The DOPLER meta-tool for decision-oriented variability modeling: a multiple case study

The variability of a product line is typically defined in models. However, many existing variability modeling approaches are rigid and don’t allow sufficient domain-specific adaptations. We have thus been developing a flexible and extensible approach for defining product line variability models. Its main purposes are to guide stakeholders through product derivation and to automatically generate product configurations. Our approach is supported by the DOPLER (Decision-Oriented Product Line Engineering for effective Reuse) meta-tool that allows modelers to specify the types of reusable assets, their attributes, and dependencies for their specific system and context. The aim of this paper is to investigate the suitability of our approach for different domains. More specifically, we explored two research questions regarding the implementation of variability and the utility of DOPLER for variability modeling in different domains. We conducted a multiple case study consisting of four cases in the domains of industrial automation systems and business software. In each of these case studies we analyzed variability implementation techniques. Experts from our industry partners then developed domain-specific meta-models, tool extensions, and variability models for their product lines using DOPLER. The four cases demonstrate the flexibility of the DOPLER approach and the extensibility and adaptability of the supporting meta tool.     

Supporting distributed product configuration by integrating heterogeneous variability modeling approaches

ContextIn industrial settings products are developed by more than one organization. Software vendors and suppliers commonly typically maintain their own product lines, which contribute to a larger (multi) product line or software ecosystem. It is unrealistic to assume that the participating organizations will agree on using a specific variability modeling technique—they will rather use different approaches and tools to manage the variability of their systems.ObjectiveWe aim to support product configuration in software ecosystems based on several variability models with different semantics that have been created using different notations.MethodWe present an integrative approach that provides a unified perspective to users configuring products in multi product line environments, regardless of the different modeling methods and tools used internally. We also present a technical infrastructure and a prototype implementation based on web services.ResultsWe show the feasibility of the approach and its implementation by using it with the three most widespread types of variability modeling approaches in the product line community, i.e., feature-based, OVM-style, and decision-oriented modeling. To demonstrate the feasibility and flexibility of our approach, we present an example derived from industrial experience in enterprise resource planning. We further applied the approach to support the configuration of privacy settings in the Android ecosystem based on multiple variability models. We also evaluated the performance of different model enactment strategies used in our approach.ConclusionsTools and techniques allowing stakeholders to handle variability in a uniform manner can considerably foster the initiation and growth of software ecosystems from the perspective of software reuse and configuration.     

Toward automated feature model configuration with optimizing non-functional requirements

ContextA software product line is a family of software systems that share some common features but also have significant variabilities. A feature model is a variability modeling artifact, which represents differences among software products with respect to the variability relationships among their features. Having a feature model along with a reference model developed in the domain engineering lifecycle, a concrete product of the family is derived by binding the variation points in the feature model (called configuration process) and by instantiating the reference model.ObjectiveIn this work we address the feature model configuration problem and propose a framework to automatically select suitable features that satisfy both the functional and non-functional preferences and constraints of stakeholders. Additionally, interdependencies between various non-functional properties are taken into account in the framework.MethodThe proposed framework combines Analytical Hierarchy Process (AHP) and Fuzzy Cognitive Maps (FCM) to compute the non-functional properties weights based on stakeholders’ preferences and interdependencies between non-functional properties. Afterwards, Hierarchical Task Network (HTN) planning is applied to find the optimal feature model configuration.ResultOur approach improves state-of-art of feature model configuration by considering positive or negative impacts of the features on non-functional properties, the stakeholders’ preferences, and non-functional interdependencies. The approach presented in this paper extends earlier work presented in [1] from several distinct perspectives including mechanisms handling interdependencies between non-functional properties, proposing a novel tooling architecture, and offering visualization and interaction techniques for representing functional and non-functional aspects of feature models.Conclusionour experiments show the scalability of our configuration approach when considering both functional and non-functional requirements of stakeholders.     

Context-dependent product line engineering with lightweight formal approaches

This paper proposes a new style of product line engineering methods. It focuses on constructing embedded systems that take into account the contexts such as the external physical environments. In current product line development projects, Feature Analysis is mainly conducted from the viewpoint of system configurations: how hardware and software components are configured to constitute a system. In most cases, contexts are not considered explicitly. As a result, unexpected and unfavorable behavior might emerge in a system if a developer does not recognize any possible conflicting combinations between the system and contexts. To deal with this problem, this paper provides the notion of a context-dependent product line, which is composed of the system and context lines. The former is obtained by analyzing a family of systems. The latter is obtained by analyzing features of contexts associated to the systems. The system and context lines contain reusable core assets. The configuration of selected system components and contexts can be formally checked at the specification level. In this paper, we show a development process that includes the creation of both product line assets as well as context assets.     

WISDOM: A website design method based on reusing design and software solutions

ContextWebsites are increasingly important for advertising and announcing information and they have become virtual business operations support tools. Thus, website designers have to take an increasing number of criteria (cost, delay, quality, security, maintenance) into account during design process to satisfy the needs.ObjectiveThe objective of this paper was to present our WISDOM method that: guides the designer through the website design process, proposes design solutions based on already existing solutions for online website design, facilitates the choice of software components to implement specific services, and speeds up website construction.MethodThe originality of our method is that it links the design process to formalized experience and a software component characterization that allows both functional and non-functional aspects to be considered.ResultsThis method relies on the state-of-the-art strengths in the website design process, modeling dimensions, Model-Driven Engineering and the patterns approach. We propose an implementation of our method as a dedicated website which helps website design and provides a website analysis catalog and a software component analysis catalog.ConclusionOur analysis of the method’s use highlights that formalizing the steps of the design process helps designers, especially novice designers, to design a website; our analysis of the tool’s use highlights its efficiency for rapid website development and its use of the “website family” concept. The results are so very encouraging for both method and tool; both facilitate website design by reusing existing solutions and components.     

Dynamic decision models for staged software product line configuration

Software product line engineering practices offer desirable characteristics such as rapid product development, reduced time-to-market, and more affordable development costs as a result of systematic representation of the variabilities of a domain of discourse that leads to methodical reuse of software assets. The development lifecycle of a product line consists of two main phases: domain engineering, which deals with the understanding and formally modeling of the target domain, and application engineering that is concerned with the configuration of a product line into one concrete product based on the preferences and requirements of the stakeholders. The work presented in this paper focuses on the application engineering phase and builds both the theoretical and technological tools to assist the stakeholders in (a) understanding the complex interactions of the features of a product line; (b) eliciting the utility of each feature for the stakeholders and hence exposing the stakeholders’ otherwise implicit preferences in a way that they can more easily make decisions; and (c) dynamically building a decision model through interaction with the stakeholders and by considering the structural characteristics of software product line feature models, which will guide the stakeholders through the product configuration process. Initial exploratory empirical experiments that we have performed show that our proposed approach for helping stakeholders understand their feature preferences and its associated staged feature model configuration process is able to positively impact the quality of the end results of the application engineering process within the context of the limited number of participants. In addition, it has been observed that the offered tooling support is able to ease the staged feature model configuration process.     

基于UML与CCSP的产品配置方法

为了有效开发易维护可重用的产品配置模型以及实现配置问题的快速求解,提出了结合面向对象建模技术与条件约束满足问题理论的产品配置方法。给出了条件约束满足问题理论模型;提出了基于统一建模语言和条件约束满足问题的产品配置建模与求解方法;通过定义统一建模语言表示的产品配置概念模型与条件约束满足问题之间的映射规则集,建立了基于条件约束满足问题的产品配置模型。以某可配置医用监测器为应用实例,阐述了所提方法应用于配置模型构建与求解的可行性和有效性。     

Model-based incremental conformance checking to enable interactive product configuration

ContextModel-based product line engineering (PLE) is a paradigm that can enable automated product configuration of large-scale software systems, in which models are used as an abstract specification of commonalities and variabilities of products of a product line.ObjectiveIn the context of PLE, providing immediate feedback on the correctness of a manual configuration step to users has a practical impact on whether a configuration process with tool support can be successfully adopted in practice.MethodIn an existing work, a UML-based variability modeling methodology named as SimPL and an interactive configuration process was proposed. Based on the existing work, we propose an automated, incremental and efficient conformance checking approach to ensure that the manual configuration of a variation point conforms to a set of pre-defined conformance rules specified in the Object Constraint Language (OCL). The proposed approach, named as Zen-CC, has been implemented as an integrated part of our product configuration and derivation tool: Zen-Configurator.ResultsThe performance and scalability of Zen-CC have been evaluated with a real-world case study. Results show that Zen-CC significantly outperformed two baseline engines in terms of performance. Besides, the performance of Zen-CC remains stable during the configuration of all the 10 products of the product line and its efficiency also remains un-impacted even with the growing product complexity, which is not the case for both of the baseline engines.ConclusionThe results suggest that Zen-CC performs practically well and is much more scalable than the two baseline engines and is scalable for configuring products with a larger number of variation points.     

Requirements for product derivation support: Results from a systematic literature review and an expert survey

ContextAn increasing number of publications in product line engineering address product derivation, i.e., the process of building products from reusable assets. Despite its importance, there is still no consensus regarding the requirements for product derivation support.ObjectiveOur aim is to identify and validate requirements for tool-supported product derivation.MethodWe identify the requirements through a systematic literature review and validate them with an expert survey.ResultsWe discuss the resulting requirements and provide implementation examples from existing product derivation approaches.ConclusionsWe conclude that key requirements are emerging in the research literature and are also considered relevant by experts in the field.     

Scalable prediction of non-functional properties in software product lines: Footprint and memory consumption

ContextA software product line is a family of related software products, typically created from a set of common assets. Users select features to derive a product that fulfills their needs. Users often expect a product to have specific non-functional properties, such as a small footprint or a bounded response time. Because a product line may have an exponential number of products with respect to its features, it is usually not feasible to generate and measure non-functional properties for each possible product.ObjectiveOur overall goal is to derive optimal products with respect to non-functional requirements by showing customers which features must be selected.MethodWe propose an approach to predict a product’s non-functional properties based on the product’s feature selection. We aggregate the influence of each selected feature on a non-functional property to predict a product’s properties. We generate and measure a small set of products and, by comparing measurements, we approximate each feature’s influence on the non-functional property in question. As a research method, we conducted controlled experiments and evaluated prediction accuracy for the non-functional properties footprint and main-memory consumption. But, in principle, our approach is applicable for all quantifiable non-functional properties.ResultsWith nine software product lines, we demonstrate that our approach predicts the footprint with an average accuracy of 94%, and an accuracy of over 99% on average if feature interactions are known. In a further series of experiments, we predicted main memory consumption of six customizable programs and achieved an accuracy of 89% on average.ConclusionOur experiments suggest that, with only few measurements, it is possible to accurately predict non-functional properties of products of a product line. Furthermore, we show how already little domain knowledge can improve predictions and discuss trade-offs between accuracy and required number of measurements. With this technique, we provide a basis for many reasoning and product-derivation approaches.     

Flexible feature binding in software product lines

A software product line (SPL) is a family of programs that share assets from a common code base. The programs of an SPL can be distinguished in terms of features, which represent units of program functionality that satisfy stakeholders’ requirements. The features of an SPL can be bound either statically at program compile time or dynamically at run time. Both binding times are used in SPL development and have different advantages. For example, dynamic binding provides high flexibility whereas static binding supports fine-grained customizability without any impact on performance (e.g., for use on embedded systems). However, contemporary techniques for implementing SPLs force a programmer to choose the binding time already when designing an SPL and to mix different implementation techniques when multiple binding times are needed. We present an approach that integrates static and dynamic feature binding seamlessly. It allows a programmer to implement an SPL once and to decide per feature at deployment time whether it should be bound statically or dynamically. Dynamic binding usually introduces an overhead regarding resource consumption and performance. We reduce this overhead by statically merging features that are used together into dynamic binding units. A program can be configured at run time by composing binding units on demand. We use feature models to ensure that only valid feature combinations can be selected at compile and at run time. We provide a compiler and evaluate our approach on the basis of two non-trivial SPLs.     

SimPL: A product-line modeling methodology for families of integrated control systems

ContextIntegrated control systems (ICSs) are heterogeneous systems where software and hardware components are integrated to control and monitor physical devices and processes. A family of ICSs share the same software code base, which is configured differently for each product to form a unique installation. Due to the complexity of ICSs and inadequate automation support, product configuration in this context is typically error-prone and costly.ObjectiveAs a first step to overcome these challenges, we propose a UML-based product-line modeling methodology that provides a foundation for semi-automated product configuration in the specific context of ICSs.MethodWe performed a comprehensive domain analysis to identify characteristics of ICS families, and their configuration challenges. Based on this, we formulated the characteristics of an adequate configuration solution, and derived from them a set of modeling requirements for a model-based solution to configuration. The SimPL methodology is proposed to fulfill these requirements.ResultsTo evaluate the ability of SimPL to fulfill the modeling requirements, we applied it to a large-scale industrial case study. Our experience with the case study shows that SimPL is adequate to provide a model of the product family that meets the modeling requirements. Further evaluation is still required to assess the applicability and scalability of SimPL in practice. Doing this requires conducting field studies with human subjects and is left for future work.ConclusionWe conclude that configuration in ICSs requires better automation support, and UML-based approaches to product family modeling can be tailored to provide the required foundation.     

Specification and automated validation of staged reconfiguration processes for dynamic software product lines

Dynamic software product lines (DSPLs) propose elaborated design and implementation principles for engineering highly configurable runtime-adaptive systems in a sustainable and feature-oriented way. For this, DSPLs add to classical software product lines (SPL) the notions of (1) staged (pre-)configurations with dedicated binding times for each individual feature, and (2) continuous runtime reconfigurations of dynamic features throughout the entire product life cycle. Especially in the context of safety- and mission-critical systems, the design of reliable DSPLs requires capabilities for accurately specifying and validating arbitrary complex constraints among configuration parameters and/or respective reconfiguration options. Compared to classical SPL domain analysis which is usually based on Boolean constraint solving, DSPL validation, therefore, further requires capabilities for checking temporal properties of reconfiguration processes. In this article, we present a comprehensive approach for modeling and automatically verifying essential validity properties of staged reconfiguration processes with complex binding time constraints during DSPL domain engineering. The novel modeling concepts introduced are motivated by (re-)configuration constraints apparent in a real-world industrial case study from the automation engineering domain, which are not properly expressible and analyzable using state-of-the-art SPL domain modeling approaches. We present a prototypical tool implementation based on the model checker SPIN and present evaluation results obtained from our industrial case study, demonstrating the applicability of the approach.     

Utilizing architectural styles to enhance the adaptation support of middleware platforms

ContextModern middleware platforms provide the applications deployed on top of them with facilities for their adaptation. However, the level of adaptation support provided by the state-of-the-art middleware solutions is often limited to dynamically loading and off-loading of software components. Therefore, it is left to the application developers to handle the details of change such that the system’s consistency is not jeopardized.ObjectiveWe aim to change the status quo by providing the middleware facilities necessary to ensure the consistency of software after adaptation. We would like these facilities to be reusable across different applications, such that the middleware can streamline the process of achieving safe adaptation.MethodOur approach addresses the current shortcomings by utilizing the information encoded in a software system’s architectural style. This information drives the development of reusable adaptation patterns. The patterns specify both the exact sequence of changes and the time at which those changes need to occur. We use the patterns to provide advanced adaptation support on top of an existing architectural middleware platform.ResultsOur experience shows the feasibility of deriving detailed adaptation patterns for several architectural styles. Applying the middleware to adapt two real-world software systems shows the approach is effective in consistently adapting these systems without jeopardizing their consistency.ConclusionWe conclude the approach is effective in alleviating the application developers from the responsibility of managing the adaptation process at the application-level. Moreover, we believe this study provides the foundation for changing the way adaptation support is realized in middleware solutions.     

一种生产线架构中的工作流过程定义复用方法

针对工作流管理系统在实际应用中面临的过程定义低效、复杂的问题,借鉴软件复用的思想,提出了一种生产线架构下的工作流过程定义复用方法.该方法建立在领域业务本体和工作流模板这两类可复用资产之上,尝试建立特定领域工作流过程定义的复用机制,以提高过程定义的效率.着重探讨了可复用资产的构建、描述和检索等问题.介绍了基于复用的工作流过程定义方法,并开发了相应的实用工具以验证该方法的有效性.     

Facilitating the evolution of products in product line engineering by capturing and replaying configuration decisions

Software product lines rely on developing reusable artifacts and defining their variability in models to support and accelerate the derivation of individual products. A major challenge in product lines is the continuous evolution of both the reusable artifacts and derived products. Products that have been derived from a product line have to be updated regularly, e.g., after bugfixes or the development of new features. Changes to reusable artifacts and variability models have to be propagated to derived products. The aim of our research is to provide automated support for the evolution of products derived from product lines by capturing and replaying configuration decisions. Our PUPLE (Product Updates in Product Line Engineering) approach supports updating derived products after changes to the product line they have been derived from. It exploits the structure of variability models and uses change-tracking data to minimize user intervention. The paper first explores how different types of product line changes influence the derived products. It then presents extensions to our decision-oriented product line approach DOPLER to support product line evolution. We evaluate the feasibility of the PUPLE approach with evolution tasks that were performed by engineers of an industry partner on a product line of an Eclipse-based tool suite with six derived products. We conclude with lessons learned and limitations of our approach.     

Architectural evolution of FamiWare using cardinality-based feature models

ContextAmbient Intelligence systems domain is an outstanding example of modern systems that are in permanent evolution, as new devices, technologies or facilities are continuously appearing. This means it would be desirable to have a mechanism that helps with the propagation of evolution changes in deployed systems.ObjectiveWe present a software product line engineering process to manage the evolution of FamiWare, a family of middleware for ambient intelligence environments. This process drives the evolution of FamiWare middleware configurations using cardinality-based feature models, which are especially well suited to express the structural variability of ambient intelligence systems.MethodFamiWare uses cardinality-based feature models and clonable features to model the structural variability present in ambient intelligence systems, composed of a large variety of heterogeneous devices. Since the management evolution of configurations with clonable features is manually untreatable due to the high number of features, our process automates it and propagates changes made at feature level to the architectural components of the FamiWare middleware. This is a model driven development process as the evolution management, the propagation of evolution changes and the code generation are performed using some kind of model mappings and transformations. Concretely we present a variability modelling language to map the selection of features to the corresponding FamiWare middleware architectural components.ResultsOur process is able to manage the evolution of cardinality-based feature models with thousands of features, something which is not possible to tackle manually. Thanks to the use of the variability language and the automatic code generation it is possible to propagate and maintain a correspondence between the FamiWare architectural model and the code. The process is then able to calculate the architectural differences between the evolved configuration and the previous one. Checking these differences, our process helps to calculate the effort needed to perform the evolution changes in the customized products. To perform those tasks we have defined two operators, one to calculate the differences between two feature model configurations and another to create a new configuration from a previous one.ConclusionOur process automatically propagates the evolution changes of the middleware family into the existing configurations where the middleware is already deployed and also helps us to calculate the effort in performing the changes in every configuration. Finally, we validated our approach, demonstrating the functioning of the defined operators and showing that by using our tool we can generate evolved configurations for FamiWare with thousands of cloned features, for several case studies.     

一种形式化的组件化软件过程建模方法

为了解决当前软件过程重用方法中存在的问题,特别是由于缺乏对软件过程组件及其操作法则的精确定义所带来的重用中的低效率问题,介绍了一种形式化的组件化软件过程建模方法(componentized software process modeling,简称CSPM).CSPM提供了形式化定义可重用软件过程的机制,并且给出了将过程组件组合成过程模型的一系列操作法则.利用CSPM方法,能够以严格的方式对软件过程组件进行重用,并且有效地避免了传统非形式化建模方法中因歧义而有可能引起的潜在错误.CSPM还可以将对组装后的软件过程模型针对某些特定性质的验证问题转化成对其对应组件的一系列子验证问题,从而通过指数地减少需要搜索的状态空间规模,将原来在某些特定环境下不实用的验证问题简化成验证代价较小的一系列问题.