Survey of reliability and availability prediction methods from the viewpoint of software architecture

Many future software systems will be distributed across a network, extensively providing different kinds of services for their users. These systems must be highly reliable and provide services when required. Reliability and availability must be engineered into software from the onset of its development, and potential problems must be detected in the early stages, when it is easier and less expensive to implement modifications. The software architecture design phase is the first stage of software development in which it is possible to evaluate how well the quality requirements are being met. For this reason, a method is needed for analyzing software architecture with respect to reliability and availability. In this paper, we define a framework for comparing reliability and availability analysis methods from the viewpoint of software architecture. Our contribution is the comparison of the existing analysis methods and techniques that can be used for reliability and availability prediction at the architectural level. The objective is to discover which methods are suitable for the reliability and availability prediction of today’s complex systems, what are the shortcomings of the methods, and which research activities need to be conducted in order to overcome these identified shortcomings. The comparison reveals that none of the existing methods entirely fulfill the requirements that are defined in the framework. The comparison framework also defines the characteristics required of new reliability and availability analysis methods. Additionally, the framework is a valuable tool for selecting the best suitable method for architecture analysis. Furthermore, the framework can be extended and used for other evaluation methods as well.     

Usability and software architecture

The role of software architecture with respect to usability has evolved over the past 20 years. The architectures of the 1980s and early 1990s assumed that usability was primarily a property of the presentation of information. Therefore, simply separating the presentation from the dialogue and application made it easy to modify that presentation after user testing. A more popular belief in the 1990s was that usability concerns greatly affected system functionality as well as the presentation. This emphasis took attention away from architectural support (beyond separation). Achieving the correct functionality for a given system became paramount. It is our observation that even if presentation and functionality of a system are well designed, the usability of a system can be greatly compromised if the underlying architecture does not support human concerns beyond modifiability. This paper will present a new role for software architecture in usability, preliminary research and practice stemming from this role and a research agenda for the future.     

A model-driven approach for the derivation of architectural requirements of software product lines

The alignment of the software architecture and the functional requirements of a system is a demanding task because of the difficulty in tracing design elements to requirements. The four-step rule set (4SRS) is a unified modeling language (UML)-based model-driven method for single system development which provides support to the software architect in this task. This paper presents an evolution of the 4SRS method aimed at software product lines. In particular, we describe how to address the transformation of functional requirements (use cases) into component-based requirements for the product line architecture. The result is a UML-based model-driven method that can be applied in combination with metamodeling tools such as the eclipse modeling framework (EMF) to derive the architecture of software product lines. We present our approach in a practical way and illustrate it with an example. We also discuss how our proposals are related to the work of other authors.     

Exploring the benefits of the combination of a software architecture analysis and a usability evaluation of a mobile application

Designing easy to use mobile applications is a difficult task. In order to optimize the development of a usable mobile application, it is necessary to consider the mobile usage context for the design and the evaluation of the user-system interaction of a mobile application. In our research we designed a method that aligns the inspection method “Software ArchitecTure analysis of Usability Requirements realizatioN” SATURN and a mobile usability evaluation in the form of a user test. We propose to use mobile context factors and thus requirements as a common basis for both inspection and user test. After conducting both analysis and user test, the results described as usability problems are mapped and discussed. The mobile context factors identified define and describe the usage context of a mobile application. We exemplify and apply our approach in a case study. This allows us to show how our method can be used to identify more usability problems than with each method separately. Additionally, we could confirm the validity and identified the severity of usability problems found by both methods. Our work presents how a combination of both methods allows to address usability issues in a more holistic way. We argue that the increased quantity and quality of results can lead to a reduction of the number of iterations required in early stages of an iterative software development process.     

Software development methods and usability: Perspectives from a survey in the software industry in Norway

This paper investigates the relationship between software development methodologies and usability. The point of departure is the assumption that two important disciplines in software development, one of software development methods (SDMs) and one of usability work, are not integrated in industrial software projects.

Building on previous research we investigate two questions; (1) Will software companies generally acknowledge the importance of usability, but not prioritise it in industrial projects? and (2) To what degree are software development methods and usability perceived by practitioners as being integrated? To this end a survey in the Norwegian IT industry was conducted. From a sample of 259 companies we received responses from 78 companies.

In response to our first research question, our findings show that although there is a positive bias towards usability, the importance of usability testing is perceived to be much less than that of usability requirements. Given the strong time and cost pressures associated with the software industry, we believe that these results highlight that there is a gap between intention and reality. Regarding our second research question our survey revealed that companies perceive usability and software development methods to be integrated. This is in contrast to earlier research, which, somewhat pessimistically, has argued for the existence of two different cultures, one of software development and one of usability. The findings give hope for the future, in particular because the general use of system development methods are pragmatic and adaptable.     

A bargaining-specific architecture for supporting automated service agreement negotiation systems

The provision of services is often regulated by means of agreements that must be negotiated beforehand. Automating such negotiations is appealing insofar as it overcomes one of the most often cited shortcomings of human negotiation: slowness. Our analysis of the requirements of automated negotiation systems in open environments suggests that some of them cannot be tackled in a protocol-independent manner, which motivates the need for a protocol-specific architecture. However, current state-of-the-art bargaining architectures fail to address all of these requirements together. Our key contribution is a bargaining architecture that addresses all of the requirements we have identified. The definition of the architecture includes a logical view that identifies the key architectural elements and their interactions, a process view that identifies how the architectural elements can be grouped together into processes, a development view that includes a software framework that provides a reference implementation developers can use to build their own negotiation systems, and a scenarios view by means of which the architecture is illustrated and validated.     

Integrating usability requirements that can be evaluated in design time into Model Driven Engineering of Web Information Systems

In recent years, Web Engineering development projects have grown increasingly complex for and critical to the smooth running of organizations. However, recent studies reveal that a high percentage of these projects fail to attain the quality parameters required by stakeholders. The inadequate consideration of requirements management activities together with the absence of attention to the elicitation and evaluation of requirements and metrics related to certain quality attributes which are of special importance in this kind of systems, such as usability, have proved to be some of the main causes of this failure. This paper attempts to reduce some of the quality failures detected in Web Engineering development projects by proposing the consideration and evaluation of quality attributes from early stages of the development process. The presented approach therefore commences with a reinforcement of the requirements related activities in this discipline, which is carried out by using a requirements metamodel. Once these requirements have been identified, the approach focuses on the extension of the conceptual models used by Web Engineering methodologies with the aim of allowing the explicit consideration of usability requirements along with the evaluation of quality metrics during the design of the system. An example of an application illustrating how the approach can be used, along with the automatic support which was developed for it, are also shown.     

Investigating and promoting UX practice in industry: An experimental study

The efforts of addressing user experience (UX) in product development keep growing, as demonstrated by the proliferation of workshops and conferences bringing together academics and practitioners, who aim at creating interactive software able to satisfy their users. This special issue focuses on “Interplay between User Experience Evaluation and Software Development”, stating that the gap between human-computer interaction and software engineering with regard to usability has somewhat been narrowed. Unfortunately, our experience shows that software development organizations perform few usability engineering activities or none at all. Several authors acknowledge that, in order to understand the reasons of the limited impact of usability engineering and UX methods, and to try to modify this situation, it is fundamental to thoroughly analyze current software development practices, involving practitioners and possibly working from inside the companies. This article contributes to this research line by reporting an experimental study conducted with software companies. The study has confirmed that still too many companies either neglect usability and UX, or do not properly consider them. Interesting problems emerged. This article gives suggestions on how they may be properly addressed, since their solution is the starting point for reducing the gap between research and practice of usability and UX. It also provides further evidence on the value of the research method, called Cooperative Method Development, based on the collaboration of researchers and practitioners in carrying out empirical research; it has been used in a step of the performed study and has revealed to be instrumental for showing practitioners why to improve their development processes and how to do so.     

SPI success factors within product usability evaluation

This article presents an experience report where we compare 8 years of experience of product related usability testing and evaluation with principles for software process improvement (SPI). In theory the product and the process views are often seen to be complementary, but studies of industry have demonstrated the opposite. Therefore, more empirical studies are needed to understand and improve the present situation. We find areas of close agreement as well as areas where our work illuminates new characteristics. It has been identified that successful SPI is dependent upon being successfully combined with a business orientation. Usability and business orientation also have strong connections although this has not been extensively addressed in SPI publications. Reasons for this could be that usability focuses on product metrics whilst today's SPI mainly focuses on process metrics. Also because today's SPI is dominated by striving towards a standardized, controllable, and predictable software engineering process; whilst successful usability efforts in organisations are more about creating a creative organisational culture advocating a useful product throughout the development and product life cycle. We provide a study and discussion that supports future development when combining usability and product focus with SPI, in particular if these efforts are related to usability process improvement efforts.     

Bridging patterns: An approach to bridge gaps between SE and HCI

Adding usability improving solutions during late stage development is to some extent restricted by the software architecture. However, few software engineers and human–computer interaction engineers are aware of this important constraint and as a result avoidable rework is frequently necessary. In this paper we present a new type of pattern called a bridging pattern. Bridging patterns extend interaction design patterns by adding information on how to generally implement this pattern. Bridging patterns can be used for architectural analysis: when the generic implementation is known, software architects can assess what it means in their context and can decide whether they need to modify the software architecture to support these patterns. This may prevent part of the high costs incurred by adaptive maintenance activities once the system has been implemented and leads to architectures with better support for usability.     

Software architecture awareness in long-term software product evolution

Software architecture has been established in software engineering for almost 40 years. When developing and evolving software products, architecture is expected to be even more relevant compared to contract development. However, the research results seem not to have influenced the development practice around software products very much. The architecture often only exists implicitly in discussions that accompany the development. Nonetheless many of the software products have been used for over 10, or even 20 years. How do development teams manage to accommodate changing needs and at the same time maintain the quality of the product? In order to answer this question, grounded theory study based on 15 semi-structured interviews was conducted in order to find out about the wide spectrum of architecture practices in software product developing organisations. Our results indicate that a chief architect or central developer acts as a ‘walking architecture’ devising changes and discussing local designs while at the same time updating his own knowledge about problematic aspects that need to be addressed. Architecture documentation and representations might not be used, especially if they replace the feedback from on-going developments into the ‘architecturing’ practices. Referring to results from Computer Supported Cooperative Work, we discuss how explicating the existing architecture needs to be complemented by social protocols to support the communication and knowledge sharing processes of the ‘walking architecture’.     

Estimating software readiness using predictive models

In this study, defect tracking is used as a proxy method to predict software readiness. The number of remaining defects in an application under development is one of the most important factors that allow one to decide if a piece of software is ready to be released. By comparing predicted number of faults and number of faults discovered in testing, software manager can decide whether the software is likely ready to be released or not.The predictive model developed in this research can predict: (i) the number of faults (defects) likely to exist, (ii) the estimated number of code changes required to correct a fault and (iii) the estimated amount of time (in minutes) needed to make the changes in respective classes of the application. The model uses product metrics as independent variables to do predictions. These metrics are selected depending on the nature of source code with regards to architecture layers, types of faults and contribution factors of these metrics. The use of neural network model with genetic training strategy is introduced to improve prediction results for estimating software readiness in this study. This genetic-net combines a genetic algorithm with a statistical estimator to produce a model which also shows the usefulness of inputs.The model is divided into three parts: (1) prediction model for presentation logic tier (2) prediction model for business tier and (3) prediction model for data access tier. Existing object-oriented metrics and complexity software metrics are used in the business tier prediction model. New sets of metrics have been proposed for the presentation logic tier and data access tier. These metrics are validated using data extracted from real world applications. The trained models can be used as tools to assist software mangers in making software release decisions.     

基于软件总线的小卫星系统软件可重用结构设计

提出了一种小型探测卫星系统软件的可重用性结构设计方法。为实现可重用性,软件结构采用了模块化策略,各任务模块间相互通信采用了“软件总线”概念。软件总线为每个任务模块提供一个简单的标准化数据通信接口,因此对某一星载系统任务模块的修改或增加或替换时不影响其它任务模块,同时某些场合,卖命通过对地面上实时地改变软件总线上的调度表内容的方法,很容易改变卫星的工作状态。在星载系统软件软件开发周期内,各任务模块通     

基于C/S的软件体系结构研究

面向对象的技术为人们带来了无限希望和与软件危机做斗争的工具。该文介绍了以面向对象的技术为基础,以软件体系结构为核心的软件开发过程,描述了如何从软件体系结构的观点去考虑C/S系统,以达到最大限度的设计复用。     

Controlling software architecture erosion: A survey

Software architectures capture the most significant properties and design constraints of software systems. Thus, modifications to a system that violate its architectural principles can degrade system performance and shorten its useful lifetime. As the potential frequency and scale of software adaptations increase to meet rapidly changing requirements and business conditions, controlling such architecture erosion becomes an important concern for software architects and developers. This paper presents a survey of techniques and technologies that have been proposed over the years either to prevent architecture erosion or to detect and restore architectures that have been eroded. These approaches, which include tools, techniques and processes, are primarily classified into three generic categories that attempt to minimise, prevent and repair architecture erosion. Within these broad categories, each approach is further broken down reflecting the high-level strategies adopted to tackle erosion. These are: process-oriented architecture conformance, architecture evolution management, architecture design enforcement, architecture to implementation linkage, self-adaptation and architecture restoration techniques consisting of recovery, discovery and reconciliation. Some of these strategies contain sub-categories under which survey results are presented.We discuss the merits and weaknesses of each strategy and argue that no single strategy can address the problem of erosion. Further, we explore the possibility of combining strategies and present a case for further work in developing a holistic framework for controlling architecture erosion.     

面向不确定需求的适应性软件体系结构设计

需求不确定性是软件开发的主要风险来源之一。首先讨论了不确定需求的含义、产生的原因及其影响;然后分析了需求与软件体系结构的关系;指出了软件体系结构对满足需求和控制软件风险的重要性;提出了在不确定需求的情形下,需求分析与体系结构设计的协同建模方法及适应性软件体系结构的设计思想;论证了不确定需求情形下软件体系结构的演化过程,以保障生命周期内软件产品质量的开发思路。     

一种从组织业务数据中获取软件需求的方法

针对隐藏于组织业务海量数据中的隐性软件需求获取提出一种方法。该方法的基本思想是：组织业务海量数据中隐含软件需求,它是以隐性知识形式存在于海量数据中的,隐性知识利用的解决方案就是组织及利益相关者对待开发软件系统的要求（软件需求）。首先,构建一个完整的、无冲突的、正确的待开发软件系统目标及其关系模型,并在待开发系统目标指导下,利用数据挖掘技术对数据进行挖掘,从中发现隐性知识;然后,识别知识的有用性和可用性;最后为可用性知识的利用提供解决方案。进而获取隐藏于大量数据中的隐性软件需求．     

How do architecture patterns and tactics interact? A model and annotation

Software architecture designers inevitably work with both architecture patterns and tactics. Architecture patterns describe the high-level structure and behavior of software systems as the solution to multiple system requirements, whereas tactics are design decisions that improve individual quality attribute concerns. Tactics that are implemented in existing architectures can have significant impact on the architecture patterns in the system. Similarly, tactics that are selected during initial architecture design significantly impact the architecture of the system to be designed: which patterns to use, and how they must be changed to accommodate the tactics. However, little is understood about how patterns and tactics interact. In this paper, we develop a model for the interaction of patterns and tactics that enables software architects to annotate architecture diagrams with information about the tactics used and their impact on the overall structure. This model is based on our in-depth analysis of the types of interactions involved, and we show several examples of how the model can be used to annotate different kinds of architecture diagrams. We illustrate the model and annotation by showing examples taken from real systems, and describe how the annotation was used in architecture reviews. Tactics and patterns are known architectural concepts; this work provides more specific and in-depth understanding of how they interact. Its other key contribution is that it explores the larger problem of understanding the relation between strategic decisions and how they need to be tailored in light of more tactical decisions.     

基于感知控制的代理体系结构模型

提出一个基于感知控制代理的体系结构模型,旨在建模高可用的交互式软件系统.该模型通过增加新的体系结构层次来显式地建模可用性需求,以实现不同可用性特征之间的正交关系,并采用感知控制理论来匹配用户界面和应用核心之间的非线性关系.与现有的体系结构模型相比,该模型不仅使系统能够呈现用户任务层次的界面元素,而且允许用户在任务层次上对系统进行操作,从而使用户以更自然的方式控制系统来完成任务,实现目标.此外,采用该模型的系统还可以实现可用性的动态扩充.