AOSD Ontology 1.0 - Public Ontology of Aspect-Orientation

This report presents a Common Foundation for Aspect-Oriented Software Development. A Common Foundation is required to enable effective communication and to enable integration of activities within the Network of Excellence. This Common Foundation is realized by developing an ontology, i.e. the shared meaning of terms and concepts in the domain of AOSD. In the first part of this report, we describe the definitions of an initial set of common AOSD terms. There is general agreement on these definitions. In the second part, we describe the Common Foundation task in detail

The Reflex Sandbox : an experimentation environment for an aspect-oriented Kernel

Reflex es un núcleo versátil para la programación orientada aspectos en Java. Provee de las abstracciones básicas, estructurales y de comportamiento, que permiten implementar una variedad de técnicas orientadas a aspectos. Esta tesis estudia dos tópicos fundamentales. En primer lugar, el desarrollo formal, utilizando el lenguaje Haskell, de las construcciones fundamentales del modelo Reflex para reflexión parcial de comportamiento. Este desarrollo abarca el diseño de un lenguaje, llamado Kernel, el cual es una extensión reflexiva de un lenguaje orientado a objetos simple. La semántica operacional del lenguaje Kernel es presentada mediante una máquina de ejecución abstracta. El otro tópico fundamental que estudia esta tesis es validar que el modelo de reflexión parcial de comportamiento es suficientemente expresivo para proveer de semántica a un subconjunto del lenguaje AspectJ. Con este fin, se desarrolló el Reflex Sandbox: un ambiente de experimentación en Haskell para el modelo Reflex. Tanto el desarrollo formal del modelo de reflexión parcial de comportamiento como la validación del soporte de AspectJ, son estudiados en el contexto del Reflex Sandbox. La validación abarca la definición de un lenguaje orientado a aspectos que caracteriza el enfoque de AspectJ a la programación orientada a aspectos, así como la definición de su máquina de ejecución abstracta. También se presenta un compilador que transforma programas escritos en este lenguaje al lenguaje Kernel. Este proceso de compilación provee los fundamentos para entender como dicha transformación puede ser realizada. El proceso de compilación también fue implementado en Java, pero transformando programas AspectJ a programas Reflex. También se presentan mediciones preliminares del desempeño de un programa compilado y ejecutado en Reflex y un programa compilado, y ejecutado con el compilador AspectJ

First-class Compositions - Defining and composing object and aspect compositions with first-class operators

A considerable amount of research, especially within the OO and AOSD communities, has focused on understanding the potential and limitations of various composition techniques. This has led to a large number of proposals for alternative composition techniques, including many variations of message dispatch, inheritance, and aspect mechanisms. This paper makes the case that there is no single perfect composition technique that suits every situation, since different techniques incur different trade-offs. The proper composition technique to use depends on the particular design problem and its requirements (e.g., with respect to adaptability, reusability, understandability, robustness, etc. of the various elements of the design). However, most programming languages limit the available composition techniques to a very few. To address this, we propose a novel composition model, called Co-op. The model provides dedicated abstractions that can be used to express a wide variety of object composition techniques ("composition operators''). Examples include various forms of inheritance, delegation, and aspects. The proposed model unifies objects (with encapsulated state and a message interface) and composition operators; composition operators are specified as first-class citizens. Multiple composition operators can be combined within the same application, and composition operators can even be used to compose new composition operators from existing ones. This opens new possibilities for developing domain-specific composition operators, taxonomies of composition operators, and for reuse and refinement of composition operators. To validate and experiment with the proposed model, we have designed and implemented a simple language, Co-op/I, that we also use in this paper to show concrete examples

On Language Processors and Software Maintenance

This work investigates declarative transformation tools in the context of software maintenance. Besides maintenance of the language specification, evolution of a software language requires the adaptation of the software written in that language as well as the adaptation of the software that transforms software written in the evolving language. This co-evolution is studied to derive automatic adaptations of artefacts from adaptations of the language specification. Furthermore, AOP for Prolog is introduced to improve maintainability of language specifications and derived tools.Die Arbeit unterstützt deklarative Transformationswerkzeuge im Kontext der Softwarewartung. Neben der Wartung der Sprachbeschreibung erfordert die Evolution einer Sprache sowohl die Anpassung der Software, die in dieser Sprache geschrieben ist als auch die Anpassung der Software, die diese Software transformiert. Diese Koevolution wird untersucht, um automatische Anpassungen von Artefakten von Anpassungen der Sprachbeschreibungen abzuleiten. Weiterhin wird AOP für Prolog eingeführt, um die Wartbarkeit von Sprachbeschreibungen und den daraus abgeleiteten Werkzeugen zu erhöhen

Un interpréteur extensible pour le prototypage des langages d'aspects

The value of using different (possibly domain-specific) aspect languages to deal with a variety of crosscutting concerns in the development of complex software systems is well recognized. One should be able to use several of these languages together in a single program. However, on the one hand, developing a new Domain-Specific Aspect Language (DSAL) in order to capture all common programming patterns of the domain takes a lot of time, and on the other hand, the designer of a new language should manage the interactions with the other languages when they are used together. In this thesis, we introduce support for rapid prototyping and composing aspect languages based on interpreters. We start from a base interpreter of a subset of Java and we analyze and present a solution for its modular extension to support AOP based on a common semantics aspect base defined once and for all. The extension, called the aspect interpreter, implements a common aspect mechanism and leaves holes to be defined when developing concrete languages. The power of this approach is that the aspect languages are directly implemented from their operational semantics. This is illustrated by implementing a lightweight version of AspectJ. To apply the same approach and the same architecture to full Java without changing its interpreter (JVM), we reuse AspectJ to perform a first step of static weaving, which we complement by a second step of dynamic weaving, implemented through a thin interpretation layer. This can be seen as an interesting example of reconciling interpreters and compilers. We validate our approach by describing prototypes for AspectJ, EAOP, COOL and a couple of other DSALs and demonstrating the openness of our AspectJ implementation with two extensions, one dealing with dynamic scheduling of aspects and another with alternative pointcut semantics. Different aspect languages implemented with our framework can be easily composed. Moreover, we provide support for customizing this composition.L'intérêt de l'utilisation de différents langages d'aspects pour faire face à une variété de préoccupations transverses dans le développement de systèmes logiciels complexes est reconnu. Il faudrait être capable d'utiliser plusieurs de ces langages dans un seul logiciel donné. Cependant, d'une part la phase de développement d'un nouveau langage dédié capturant tous les patrons de programmation du domaine prend beaucoup de temps et, d'autre part, le concepteur doit gérer les interactions avec les autres langages quand ils sont utilisés simultanément. Dans cette thèse, nous introduisons un support pour le prototypage rapide et la composition des langages d'aspects, basé sur des interpréteurs. Nous partons d'un interpréteur d'un sous-ensemble de Java en étudiant et en définissant son extension modulaire afin de supporter la programmation par aspects en se basant sur une sémantique d'aspects partagée. Dans l'interpréteur d'aspects, nous avons implémenté des mécanismes communs aux langages d'aspects en laissant des trous à définir pour implémenter des langages d'aspects concrets. La puissance de cette approche est de permettre d'implémenter directement les langages à partir de leur sémantique. L'approche est validée par l'implémentation d'une version légère d'AspectJ. Pour appliquer la même approche et la même architecture à Java sans modifier son interpréteur (JVM), nous réutilisons AspectJ pour effectuer une première étape de tissage statique, qui est complétée par une deuxième étape de tissage dynamique, implémentée par une mince couche d'interprétation. C'est un exemple montrant l'intérêt qu'il peut y avoir à concilier interprétation et compilation. Des prototypes pour AspectJ, EAOP, COOL et des langages dédiés simples, valident notre approche. Nous montrons le caractère ouvert de notre implémentation d'AspectJ en décrivant deux extensions: la première permet l'ordonnancement dynamique des aspects, la deuxième propose des sémantiques alternatives pour les points de coupe. Les langages d'aspects implémentés avec notre approche peuvent être facilement composés. En outre, cette composition peut être personnalisée

Aspect-Oriented State Machines

UML state machines are a widely used language for modeling software behavior. They are considered to be simple and intuitively comprehensible, and are hence one of the most popular languages for modeling reactive components. However, this seeming ease to use vanishes rapidly as soon as the complexity of the system to model increases. In fact, even state machines modeling ``almost trivial'' behavior may get rather hard to understand and error-prone. In particular, synchronization of parallel regions and history-based features are often difficult to model in UML state machines. We therefore propose High-Level Aspect (HiLA), a new, aspect-oriented extension of UML state machines, which can improve the modularity, thus the comprehensibility and reusability of UML state machines considerably. Aspects are used to define additional or alternative system behaviors at certain ``interesting'' points of time in the execution of the state machine, and achieve a high degree of separation of concerns. The distinguishing feature of HiLA w.r.t. other approaches of aspect-oriented state machines is that HiLA aspects are defined on a high, i.e. semantic level as opposed to a low, i.e. syntactic level. This semantic approach makes \HiLA aspects often simpler and better comprehensible than aspects of syntactic approaches. The contributions of this thesis include 1) the abstract and the concrete syntax of HiLA, 2) the weaving algorithms showing how the (additional or alternative) behaviors, separately modeled in aspects, are composed with the base state machine, giving the complete behavior of the system, 3) a formal semantics for HiLA aspects to define how the aspects are activated and (after the execution) left. We also discuss what conflicts between HiLA aspects are possible and how to detect them. The practical applicability of HiLA is shown in a case study of a crisis management system

An Abstract Metamodel for Aspect Languages

AOP is widely accepted as a language concept to improve separation of concerns, but it has often been pointed out that an encompassing theory of aspect composition is as yet missing. We define an abstract metamodel in which we capture the elements that we believe are the typical aspect oriented programming concepts. Also, these elements are crucial to the understanding of the semantics of AOP language constructs. We intend the metamodel to be a first step towards modeling and comparing AOP languages, as well as a foundation to define the semantics of AOP languages

An Overview of Language Support for Modular Event-driven Programming

Nowadays, event processing is becoming the backbone of many applications. Therefore, it is necessary to provide suitable abstractions to properly modularize the concerns that appear in event-driven applications. We identify four categories of languages that support event-driven programming, and identify their shortcomings in achieving modularity in the implementation of applications. We propose gummy modules and their implementation in the GummyJ language as a solution. Gummy modules have well-defined event-based interfaces, and can have a primitive or a composite structure. Composite gummy modules are means to group a set of correlated event processing concerns and restrict the visibility of events among them. We provide an example usage of gummy modules, and discuss their event processing semantics

Resource-based Verification for Robust Composition of Aspects

Aspect Oriented Software Development has been proposed as a means to improve modularization of software in the presence of crosscutting concerns. Compared to object-oriented or procedural approaches, Aspect Oriented Programming (AOP) has not yet been applied in many industrial applications. In this thesis we investigate the application of AOP within an industrial context and propose a novel solution to the problem of behavioral conflicts between aspects. We report on our experience transferring an aspect-oriented solution to a company called Advanced Semi-conductor Material Lithography (ASML). We investigate the acceptance criteria for AOP in industry, based on two industrial cases studies. We present a process that includes quantification of the benefits of AOP and elicitation of key worries expressed by stakeholders. We conducted a controlled experiment to assess the advantages and disadvantages of an aspect-based approach using a tracing example. Twenty developers from ASML were requested to carry out five maintenance scenarios. This experiment has shown that, in case the tracing concern is implemented using an AOP implementation instead of a procedural language, the development effort is on average 6% reduced while the impact of errors is reduced by 77%, for maintaining code related to tracing. For a subset of the scenarios, the results were statistically significant on a confidence interval of 95%. The so-called aspect interference problem is one of the major concerns in introducing AOP. Aspects can be developed independently and behave correct in isolation. However, due to intended or unintended composition of aspects, undesired behavior can emerge. In this thesis we focus on behavioral conflicts between aspects at shared join points. These are illustrated by a realistic example based on crosscutting concerns from ASML. We present an approach for the detection of behavioral interference that is based on a novel abstraction of the behavior of aspects, using resources and operations. This abstraction enables the expression of behavior in a simple manner that is suitable for automated detection of interference among aspects. The approach employs a set of conflict detection rules that can be used to detect both generic conflicts as well as domain specific conflicts. Our approach is general for AOP languages, its application to one specific AOP language Composition Filters is also illustrated in this thesis. The application to Composition Filters demonstrates how the use of a declarative advice language can be exploited for automated conflict detection. We detail the analysis process and discuss what information is required from the aspect developer to be able perform the analysis. We also discuss when static analysis is insufficient for detecting behavioral conflicts. We present a run time extension aiming at detecting dynamic conflicts. We discuss optimizations for this run time approach, which exploits the static verification results. Finally, we propose three improvements to the Composition Filters model to support automated and manual reasoning even further. The first improvement separates what behavior is executed from when this behavior is executed. Secondly, we introduce atomic filters that can be used to build more complex filters. The semantics of these filters are well defined. Although this approach has clear benefits from an automated reasoning perspective, the introduction of atomic filters results in the definition of numerous filters for specifying more complex behavior. Therefore, we introduce a filter composition language that enables the declarative composition of (atomic) filters, such that composed filter behavior can be reused elsewhere