation of reuse has a long history, eventually maturing into the "build by integration" paradigm. Meanwhile, component technologies also improved along with engineering practices. What is missing is a methodology that uses components within such a paradigm, thus bridging the gap. The authors propose a model devoted to complete component orientation, rather than modifying object-oriented approaches to accommodate components. They investigate component-based technologies to address new needs and, consequently, to integrate adequate practices toward a consistent process model.     

A software size model

A bottom-up approach to software size estimation is described. It first identifies factors affecting software size, thus obtaining size explanation equations, and then seeks suitable predictors based on those explanation factors which can be used for size estimation. The approach, or model, is bottom-up in that it sizes individual software components or modules first, and then obtains subsystem and system sizes by summing component sizes. Since components may have different purposes and characteristics, the model allows for the partitioning of system components into several different types, each component type having different size explanation and estimation equations. The partitioning is not fixed, but depends on the particular software development technology. The model is applied to several different software systems, including both business applications and systems programs     

A comprehensive quality model for service-oriented systems

In a service-oriented system, a quality (or Quality of Service) model is used (i) by service requesters to specify the expected quality levels of service delivery; (ii) by service providers to advertise quality levels that their services achieve; and (iii) by service composers when selecting among alternative services those that are to participate in a service composition. Expressive quality models are needed to let requesters specify quality expectations, providers advertise service qualities, and composers finely compare alternative services. Having observed many similarities between various quality models proposed in the literature, we review these and integrate them into a single quality model, called QVDP. We highlight the need for integration of priority and dependency information within any quality model for services and propose precise submodels for doing so. Our intention is for the proposed model to serve as a reference point for further developments in quality models for service-oriented systems. To this aim, we extend the part of the UML metamodel specialized for Quality of Service with QVDP concepts unavailable in UML.

A staged model for the software life cycle

Software engineers have traditionally considered any work after initial delivery as simply software maintenance. Some researchers have divided this work into various tasks, including making changes to functionality (perfective), changing the environment (adaptive), correcting errors (corrective), and making improvements to avoid future problems (preventive). However, many have considered maintenance basically uniform over time. Because software development has changed considerably since its early days, the authors believe this approach no longer suffices. They describe a new view of the software life cycle in which maintenance is actually a series of distinct stages, each with different activities, tools, and business consequences. While the industry still considers postdelivery work as simply software maintenance, the authors claim that the process actually falls into stages. They think both business and engineering can benefit from understanding these stages and their transitions     

A framework for evaluating a software bidding model

This paper discusses the issues involved in evaluating a software bidding model. We found it difficult to assess the appropriateness of any model evaluation activities without a baseline or standard against which to assess them. This paper describes our attempt to construct such a baseline. We reviewed evaluation criteria used to assess cost models and an evaluation framework that was intended to assess the quality of requirements models. We developed an extended evaluation framework and an associated evaluation process that will be used to evaluate our bidding model. Furthermore, we suggest the evaluation framework might be suitable for evaluating other models derived from expert-opinion based influence diagrams.     

A causal model for software cost estimating error

Software cost estimation is an important concern for software managers and other software professionals. The hypothesized model in this research suggests that an organization's use of an estimate influences its estimating practices which influence both the basis of the estimating process and the accuracy of the estimate. The model also suggests that the estimating basis directly influences the accuracy of the estimate. A study of business information systems managers and professionals at 112 different organizations using causal analysis with the Equations Modeling System (EQS) refined the model. The refined model shows that no managerial practice in this study discourages the use of intuition, guessing and personal memory in cost estimating. Although user commitment and accountability appear to foster algorithm-based estimating, such an algorithmic basis does not portend greater accuracy. Only one managerial practice-the use of the estimate in performance evaluations of software managers and professionals-presages greater accuracy. By implication, the research suggests somewhat ironically that the most effective approach to improve estimating accuracy may be to make estimators, developers and managers more accountable for the estimate even though it may be impossible to direct them explicitly on how to produce a more accurate one     

A probabilistic model for predicting software development effort

Recently, Bayesian probabilistic models have been used for predicting software development effort. One of the reasons for the interest in the use of Bayesian probabilistic models, when compared to traditional point forecast estimation models, is that Bayesian models provide tools for risk estimation and allow decision-makers to combine historical data with subjective expert estimates. In this paper, we use a Bayesian network model and illustrate how a belief updating procedure can be used to incorporate decision-making risks. We develop a causal model from the literature and, using a data set of 33 real-world software projects, we illustrate how decision-making risks can be incorporated in the Bayesian networks. We compare the predictive performance of the Bayesian model with popular nonparametric neural-network and regression tree forecasting models and show that the Bayesian model is a competitive model for forecasting software development effort.