Zugl.: Stuttgart, Univ., Diss., 2008.

With ubiquitous computing, autonomous cars, and cyber-physical systems (CPS), adaptive software becomes more and more important as computing is increasingly context-dependent. Role-based programming has been proposed to enable adaptive software design without the problem of scattering the context-dependent code. Adaptation is achieved by having objects play roles during runtime. With every role, the object's behavior is modified to adapt to the given context. In recent years, many role-based programming languages have been developed. While they greatly differ in the set of supported features, they all incur in large runtime overheads, resulting in inferior performance. The increased variability and expressiveness of the programming languages have a direct impact on the run-time and memory consumption. In this paper we provide a detailed analysis of state-of-the-art role-based programming languages, with emphasis on performance bottlenecks. We also provide insight on how to overcome these problems.

Role-based modeling has been proposed in 1977 by Charles W. Bachman, as a means to model complex and dynamic domains, because roles are able to capture both context-dependent and collaborative behavior of objects. Consequently, they were introduced in various fields of research ranging from data modeling via conceptual modeling through to programming languages. More importantly, because current software systems are characterized by increased complexity and context-dependence, there is a strong demand for new concepts beyond object-oriented design. Although mainstream modeling languages, i.e., Entity-Relationship Model, Unified Modeling Language, are good at capturing a system's structure, they lack ways to model the system's behavior, as it dynamically emerges through collaborating objects. In turn, roles are a natural concept capturing the behavior of participants in a collaboration. Moreover, roles permit the specification of interactions independent from the interacting objects. Similarly, more recent approaches use roles to capture context-dependent properties of objects. The notion of roles can help to tame the increased complexity and context-dependence. Despite all that, these years of research had almost no influence on current software development practice. To make things worse, until now there is no common understanding of roles in the research community and no approach fully incorporates both the context-dependent and the relational nature of roles. In this thesis, I will devise a formal model for a family of role-based modeling languages to capture the various notions of roles. Together with a software product line of Role Modeling Editors, this, in turn, enables the generation of a role-based language family for Role-based Software Infrastructures (RoSI).

Present-day software systems have to fulfill an increasing number of requirements rendering them more and more complex. Many systems need to anticipate changing contexts (self-adaptive systems) or need to adapt to changing business rules or requirements (self-optimizing systems). The challenge of 21th century software development will be to cope with these aspects. We believe that the role concept offers a simple way to adapt object-oriented programs to their changing contexts. In a role-based language, an object plays multiple roles during its lifetime. If the contexts are represented as first-class entities, they provide dynamic views to the object-oriented program, and if the context changes, the dynamic views can be switched easily, and the software system adapts automatically. However, the concepts of roles and dynamic contexts have been discussed for a long time in many areas of computer science. So far, their implementation in an existing object-oriented language requires a specific runtime environment. Also, classical object-oriented languages and their runtime systems are not able to cope with essential role-specific features, such as true delegation or dynamic binding of roles. As a solution, this work presents a simple implementation pattern for role-based objects that does not require a specific runtime system, SCROLL (SCala ROles Language). The implementation pattern is demonstrated on the basis of the Scala language. As technical support from Scala, the pattern requires dynamic mixins, compiler-translated function calls, and implicit conversions. The implementation details of the pattern are hidden in a Scala library and therefore transparent to Scala programmers. The SCROLL library supports roles embedded in structured contexts, so-called compartments. We show that they are specific, hierarchic runtime views, which enables hierarchic view-based programming for free in Scala. We also discuss how to apply the implementation pattern of SCROLL for other languages, in particular for behavioral modeling languages in MDSD. This discussion shows that the SCROLL pattern can be embedded into the generated code, so that it still is hidden to the developer, but does not require a specific runtime system. Using the pattern in model-driven code generation enables dynamic views for all kinds of modeling languages. And therefore, this paper shows a way how to realize dynamic views for all modeling languages in MDSD.

Role-based modeling has been proposed in 1977 by Charles W. Bachman, as a means to model complex and dynamic domains, because roles are able to capture both context-dependent and collaborative behavior of objects. Consequently, they were introduced in various fields of research ranging from data modeling via conceptual modeling through to programming languages. More importantly, because current software systems are characterized by increased complexity and context-dependence, there is a strong demand for new concepts beyond object-oriented design. Although mainstream modeling languages, i.e., Entity-Relationship Model, Unified Modeling Language, are good at capturing a system's structure, they lack ways to model the system's behavior, as it dynamically emerges through collaborating objects. In turn, roles are a natural concept capturing the behavior of participants in a collaboration. Moreover, roles permit the specification of interactions independent from the interacting objects. Similarly, more recent approaches use roles to capture context-dependent properties of objects. The notion of roles can help to tame the increased complexity and context-dependence. Despite all that, these years of research had almost no influence on current software development practice. To make things worse, until now there is no common understanding of roles in the research community and no approach fully incorporates both the context-dependent and the relational nature of roles. In this thesis, I will devise a formal model for a family of role-based modeling languages to capture the various notions of roles. Together with a software product line of Role Modeling Editors, this, in turn, enables the generation of a role-based language family for Role-based Software Infrastructures (RoSI).:I Review of Contemporary Role-based Languages 1 Introduction 1.1 Background 1.2 Motivation 1.3 Problem Definition 1.4 Outline 2 Nature of Roles 2.1 Running Example 2.2 Behavioral Nature 2.3 Relational Nature 2.4 Context-Dependent Nature 2.5 Constraints in Role-Based Languages 2.6 Classification of Roles 3 Systematic Literature Review 3.1 Method 3.2 Results 3.3 Discussion 4 Contemporary Role-Based Modeling Languages 4.1 Behavioral and Relational Modeling Languages 4.1.1 Lodwick 4.1.2 The Generic Role Model 4.1.3 Role-Based Metamodeling Language (RBML) 4.1.4 Role-Based Pattern Specification 4.1.5 Object-Role Modeling (ORM) 2 4.1.6 OntoUML 4.2 Context-Dependent Modeling Languages 4.2.1 Metamodel for Roles 4.2.2 E-CARGO Model 4.2.3 Data Context Interaction (DCI) 4.3 Combined Modeling Languages 4.3.1 Taming Agents and Objects (TAO) 4.3.2 Information Networking Model (INM) 4.3.3 Helena Approach 5 Contemporary Role-based Programming Languages 5.1 Behavioral Programming Languages 5.1.1 Chameleon 5.1.2 Java with Roles (JAWIRO) 5.1.3 Rava 5.1.4 JavaStage 5.2 Relational Programming Languages 5.2.1 Rumer 5.2.2 First Class Relationships 5.2.3 Relations 5.3 Context-Dependent Programming Languages 5.3.1 EpsilonJ and NextEJ 5.3.2 Role/Interaction/Communicative Action (RICA) 5.3.3 ObjectTeams/Java 5.3.4 PowerJava 5.3.5 Scala Roles 6 Comparison of Role-based Languages 6.1 Comparison of Role-Based Modeling Languages 6.2 Comparison of Role-Based Programming Languages 6.3 Results and Findings II Family of Role-Based Modeling Languages 7 Foundations of Role-Based Modeling Languages 7.1 Ontological Foundation 7.1.1 Metaproperties 7.1.2 Classifying Modeling Concepts 7.2 Graphical Notation 7.2.1 Model Level Notation 7.2.2 Graphical Modeling Constraints 7.2.3 Instance Level Notation 7.3 Formalization of Roles 7.3.1 Model Level 7.3.2 Instance Level 7.3.3 Constraint Level 7.4 Reintroducing Inheritance 7.4.1 Extending the Banking Application 7.4.2 Model Level Extensions 7.4.3 Instance Level Extensions 7.4.4 Constraint Level Extensions 7.5 Reference Implementation 7.5.1 Translation of Logical Formulae 7.5.2 Structure of the Reference Implementation 7.5.3 Specifying and Verifying Role Models 7.6 Full-Fledged Role Modeling Editor 7.6.1 Software Architecture 7.6.2 Illustrative Example 7.6.3 Additional Tool Support 8 Family of Role-Based Modeling Languages 8.1 Family of Metamodels for Role-Based Modeling Languages 8.1.1 Feature Model for Role-Based Languages 8.1.2 Feature Minimal Metamodel 8.1.3 Feature Complete Metamodel 8.1.4 Mapping Features to Variation Points 8.1.5 Implementation of the Metamodel Generator 8.2 First Family of Role Modeling Editors 8.2.1 Dynamic Feature Configuration 8.2.2 Architecture of the Dynamic Software Product Line 8.2.3 Applicability of the Language Family Within RoSI 9 Conclusion 9.1 Summary 9.2 Contributions 9.3 Comparison with Contemporary Role-Based Modeling Languages 9.4 Future Research

Role-based modeling has been proposed almost 40 years ago as a means to model complex and dynamic domains, because roles are able to capture both context-dependent and collaborative behavior of objects. Unfortunately, while several researchers have introduced the notion of roles to modeling and programming languages, only few have captured both the relational and the context-dependent nature of roles. In this work, we classify various proposals since 2000 and show the discontinuity and fragmentation of the whole research field. To overcome discontinuity, we propose a family of metamodels for role-based modeling languages. Each family member corresponds to a design decision captured in a feature model. In this way, it becomes feasible to generate a metamodel for each role-based approach. This allows for the combination and improvement of the different role-based modeling and programming languages and paves the way to reconcile the research field.

The concept of roles is a promising approach to cope with context dependency and adaptivity of modern software systems. While roles have been investigated in conceptual modeling, programming languages and multi-agent systems, they have been given little consideration within component-based systems. In this paper, we propose a hierarchical role-based approach for modeling relationships and collaborations between components. In particular, we consider the channel-based, exogenous coordination language Reo and discuss possible realizations of roles and related concepts. The static requirements on the binding of roles are modeled by rule sets expressed in many-sorted second-order logic and annotations on the Reo networks for role binding, context and collaborations, while Reo connectors are used to model the coordination of runtime role playing. The ideas presented in this paper may serve as a basis for the formalization and formal analysis of role-based software systems.

This work deals with the problem to find and rate a solution how to administrate access rights in web based applications that are flexible and offer a fine-grained allocation of rights. In particular the program phpGACL is analyzed and integrated into an example application to prove the feasibility of this system in principle. / Diese Arbeit beschäftigt sich mit der Lösungsfindung und -bewertung des Problems, Zugriffsrechte webbasierter Anwendungen flexibel zu administrieren und eine möglichst feinkörnige Rechtevergabe zu erlauben. Insbesondere das Programm phpGACL wird analysiert und in eine Beispielanwendung integriert um die prinzipielle Realisierbarkeit des System zu überprüfen.

Die rollenbasierte Modellierung ist ein aktueller Forschungszweig, welcher Verfahren für die Analyse und die Lehre benötigt. Zu diesem Zweck präsentiert die Arbeit eine Erweiterung des klassischen, objektorientierten CRC-Karten-Verfahrens um rollenbasierte Konzepte. Diese basiert auf grundlegenden Eigenschaften rollenbasierter Elemente, wie Rollen, Objekte und Kontexte, welche modular in das CRC-Karten- Verfahren eingebunden werden. Weiterhin soll anhand einer empirische Studie ermittelt werden, wie gut das rollenerweiterte R-CRC-Karten-Verfahren für die Aufgaben in Analyse und Lehre geeignet ist. Das R-CRC-Karten-Verfahren soll letztendlich eine effiziente Möglichkeit bieten, Problemstellungen rollenbasiert zu analysieren und rollenbasierte Konzepte in der Lehre zu vermitteln.

Die rollenbasierte Modellierung ist ein aktueller Forschungszweig, welcher Verfahren für die Analyse und die Lehre benötigt. Zu diesem Zweck präsentiert die Arbeit eine Erweiterung des klassischen, objektorientierten CRC-Karten-Verfahrens um rollenbasierte Konzepte. Diese basiert auf grundlegenden Eigenschaften rollenbasierter Elemente, wie Rollen, Objekte und Kontexte, welche modular in das CRC-Karten- Verfahren eingebunden werden. Weiterhin soll anhand einer empirische Studie ermittelt werden, wie gut das rollenerweiterte R-CRC-Karten-Verfahren für die Aufgaben in Analyse und Lehre geeignet ist. Das R-CRC-Karten-Verfahren soll letztendlich eine effiziente Möglichkeit bieten, Problemstellungen rollenbasiert zu analysieren und rollenbasierte Konzepte in der Lehre zu vermitteln.