Costs and benefits of early defect detection: experiences from developing client server and host applications

Defect detection activities are generally seen as expensive and time consuming. This article reports on actual experiences from large projects. Based on data, dependencies between the costs of early defect detection, late defect detection and defect fixing are analysed and some guidelines are derived for timing and resource allocation to ensure cost-effective defect detection. Experience reports show that the costs of defect fixing in software development grow dramatically when the defects are found late, i.e. when the defects have already influenced the next phase. This common experience is supported by all the projects, two of which are considered in this paper. However, metrics applied to the data show that it is not always an order of magnitude that lies between the costs of early and late fixing of defects. Rather, the average cost of defects found late decreases with introduction of early defect detection. This is due to the fact that early document reviews leave only minor defects, e.g. in the requirements or the design. Major and therefore expensive defects tend to be found in those early reviews. Further analysis of the data led to the use of metrics that proved very useful when planning and executing the required defect detection activities. For example the number of remarks per 100 lines was used to decide how efficient reviews of the design have been and whether more or less resources should be allocated to these reviews in a running project. As a conclusion, it is emphasized that a substantial amount of a project's budget and time will be saved by introducing systematic defect detection early in the project. It is suggested that defect detection activities should start as soon as the requirements documents are declared finished.     

Temporal specialization and generalization

A standard relation has two dimensions: attributes and tuples. A temporal relation contains two additional orthogonal time dimensions: valid time records when facts are true in the modeled reality, and transaction time records when facts are stored in the temporal relation. Although there are no restrictions between the valid time and transaction time associated with each fact, in many practical applications the valid and transaction times exhibit restricted interrelationships that define several types of specialized temporal relations. This paper examines areas where different specialized temporal relations are present. In application systems with multiple, interconnected temporal relations, multiple time dimensions may be associated with facts as they flow from one temporal relation to another. The paper investigates several aspects of the resulting generalized temporal relations, including the ability to query a predecessor relation from a successor relation. The presented framework for generalization and specialization allows one to precisely characterize and compare temporal relations and the application systems in which they are embedded. The framework's comprehensiveness and its use in understanding temporal relations are demonstrated by placing previously proposed temporal data models within the framework. The practical relevance of the defined specializations and generalizations is illustrated by sample realistic applications in which they occur. The additional semantics of specialized relations are especially useful for improving the performance of query processing     

Abstraction and specialization of information granules

In his paper, we introduce a model of generalization and specialization of information granules. The information granules themselves are modeled as fuzzy sets or fuzzy relations. The generalization is realized by or-ing fuzzy sets while the specialization is completed through logic and operation. These two logic operators are realized using triangular norms (that is t- and a-norms). We elaborate on two (top-down and bottom-up) strategies of constructing information granules that arise as results of generalization and specialization. Various triangular norms are experimented with and some conclusions based on numeric studies are derived.     

Problems, methods and specialization

The large aspiration to place the whole of software development alongside the established branches as one more branch of engineering is misconceived. The author discusses how our aspiration should be to develop specialized branches of software engineering, each meriting its own place alongside the specialized established branches     

Just-in-time value specialization

JavaScript emerges today as one of the most important programming languages for the development of client-side web applications. Therefore, it is essential that browsers be able to execute JavaScript programs efficiently. However, the dynamic nature of this programming language makes it very challenging to achieve this much needed efficiency. In this paper we propose parameter-based value specialization as a way to improve the quality of the code produced by JIT engines. We have empirically observed that almost 60% of the JavaScript functions found in the world's 100 most popular websites are called only once, or are called with the same parameters. Capitalizing on this observation, we adapt a number of classic compiler optimizations to specialize code based on the runtime values of function's actual parameters. We have implemented the techniques proposed in this paper in IonMonkey, an industrial quality JavaScript JIT compiler developed at the Mozilla Foundation. Our experiments, run across three popular JavaScript benchmarks, SunSpider, V8 and Kraken, show that, in spite of its highly speculative nature, our optimization pays for itself. As an example, we have been able to speed up V8 by 4.83%, and to reduce the size of its generated native code by 18.84%.     

Class hierarchy specialization

Many class libraries are designed with an emphasis on generality and extensibility. Applications often exercise only part of a library's functionality. As a result, the objects created by an application may contain unused (user-specified or compiler-generated) members. Redundant members in objects are undesirable because they increase an application's memory usage. We present an algorithm for specializing a class hierarchy with respect to its usage in a program . That is, the algorithm analyzes the member access patterns for 's variables, and creates distinct classes for variables that access different members. The algorithm addresses the inheritance mechanisms of C++ in their full generality, including multiple inheritance and virtual (shared) inheritance. Class hierarchy specialization reduces object size, and can be viewed as a space optimization. However, execution time may also be reduced through reduced object creation or destruction time, and caching and paging effects. Class hierarchy specialization may also create new opportunities for existing optimizations such as call devirtualization and inlining. In addition, specialization may be useful in tools for software maintenance and program understanding. Received: 11 May 1999 / 14 December 1999     

Feedback-directed specialization of code

Based on feedback information, a large number of optimizations can be performed by the compiler. This information actually indicates the changing behavior of the applications and can be used to specialize code accordingly.Code specialization is a way to facilitate the compiler to perform optimizations by providing the information regarding variables in the code. It is however difficult to select the variables which maximize the benefit of specialization. Also the overhead of specialization and code size increase are the main issues while specializing code.This paper suggests a novel method for improving the performance using specialization based on feedback information and analysis. The code is iteratively specialized after selecting candidate variables by using a heuristic, followed by generation of optimized templates. These templates require a limited set of instructions to be specialized at runtime and are valid for a large number of values. The overhead of runtime specialization is further minimized through optimal software cache of template clones whose instantiation can be performed at static compile time.The experiments have been performed on Itanium-II(IA-64) and Pentium-IV processors using icc and gcc compilers. A significant improvement in terms of execution speed and reduction of code size has been achieved for SPEC and FFTW benchmarks.     

Evolving team behaviors with specialization

This article evaluates Collective Neuro-Evolution (CONE), a cooperative co-evolutionary method for solving collective behavior tasks and increasing task performance via facilitating behavioral specialization in agent teams. Specialization is used as a problem solving mechanism, and its emergence is guided and regulated by CONE. CONE is comparatively evaluated with related methods in a simulated evolutionary robotics pursuit-evasion task. This task required multiple pursuer robots to cooperatively capture evader robots. Results indicate that CONE is appropriate for evolving specialized behaviors. The interaction of specialized behaviors produces behavioral heterogeneity in teams and collective prey capture behaviors that yield significantly higher performances compared to related methods.     

Ergonomics--costs and benefits

Ergonomics is primarily concerned with improving the performance of man or of man-machine systems. Although many applications have produced evident improvements, the terms of reference and the results are not often expressed in measures that are easily converted into financial savings. However, there is a growing demand for cost-benefit data of ergonomic improvements, and several examples in which the application of ergonomic principles has resulted in tangible benefits, are reviewed.Cases are cited of increases of productivity resulting from equipment redesign and of savings achieved from the reduction of accidents, and from improvements in the working environment. It is concluded that there is, as yet, no large body of well-documented cases of financial savings accruing from the application of ergonomics, due in many cases to the difficulties of costing actual changes in performance in the work situation. The need for further studies is debated, and it is suggested that the use of ergonomic data in a design programme should not necessarily be based on the prediction of financial benefits.     

Software specialization via symbolic execution

A technique and an environment-supporting specialization of generalized software components are described. The technique is based on symbolic execution. It allows one to transform a generalized software component into a more specific and more efficient component. Specialization is proposed as a technique that improves software reuse. The idea is that a library of generalized components exists and the environment supports a designer in customizing a generalized component when the need arises for reusing it under more restricted conditions. It is also justified as a reengineering technique that helps optimize a program during maintenance. Specialization is supported by an interactive environment that provides several transformation tools: a symbolic executor/simplifier, an optimizer, and a loop refolder. The conceptual basis for these transformation techniques is described, examples of their application are given, and how they cooperate in a prototype environment for the Ada programming language is outlined     

结对编程成本与收益之探

结对编程(Pair Programming)是极限编程(Extreme Programming)的十二个实践之一,是团队设计的基础。它是指两个开发人员共用一台计算机,其中一个人负责具体细节,另一个人关注整体,并且这两人的角色可以随时交换。本文通过一个项目的运作过程的试验实例,分析结对编程的成本和收益。结对编程的优势在于：改进设计质量、减少程序缺陷、降低人员风险、提高技术技能和团队合作精神。为中小型企业软件过程改进提供了具有相当经济意义的方案,推动企业生产力、企业文化改进。     

Ergonomics--costs and benefits revisited

An earlier review reported a dozen cases where ergonomics applications had resulted in cost savings. A large number of publications which refer to the topics of the cost-effectiveness and cost-benefits of ergonomics can now be found. However, data showing the value of ergonomics applications remain scarce. Cost-benefit and cost-effectiveness studies are difficult to conduct for a number of reasons. While it is unlikely that the general case for the value of ergonomics can be proven, ergonomists must be in a position to discuss the potential costs and benefits of their work with clients. The Business case model is suggested as one way to structure an analysis of where a potential ergonomics application might reduce the risks to costs or the possibility of lost benefits.     

Understanding the cortical specialization for horizontal disparity

Because the eyes are displaced horizontally, binocular vision is inherently anisotropic. Recent experimental work has uncovered evidence of this anisotropy in primary visual cortex (V1): neurons respond over a wider range of horizontal than vertical disparity, regardless of their orientation tuning. This probably reflects the horizontally elongated distribution of two-dimensional disparity experienced by the visual system, but it conflicts with all existing models of disparity selectivity, in which the relative response range to vertical and horizontal disparities is determined by the preferred orientation. Potentially, this discrepancy could require us to abandon the widely held view that processing in V1 neurons is initially linear. Here, we show that these new experimental data can be reconciled with an initial linear stage; we present two physiologically plausible ways of extending existing models to achieve this. First, we allow neurons to receive input from multiple binocular subunits with different position disparities (previous models have assumed all subunits have identical position and phase disparity). Then we incorporate a form of divisive normalization, which has successfully explained many response properties of V1 neurons but has not previously been incorporated into a model of disparity selectivity. We show that either of these mechanisms decouples disparity tuning from orientation tuning and discuss how the models could be tested experimentally. This represents the first explanation of how the cortical specialization for horizontal disparity may be achieved.     

Requirements-Based Estimation of Change Costs

We present a case study that aimsat quantitative assessment of the impact of requirements changes,and quantitative estimation of costs of the development activitiesthat must be carried out to accomplish those changes. Our approachis based on enhanced traceability and an integrated view of theprocess and product models. The elements in the process and productmodels are quantitatively characterised through proper measurement,thus achieving a sound basis for different kinds of sophisticatedanalysis concerning the impact of requirements changes and theircosts. We present the results of the application of modelingand measurement to an industrial project dealing with real-timesoftware development. The ability to predict the impact of changesin requirements and the cost of related activities is shown.     

Software reuse by specialization of generic procedures throughviews

A generic procedure can be specialized, by compilation through views, to operate directly on concrete data. A view is a computational mapping that describes how a concrete type implements an abstract type. Clusters of related views are needed for specialization of generic procedures that involve several types or several views of a single type. A user interface that reasons about relationships between concrete types and abstract types allows view clusters to be created easily. These techniques allow rapid specialization of generic procedures for applications     

ERP plans and decision-support benefits

Management and implementation of Enterprise Resource Planning (ERP) systems have tended to concentrate on their transactional and record-keeping aspects, rather than on their decision-support capabilities. This paper explores connections between ERP systems and decision support based on the perceptions of 53 ERP system adopters. It offers new insights into the important objectives that are (and should be) considered in ERP plans, including decision-support objectives. It provides insights into the decision-support benefits of ERP systems. The study also examines relationships between the importance of various objectives in ERP planning and the subsequent realization of decision-support benefits from an ERP system.     

Considering Costs in Networking

A few years ago, the information systems world braced itself for the “year of the network.” Major announcements of networking hardware and systems were anticipated, and generally the trade press agreed that this important technology was about to make its mark on the IS community. Obviously, the reality has not lived up to the expectations. However, its still evident that most organizations using computers will engage in some level of networking technology, and those that do must be aware of the economic implications.     

Bagging with Adaptive Costs

Ensemble methods have proven to be highly effective in improving the performance of base learners under most circumstances. In this paper, we propose a new algorithm that combines the merits of some existing techniques, namely, bagging, arcing, and stacking. The basic structure of the algorithm resembles bagging. However, the misclassification cost of each training point is repeatedly adjusted according to its observed out-of-bag vote margin. In this way, the method gains the advantage of arcing-building the classifier the ensemble needs - without fixating on potentially noisy points. Computational experiments show that this algorithm performs consistently better than bagging and arcing with linear and nonlinear base classifiers. In view of the characteristics of bacing, a hybrid ensemble learning strategy, which combines bagging and different versions of bacing, is proposed and studied empirically.     

Considering Costs in Networking

A few years ago, the information systems world braced itself for the “year of the network.” Major announcements of networking hardware and systems were anticipated, and generally the trade press agreed that this important technology was about to make its mark on the IS community. Obviously, the reality has not lived up to the expectations. However, its still evident that most organizations using computers will engage in some level of networking technology, and those that do must be aware of the economic implications.