Access control in feature-oriented programming

In feature-oriented programming (FOP) a programmer decomposes a program in terms of features. Ideally, features are implemented modularly so that they can be developed in isolation. Access control mechanisms in the form of access or visibility modifiers are an important ingredient to attain feature modularity as they allow programmers to hide and expose internal details of a module’s implementation. But developers of contemporary feature-oriented languages have not considered access control mechanisms so far. The absence of a well-defined access control model for FOP breaks encapsulation of feature code and leads to unexpected program behaviors and inadvertent type errors. We raise awareness of this problem, propose three feature-oriented access modifiers, and present a corresponding access modifier model. We offer an implementation of the model on the basis of a fully-fledged feature-oriented compiler. Finally, by analyzing ten feature-oriented programs, we explore the potential of feature-oriented modifiers in FOP.     

基于STEP的特征模型及重构算法

随着CAX技术的发展,特征技术得到越来越多的重视,特征技术的使用,大幅度提高了产品的设计、制造、集成等过程的效率。目前,基于特征的CAD、CAM系统是市场的主流,CAPP是完全基于特征的应用系统。但是在STEP的众多应用协议中,涉及机械设计、制造、管理的应用协议有很多,但是这些应用协议基本上没有提供对特征的支持。AP224是较早支持特征的STEP应用协议,主     

Empirical assessment of two approaches for specifying software product line use case scenarios

Modularity benefits, including the independent maintenance and comprehension of individual modules, have been widely advocated. However, empirical assessments to investigate those benefits have mostly focused on source code, and thus, the relevance of modularity to earlier artifacts is still not so clear (such as requirements and design models). In this paper, we use a multimethod technique, including designed experiments, to empirically evaluate the benefits of modularity in the context of two approaches for specifying product line use case scenarios: PLUSS and MSVCM. The first uses an annotative approach for specifying variability, whereas the second relies on aspect-oriented constructs for separating common and variant scenario specifications. After evaluating these approaches through the specifications of several systems, we find out that MSVCM reduces feature scattering and improves scenario cohesion. These results suggest that evolving a product line specification using MSVCM requires only localized changes. On the other hand, the results of six experiments reveal that MSVCM requires more time to derive the product line specifications and, contrasting with the modularity results, reduces the time to evolve a product line specification only when the subjects have been well trained and are used to the task of evolving product line specifications.     

基于适应性构件模型的软件产品线设计和实现

在当前面向特征的软件产品线开发方法中,需求级的可变性分析、可变点表示以及面向应用的定制已经得到了较好的支持。但是,从需求级的定制和裁剪( 特征模型) 到实现级( 体系结构和构件) 的映射仍然存在许多困难。针对这一问题,文章提出了一种基于适应性构件模型的软件产品线开发方法。这种适应性构件模型引入基于特征的领域模型作为构件端口( 包括内部端口和外部端口) 的语义基础。另一方面, 适应性构件模型所具有的微体系结构使得面向特定应用的构件行为定制成为可能。为了实现构件级面向特征的定制, 构件内部负责内部和外部协作的控制中心与构件的计算逻辑被分离开来执行经定制后的构件行为协议和端口语义。构件协作和计算功能的分离使针对构件行为的面向应用的定制更加便利。这样,产品线应用开发中需求级的特征定制就可以映射为体系结构和构件级的结构和行为调整。     

面向特征的反射式实时应用系统领域模型研究

本文主要研究实时应用系统领域工程中领域模型规约描述的问题，即开展实时应用软件设计与开发的垂直复用研究。通过扩展FODA（Feature-Oriented Domain Analysis）方法，引入实时特征作为该领域的需求规约单元，并从语义的角度来认识实时特征及其领域需求组织方式，同时应用反射技术来增强领域需求规约的动态性，最终归结为将实时特征作为实时应用需求空间的一阶实体来认识和组织实时应用系统领域模型，以寻求今后对实时应用系统领域语义一致性和可演化性的逻辑表达。     

Dealing with feature interactions for prismatic parts in STEP-NC

Determining the precedence of machining features is a critical issue in feature-based process planning. It becomes more complex when geometric interaction occurs between machining features. STEP-NC, the extension of STEP (ISO 10303) standard developed for CNC controllers, is a feature-based data model. It represents all the geometric and topological product data minus feature interactions. In this paper, machining precedence of interactive and non-interactive STEP-NC features is discussed. Local and global precedence of machining features are defined on the basis of geometric constraints, such as geometric interaction of features and feature approach face and technological constraint such as access direction of the cutting tool. A software tool has been developed to visualize the STEP-NC part model and to generate the graphs of feature interaction and feature precedence. The output can be then used to augment the STEP-NC data in order to generate the optimal sequence of operations.     

An algebraic foundation for automatic feature-based program synthesis

Feature-Oriented Software Development provides a multitude of formalisms, methods, languages, and tools for building variable, customizable, and extensible software. Along different lines of research, different notions of a feature have been developed. Although these notions have similar goals, no common basis for evaluation, comparison, and integration exists. We present a feature algebra that captures the key ideas of feature orientation and that provides a common ground for current and future research in this field, on which also alternative options can be explored. Furthermore, our algebraic framework is meant to serve as a basis for the development of the technology of automatic feature-based program synthesis and architectural metaprogramming.     

An approach to identify design and manufacturing features from a data exchanged part model

Due to the large variety of CAD systems in the market, data exchange between different CAD systems is indispensable. Currently, data exchange standards such as STEP and IGES, etc. provide a unique approach for interfacing among different CAD platforms. Once the feature-based CAD model created in one CAD system is input into another via data exchange standards, many of the original features and the feature-related information may not exist any longer. The identification of the design features and their further decomposition into machining features for the downstream activities from a data exchanged part model is a bottleneck in integrated product and process design and development. In this paper, the feature panorama is succinctly articulated from the viewpoint of product design and manufacturing. To facilitate feature identification and extraction, a multiple-level feature taxonomy and hierarchy is proposed based on the characteristics of part geometry and topology entities. The relationships between the features and their geometric entities are established. A litany of algorithms for the identification of design and machining features are proposed. Besides, how to recognize the intersecting features or compound features based on the featureless chunks of geometry entities is critical and the issue is addressed in the paper. A multi-level compound feature representation and recognition approach are presented. Finally, case studies are used to illustrate the validity of the approach and algorithms proposed for the identification of the features from CAD part models in neutral format.     

Formal semantics,modular specification,and symbolic verification of product-line behaviour

Formal techniques for specifying and verifying Software Product Lines (SPL) are actively studied. While the foundations of this domain recently made significant progress with the introduction of Featured Transition Systems (FTSs) and associated algorithms, SPL model checking still faces the well-known state explosion problem. Moreover, there is a need for high-level specification languages usable in industry. We address the state explosion problem by applying the principles of symbolic model checking to FTS-based verification of SPLs. In order to specify properties on specific products only, we extend the temporal logic CTL with feature quantifiers. Next, we show how SPL behaviour can be specified with fSMV, a variant of SMV, the specification language of the industry-strength model checker NuSMV. fSMV is a feature-oriented extension of SMV originally introduced by Plath and Ryan. We prove that fSMV and FTSs are expressively equivalent. Finally, we connect these results to a NuSMV extension we developed for verifying SPLs against CTL properties.     

A template-based approach for the generation of abstractable and reducible models of featured networks

We investigate the relationship between symmetry reduction and inductive reasoning when applied to model checking networks of featured components. Popular reduction techniques for combatting state space explosion in model checking, like abstraction and symmetry reduction, can only be applied effectively when the natural symmetry of a system is not destroyed during specification. We introduce a property which ensures this is preserved, open symmetry. We describe a template-based approach for the construction of open symmetric Promela specifications of featured systems. For certain systems (safely featured parameterised systems) our generated specifications are suitable for conversion to abstract specifications representing any size of network. This enables feature interaction analysis to be carried out, via model checking and induction, for systems of any number of featured components. In addition, we show how, for any balanced network of components, by using a graphical representation of the features and the process communication structure, a group of permutations of the underlying state space of the generated specification can be determined easily. Due to the open symmetry of our Promela specifications, this group of permutations can be used directly for symmetry reduced model checking.The main contributions of this paper are an automatic method for developing open symmetric specifications which can be used for generic feature interaction analysis, and the novel application of symmetry detection and reduction in the context of model checking featured networks.We apply our techniques to a well known example of a featured network – an email system.     

Warm fusion in Stratego: A case study in generation of program transformation systems

Stratego is a domain-specific language for the specification of program transformation systems. The design of Stratego is based on the paradigm of rewriting strategies: user-definable programs in a little language of strategy operators determine where and in what order transformation rules are (automatically) applied to a program. The separation of rules and strategies supports modularity of specifications. Stratego also provides generic features for specification of program traversals. In this paper we present a case study of Stratego as applied to a non-trivial problem in program transformation. We demonstrate the use of Stratego in eliminating intermediate data structures from (also known as deforesting) functional programs via the warm fusion algorithm of Launchbury and Sheard. This algorithm has been specified in Stratego and embedded in a fully automatic transformation system for kernel Haskell. The entire system consists of about 2600 lines of specification code, which breaks down into 1850 lines for a general framework for Haskell transformation and 750 lines devoted to a highly modular, easily extensible specification of the warm fusion transformer itself. Its successful design and construction provides further evidence that programs generated from Stratego specifications are suitable for integration into real systems, and that rewriting strategies are a good paradigm for the implementation of such systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Feature interactions and formal specifications intelecommunications

The feature-interaction problem found in complex software systems that support telecommunications is reviewed. The relationship between feature interactions and formal specifications is examined. Several important ways telecommunications has evolved beyond plain old telephone service (POTS) are described. It is shown how many feature interactions can be eliminated by applying known techniques of formal specification. A glossary that explains telecommunications terms not defined in the text and acronyms used throughout the article is included     

The impact of requirements changes on specifications and state machines

Requirements change both during and after a phase of development for a variety of reasons, including error correction and feature changes. Requirements change management is one of the most complex and difficult problems to deal with in requirements elicitation and tracking. It is generally not understood how a specific change propagates through the specification and into the code. In this paper we capture requirements changes as series of atomic changes in specifications. Using a rigorous specification method called sequence‐based specification, we propose a set of algorithms for managing all possible atomic requirements changes. The algorithms have been formulated within an axiom system for sequence‐based specification and proven for correctness. They have also been implemented in a prototype tool with which users are able to push requirements changes through to changes in specifications, maintain old specifications over time and evolve them into new specifications with the least amount of human interaction and rework. The approach of utilizing state machines to model and manage requirements changes guarantees strong evidence about the correctness and completeness of the proposed theory that will lead to more reliable software in the presence of change, especially with embedded systems and safety‐critical systems. The solution described is general enough for adoption by software and system developers, and well suited for incremental development. Copyright © 2008 John Wiley & Sons, Ltd.     

A Functional Rephrasing of the Assumption/Commitment Specification Style

The assumption/commitment (also called rely/guarantee) style has been advocated for the specification of interactive components of distributed systems. It suggests the structuring of specifications into assumptions about the behavior of the component's environment and into commitments that are fulfilled by the component, provided the environment fulfills these assumptions. One of its motivations is to achieve modularity (also called compositionality) for state transition specifications of system components. Another reason for writing specifications in this format lies in proof rules that refer to this format. We define the assumption/commitment formats for functional system specifications. In particular, we work out a canonical decomposition of system specifications following the assumption/commitment format into safety and liveness aspects. We demonstrate the format of assumption/commitment specifications by a number of examples. Finally, we discuss the methodological significance of the assumption/commitment format in the stepwise development of specifications.     

Decision-making coordination and efficient reasoning techniques for feature-based configuration

Software Product Lines is a contemporary approach to software development that exploits the similarities and differences within a family of systems in a particular domain of interest in order to provide a common infrastructure for deriving members of this family in a timely fashion, with high-quality standards, and at lower costs.In Software Product Lines, feature-based product configuration is the process of selecting the desired features for a given software product from a repository of features called a feature model. This process is usually carried out collaboratively by people with distinct skills and interests called stakeholders. Collaboration benefits stakeholders by allowing them to directly intervene in the configuration process. However, collaboration also raises an important side effect, i.e., the need of stakeholders to cope with decision conflicts. Conflicts arise when decisions that are locally consistent cannot be applied globally because they violate one or more constraints in the feature model.Unfortunately, current product configuration systems are typically single-user-based in the sense that they do not provide means to coordinate concurrent decision-making on the feature model. As a consequence, configuration is carried out by a single person that is in charge of representing the interests of all stakeholders and managing decision conflicts on their own. This results in an error-prone and time-consuming process that requires past decisions to be revisited continuously either to correct misinterpreted stakeholder requirements or to handle decision conflicts. Yet another challenging issue related to configuration problems is the typically high computational cost of configuration algorithms. In fact, these algorithms frequently fall into the category of NP-hard and thus can become intractable in practice.In this paper, our goal is two-fold. First, we revisit our work on Collaborative Product Configuration (CPC) in which we proposed an approach to describe and validate collaborative configuration scenarios. We discuss how collaborative configuration can be described in terms of a workflow-like plan that safely guides stakeholders during the configuration process. Second, we propose a preliminary set of reasoning algorithms tailored to the feature modelling domain that can be used to provide automated support for product configuration. In addition, we compare empirically the performance of the proposed algorithms to that of a general-purpose solution. We hope that the insights provided in this paper will encourage other researchers to develop new algorithms in the near future.     

Using schedulers to test probabilistic distributed systems

Formal methods are one of the most important approaches to increasing the confidence in the correctness of software systems. A formal specification can be used as an oracle in testing since one can determine whether an observed behaviour is allowed by the specification. This is an important feature of formal testing: behaviours of the system observed in testing are compared with the specification and ideally this comparison is automated. In this paper we study a formal testing framework to deal with systems that interact with their environment at physically distributed interfaces, called ports, and where choices between different possibilities are probabilistically quantified. Building on previous work, we introduce two families of schedulers to resolve nondeterministic choices among different actions of the system. The first type of schedulers, which we call global schedulers, resolves nondeterministic choices by representing the environment as a single global scheduler. The second type, which we call localised schedulers, models the environment as a set of schedulers with there being one scheduler for each port. We formally define the application of schedulers to systems and provide and study different implementation relations in this setting.     

Feature selection for event discovery in social media: A comparative study

Microblog as one kind of typical social media has many research implications in social event discovery and social-media-based e-learning and collaborative learning. At present, researchers usually employ feature-based classification approaches to detect social events in microblogs. However, it is very common to get different results when different features are used in event discovery. Therefore, it has been a critical issue how to select appropriate features for event discovery in microblogs. In this paper, we analyze five different feature selection methods and present an improved method for selecting features for microblog-based event discovery. We compare all the methods on a real microblog dataset in terms of various metrics including precision, recall, and F-measure. And finally we discuss the best feature selection method for the event discovery in microblogs. To the best of our knowledge, there are no such comparative studies on feature selection for event discovery in social media, and this paper is expected to offer some useful references for the future research and applications on the event discovery in microblogs.     

CAD/CAPP集成的关键技术

该文提出了基于特征实体模型上的截面轮廓造型自动特征识别方法。这种方法探索了一条实现自动特征识别的新途径。还提出了基于特征名、形面名的多层次多方位的零件信息描述方法。实现了对复杂箱体类零件的加工特征自动识别与信息自动提取,从而实现了CAD/CAPP系统的信息自动传递。