Frames sind parametrisierte Elemente zur Erzeugung von Programmen in einer beliebigen Zielprogrammiersprache. Ihre Handhabung ist einfach und schnell zu erlernen. Allerdings findet bei Verwendung von Frames eine “Verunreinigung” des Programmcodes, der als Basis für die Generatorentwicklung dient, mit Befehlen der Generatorsprache statt. Dies erschwert die Weiterverwendung der gewohnten Entwicklungsumgebung für die Zielprogrammiersprache. Eine eventuelle Weiterentwicklung der Programmbasis muss anschließend in Form von Frames erfolgen. Im Rahmen dieser Arbeit erfolgt die Beschreibung noninvasiver Frames, bei denen Informationen zur Position der Frames getrennt vom Programmcode aufbewahrt werden. Ihre Vermischung erfolgt in einem separaten Schritt zur Darstellung oder zur eigentlichen Codeerzeugung. Der Prozess der Generatorentwicklung auf der Basis noninvasiver Frames passt sich gut in die Prozesse von Merkmal-orientierter (FOSD) und Generativer Softwareentwicklung (GSE) ein, weil noninvasive Frames die automatisierte Prüfung aller mit dem Generator erzeugbaren Programme hinsichtlich Syntax und bestimmter semantischer Eigenschaften unterstützen und die Generierung durch Auswahl der gewünschten Programmeigenschaften ermöglichen. Die Machbarkeit der Entwicklung von Softwaregeneratoren mit noninvasiven Frames wird anhand zweier Fallstudien demonstriert.

Many organizations specialize in the development of families of software systems, called software product lines (SPLs), for one or more domains (e.g., automotive, telephony, health care). SPLs are commonly developed as a shared set of assets representing the common and variable aspects of an SPL, and individual products are constructed by assembling the right combinations of assets. The feature-oriented software development (FOSD) paradigm advocates the use of system features as the primary unit of commonality and variability among the products of an SPL. A feature represents a coherent and identifiable bundle of system functionality, such as call waiting in telephony and cruise control in an automobile. Furthermore, FOSD aims at feature-oriented artifacts (FOAs); that is, software-development artifacts that explicate features, so that a clear mapping is established between a feature and its representation in different artifacts. The thesis first identifies the problem of developing a suitable language for expressing feature-oriented models of the functional requirements of an SPL, and then presents the feature-oriented requirements modelling language (FORML) as a solution to this problem. FORML's notation is based on standard software-engineering notations (e.g., UML class and state-machine models, feature models) to ease adoption by practitioners, and has a precise syntax and semantics to enable analysis. The novelty of FORML is in adding feature-orientation to state-of-the-art requirements modelling approaches (e.g., KAOS), and in the systematic treatment of modelling evolutions of an SPL via enhancements to existing features. An existing feature can be enhanced by extending or modifying its requirements. Enhancements that modify a feature's requirements are called intended feature interactions. For example, the call waiting feature in telephony intentionally overrides the basic call service feature's treatment of incoming calls when the subscriber is already involved in a call. FORML prescribes different constructs for specifying different types of enhancements in state-machine models of requirements. Furthermore, unlike some prominent approaches (e.g., AHEAD, DFC), FORML's constructs for modelling intended feature interactions do not depend on the order in which features are composed; this can lead to savings in analysis costs, since only one rather than (possibly) multiple composition orders need to be analyzed. A well-known challenge in FOSD is managing feature interactions, which, informally defined, are ways in which different features can influence one another in defining the overall properties and behaviours of their combination. Some feature interactions are intended, as described above, while other feature interactions are unintended: for example, the cruise control and anti-lock braking system features of an automobile may have incompatible affects on the automobile's acceleration, which would make their combination inconsistent. Unintended feature interactions should be detected and resolved. To detect unintended interactions in models of feature behaviour, we must first define a taxonomy of feature interactions for the modelling language: that is, we must understand the different ways that feature interactions can manifest among features expressed in the language. The thesis presents a taxonomy of feature interactions for FORML that is an adaptation of existing taxonomies for operational models of feature behaviour. The novelty of the proposed taxonomy is that it presents a definition of behaviour modification that generalizes special cases found in the literature; and it enables feature-interaction analyses that report only unintended interactions, by excluding interactions caused by FORML's constructs for modelling intended feature interactions.

Feature-oriented software architecture is a way of organizing code around the features that the program provides instead of the program's objects and components. In the development of a feature-oriented software system, the developers, supplied with a set of features, select and organize features to construct the desired system. This approach, by better aligning the implementation of a system with the external view of users, is believed to have many potential benefits such as feature reuse and easy maintenance. However, there are challenges in the formal verification of feature-oriented systems: first, the product may grow very large and complicated. As a result, it's intractable to apply the traditional formal verification techniques such as model checking on such systems directly; second, since the number of feature-oriented products the developers can build is exponential in the number of features available, there may be redundant verification work if doing verification on each product. For example, developers may have shared specifications on different products built from the same set of features and hence doing verification on these features many times is really unnecessary. All these drive the need for modular verifications for feature-oriented architectures. Assume-guarantee reasoning as a modular verification technique is believed to be an effective solution. In this thesis, I compare two verification methods of this category on feature-oriented systems and analyze the results. Based on their pros and cons, I propose a new modular model checking method to accomplish verification for sequential feature compositions with cyclic connections between the features. This method first builds an abstract finite state machine, which summarizes the information related to checking the property/specification from the concrete feature design, and then applies a revised CTL model checker to decide whether the system design can preserve the property or not. Proofs of the soundness of my method are also given in this thesis.

Frames sind parametrisierte Elemente zur Erzeugung von Programmen in einer beliebigen Zielprogrammiersprache. Ihre Handhabung ist einfach und schnell zu erlernen. Allerdings findet bei Verwendung von Frames eine “Verunreinigung” des Programmcodes, der als Basis für die Generatorentwicklung dient, mit Befehlen der Generatorsprache statt. Dies erschwert die Weiterverwendung der gewohnten Entwicklungsumgebung für die Zielprogrammiersprache. Eine eventuelle Weiterentwicklung der Programmbasis muss anschließend in Form von Frames erfolgen. Im Rahmen dieser Arbeit erfolgt die Beschreibung noninvasiver Frames, bei denen Informationen zur Position der Frames getrennt vom Programmcode aufbewahrt werden. Ihre Vermischung erfolgt in einem separaten Schritt zur Darstellung oder zur eigentlichen Codeerzeugung. Der Prozess der Generatorentwicklung auf der Basis noninvasiver Frames passt sich gut in die Prozesse von Merkmal-orientierter (FOSD) und Generativer Softwareentwicklung (GSE) ein, weil noninvasive Frames die automatisierte Prüfung aller mit dem Generator erzeugbaren Programme hinsichtlich Syntax und bestimmter semantischer Eigenschaften unterstützen und die Generierung durch Auswahl der gewünschten Programmeigenschaften ermöglichen. Die Machbarkeit der Entwicklung von Softwaregeneratoren mit noninvasiven Frames wird anhand zweier Fallstudien demonstriert.

Modern business applications are getting increasingly distributed as multi-tenant software as a service (SaaS). This leads to new challenges in terms of quality assurance, because all customers are directly affected by software changes. The resulting problem is to proactively determinate evolutionary effects. Because SaaS applications are often realized in the sense of a software product line, this thesis examines ways of using feature models to face the mentioned problem. For this purpose, two approaches are analyzed: extended feature models with quality attributes annotated per feature and the analysis of structural aspects of feature models and corresponding concrete configurations. The presented attributed feature model approach measures the quality of concrete configurations to make configurations comparable according to specific quality goals. Criteria are elicited for when configurations can be compared to draw helpful conclusions. The structural approach focuses economic questions that are quality assurance related, such as identifying features that none of the tenants selected in their application configurations. Furthermore, three algorithms are presented that demonstrate the structural analysis approach to gather information relevant to quality assurance.

Modern business applications are getting increasingly distributed as multi-tenant software as a service (SaaS). This leads to new challenges in terms of quality assurance, because all customers are directly affected by software changes. The resulting problem is to proactively determinate evolutionary effects. Because SaaS applications are often realized in the sense of a software product line, this thesis examines ways of using feature models to face the mentioned problem. For this purpose, two approaches are analyzed: extended feature models with quality attributes annotated per feature and the analysis of structural aspects of feature models and corresponding concrete configurations. The presented attributed feature model approach measures the quality of concrete configurations to make configurations comparable according to specific quality goals. Criteria are elicited for when configurations can be compared to draw helpful conclusions. The structural approach focuses economic questions that are quality assurance related, such as identifying features that none of the tenants selected in their application configurations. Furthermore, three algorithms are presented that demonstrate the structural analysis approach to gather information relevant to quality assurance.