Product line models are used to drive the generation of requirements for single systems in the product line. They are difficult to validate because they are large and complex. By modelling variability and dependency between requirements using propositional connectives, a logical expression can be developed for the model. Validation of the selection of requirements from the model can be achieved by satisfying the logical expression. This approach can be used to validate the model as a whole. A detailed worked example is presented, and the computational aspects of the approach are discussed.

Using First-Order Logic for Product Line Model Validation

A customizable approach to full lifecycle variability management

The feature model is a domain/product-line oriented requirements model based on hierarchical structure and explicit variability modeling, and has been adopted by several important software reuse methods. However, with respect to the problem of verification of constraints on features and verification of partially customized feature models, these methods tend to be semi-formal and offer little formal assistance. In this paper, we propose a propositional logic-based method for the verification of feature models at different binding times. The most important characteristic of this method is that it integrates the logical verification with binding times, which makes it can be used to verify any partially customized feature models at any binding time (except run-time). In this method, constraints on features are formalized by logical sentences. Thus, the verification of feature models is converted into satisfaction problems in the logic. With this formal method, verification problems such as the detection of inconsistent constraints or the detection of conflicting or unnecessary binding resolutions can be automatically revealed.

A Propositional Logic-Based Method for Verification of Feature Models

The derivation of system test cases for product families is difficult due to variability in the requirements, since each variation point multiplies the number of possible behaviors to be tested. This paper proposes an approach to develop domain test cases from use cases that contain variabilities and to derive application test cases from them. The basic idea to avoid combinatorial explosion is to preserve the variability in domain test cases. New strategies to capture variability in test cases are suggested, which in combination help dealing with all basic types of variability in a use case and in its relationships (e.g., <<include>>).

Software Product-Family Engineering

Over the last decades computer based tools have been introduced to facilitate systems engineering processes. There are computer based tools for assisting engineers in virtually every aspect of the systems engineering process from requirement elicitation and analysis, over functional analysis, synthesis, implementation and verification. It is not uncommon for a tool to provide many services covering more than one aspect of systems engineering. There exist numerous situations where information exchanges across tool boundaries are valuable, e.g., exchange of specifications between organisations using heterogeneous tool sets, exchange of specifications from legacy to modern tools, exchange of pecifications to tools that provide more advanced modelling or analysis capabilities than the originating tool or storage of specification data in a neutral format such that multiple tools can operate on the data. The focus in this thesis is on the analysis, design and implementation of a method and tool neutral information model for enabling systems engineering tool data exchange. The information model includes support for representation of requirements, system functional architecture and physical architecture, and verification and validation data. There is also support for definition of multiple system viewpoints, representation of system architecture, traceability information and version and configuration management. The applicability of the information model for data exchange hasbeen validated through implementation of tool interfaces to COTS and proprietary systems engineering tools, and exchange of real specifications in different scenarios. The results obtained from the validation activities indicate that systems engineering tool data exchange may decrease the time spent for exchanging specifications between partners developing complex systems and that the information model approach described in the thesis is a compelling alternative to tool specific interfaces.

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An approach to systems engineering tool data representation and exchange

Reuse and requirements engineering are very important for efficient and successful systems development. However there are many open issues for performing them well in practice, especially raise of requirements. We present a new approach to reusing requirements based on application families i.e. several systems in a given problem domain. In contrast to precious approaches, an application family model in our approach consists of a pool of requirements (linked in a lattice structure), a domain model and a set of discriminants (a special kind of requirement that differentiate one system from another). We focus on how to make an efficient and clean selection of the requirements for a new system from an application family model. We have developed a method for solving this problem and a prototypical tool for supporting it. The method and the prototype were successfully developed under a study contract for ESA (European Space Agency). We present a case study, where we generated commanding requirements for an individual mission from an application family model of commanding requirements for spacecraft control operating systems. As a consequence, we propose this approach for reusing requirements based an application families.

J. Wheadon

Papers

Reusing single system requirements from application family requirements