Towards an aspect weaving BPEL engine

This position paper proposes the use of dynamic aspects and the visitor design pattern to obtain a highly configurable and extensible BPEL engine. Using these two techniques, the core of this infrastructural software can be customised to meet new requirements and add features such as debugging, execution monitoring, or changing to another Web Service selection policy. Additionally, it can easily be extended to cope with customer-specific BPEL extensions. We propose the use of dynamic aspects not only on the engine itself but also on the workflow in order to tackle the problems of Web Service hot deployment and hot fixes to long running processes. In this way, composing aWeb Service "on-the-fly" means weaving its choreography interface into the workflow

FOAL 2004 Proceedings: Foundations of Aspect-Oriented Languages Workshop at AOSD 2004

Aspect-oriented programming is a paradigm in software engineering and FOAL logos courtesy of Luca Cardelli programming languages that promises better support for separation of concerns. The third Foundations of Aspect-Oriented Languages (FOAL) workshop was held at the Third International Conference on Aspect-Oriented Software Development in Lancaster, UK, on March 23, 2004. This workshop was designed to be a forum for research in formal foundations of aspect-oriented programming languages. The call for papers announced the areas of interest for FOAL as including, but not limited to: semantics of aspect-oriented languages, specification and verification for such languages, type systems, static analysis, theory of testing, theory of aspect composition, and theory of aspect translation (compilation) and rewriting. The call for papers welcomed all theoretical and foundational studies of foundations of aspect-oriented languages. The goals of this FOAL workshop were to: � Make progress on the foundations of aspect-oriented programming languages. � Exchange ideas about semantics and formal methods for aspect-oriented programming languages. � Foster interest within the programming language theory and types communities in aspect-oriented programming languages. � Foster interest within the formal methods community in aspect-oriented programming and the problems of reasoning about aspect-oriented programs. The papers at the workshop, which are included in the proceedings, were selected frompapers submitted by researchers worldwide. Due to time limitations at the workshop, not all of the submitted papers were selected for presentation. FOAL also welcomed an invited talk by James Riely (DePaul University), the abstract of which is included below. The workshop was organized by Gary T. Leavens (Iowa State University), Ralf L?ammel (CWI and Vrije Universiteit, Amsterdam), and Curtis Clifton (Iowa State University). The program committee was chaired by L?ammel and included L?ammel, Leavens, Clifton, Lodewijk Bergmans (University of Twente), John Tang Boyland (University of Wisconsin, Milwaukee), William R. Cook (University of Texas at Austin), Tzilla Elrad (Illinois Institute of Technology), Kathleen Fisher (AT&T Labs�Research), Radha Jagadeesan (DePaul University), Shmuel Katz (Technion�Israel Institute of Technology), Shriram Krishnamurthi (Brown University), Mira Mezini (Darmstadt University of Technology), Todd Millstein (University of California, Los Angeles), Benjamin C. Pierce (University of Pennsylvania), Henny Sipma (Stanford University), Mario S?udholt ( ?Ecole des Mines de Nantes), and David Walker (Princeton University). We thank the organizers of AOSD 2004 for hosting the workshop

An Efficient and Flexible Implementation of Aspect-Oriented Languages

Compilers for modern object-oriented programming languages generate code in a platform independent intermediate language preserving the concepts of the source language; for example, classes, fields, methods, and virtual or static dispatch can be directly identified within the intermediate code. To execute this intermediate code, state-of-the-art implementations of virtual machines perform just-in-time (JIT) compilation of the intermediate language; i.e., the virtual instructions in the intermediate code are compiled to native machine code at runtime. In this step, a declarative representation of source language concepts in the intermediate language facilitates highly efficient adaptive and speculative optimization of the running program which may not be possible otherwise. In contrast, constructs of aspect-oriented languages - which improve the separation of concerns - are commonly realized by compiling them to conventional intermediate language instructions or by driving transformations of the intermediate code, which is called weaving. This way the aspect-oriented constructs' semantics is not preserved in a declarative manner at the intermediate language level. This representational gap between aspect-oriented concepts in the source code and in the intermediate code hinders high performance optimizations and weakens features of software engineering processes like debugging support or the continuity property of incremental compilation: modifying an aspect in the source code potentially requires re-weaving multiple other modules. To leverage language implementation techniques for aspect-oriented languages, this thesis proposes the Aspect-Language Implementation Architecture (ALIA) which prescribes - amongst others - the existence of an intermediate representation preserving the aspect-oriented constructs of the source program. A central component of this architecture is an extensible and flexible meta-model of aspect-oriented concepts which acts as an interface between front-ends (usually a compiler) and back-ends (usually a virtual machine) of aspect-oriented language implementations. The architecture and the meta-model are embodied for Java-based aspect-oriented languages in the Framework for Implementing Aspect Languages (FIAL) respectively the Language-Independent Aspect Meta-Model (LIAM) which is part of the framework. FIAL generically implements the work flows required from an execution environment when executing aspects provided in terms of LIAM. In addition to the first-class intermediate representation of aspect-oriented concepts, ALIA - and the FIAL framework as its incarnation - treat the points of interaction between aspects and other modules - so-called join points - as being late-bound to an implementation. In analogy to the object-oriented terminology for late-bound methods, the join points are called virtual in ALIA. Together, the first-class representation of aspect-oriented concepts in the intermediate representation as well as treating join points as being virtual facilitate the implementation of new and effective optimizations for aspect-oriented programs. Three different instantiations of the FIAL framework are presented in this thesis, showcasing the feasibility of integrating language back-ends with different characteristics with the framework. One integration supports static aspect deployment and produces results similar to conventional aspect weavers; the woven code is executable on any standard Java virtual machine. Two instantiations are fully dynamic, where one is realized as a portable plug-in for standard Java virtual machines and the other one, called Steamloom^ALIA , is realized as a deep integration into a specific virtual machine, the Jikes Research Virtual Machine Alpern2005. While the latter instantiation is not portable, it exhibits an outstanding performance. Virtual join point dispatch is a generalization of virtual method dispatch. Thus, well established and elaborate optimization techniques from the field of virtual method dispatch are re-used with slight adaptations in Steamloom^ALIA . These optimizations for aspect-oriented concepts go beyond the generation of optimal bytecode. Especially strikingly, the power of such optimizations is shown in this thesis by the examples of the cflow dynamic property, which may be necessary to evaluate during virtual join point dispatch, and dynamic aspect deployment - i.e., the selective modification of specific join points' dispatch. In order to evaluate the optimization techniques developed in this thesis, a means for benchmarking has been developed in terms of macro-benchmarks; i.e., real-world applications are executed. These benchmarks show that for both concepts the implementation presented here is at least circa twice as fast as state-of-the-art implementations performing static optimizations of the generated bytecode; in many cases this thesis's optimizations even reach a speed-up of two orders of magnitude for the cflow implementation and even four orders of magnitude for the dynamic deployment. The intermediate representation in terms of LIAM models is general enough to express the constructs of multiple aspect-oriented languages. Therefore, optimizations of features common to different languages are available to applications written in all of them. To proof that the abstractions provided by LIAM are sufficient to act as intermediate language for multiple aspect-oriented source languages, an automated translation from source code to LIAM models has been realized for three very different and popular aspect-oriented languages: AspectJ, JAsCo and Compose*. In addition, the feasibility of translating from CaesarJ to LIAM models is shown by discussion. The use of an extensible meta-model as intermediate representation furthermore simplifies the definition of new aspect-oriented language concepts as is shown in terms of a tutorial-style example of designing a domain specific extension to the Java language in this thesis

ContextErlang: A language for distributed context-aware self-adaptive applications

Self-adaptive software modifies its behavior at run time to satisfy changing requirements in a dynamic environment. Context-oriented programming (COP) has been recently proposed as a specialized programming paradigm for context-aware and adaptive systems. COP mostly focuses on run time adaptation of the application’s behavior by supporting modular descriptions of behavioral variations. However, self-adaptive applications must satisfy additional requirements, such as distribution and concurrency, support for unforeseen changes and enforcement of correct behavior in the presence of dynamic change. Addressing these issues at the language level requires a holistic design that covers all aspects and takes into account the possibly cumbersome interaction of those features, for example concurrency and dynamic change. We present ContextErlang, a COP programming language in which adaptive abstractions are seamlessly integrated with distribution and concurrency. We define ContextErlang’s formal semantics, validated through an executable prototype, and we show how it supports formal proofs that the language design ensures satisfaction of certain safety requirements. We provide empirical evidence that ContextErlang is an effective solution through case studies and a performance assessment. We also show how the same design principles that lead to the development of ContextErlang can be followed to systematically design contextual extensions of other languages. A concrete example is presented concerning ContextScala

Co-Evolution of Source Code and the Build System: Impact on the Introduction of AOSD in Legacy Systems

Software is omnipresent in our daily lives. As users demand ever more advanced features, software systems have to keep on evolving. In practice, this means that software developers need to adapt the description of a software application. Such a description not only consists of source code written down in a programming language, as a lot of knowledge is hidden in lesser known software development artifacts, like the build system. As its name suggests, the build system is responsible for building an executable program, ready for use, from the source code. There are various indications that the evolution of source code is strongly related to that of the build system. When the source code changes, the build system has to co-evolve to safeguard the ability to build an executable program. A rigid build system on the other hand limits software developers. This phenomenon especially surfaces when drastic changes in the source code are coupled with an inflexible build system, as is the case for the introduction of AOSD technology in legacy systems. AOSD is a young software development approach which enables developers to structure and compose source code in a better way. Legacy systems are old software systems which are still mission-critical, but of which the source code and the build system are no longer fully understood, and which typically make use of old(-fashioned) technology. This PhD dissertation focuses on finding an explanation for this co-evolution of source code and the build system, and on finding developer support to grasp and manage this phenomenon. We postulate four "roots of co-evolution" which represent four different ways in which source code and the build system interact with each other. Based on these roots, we have developed tool and aspect language support to understand and manage co-evolution. The roots and the tool support have been validated in case studies, both in the context of co-evolution in general and of the introduction of AOSD technology in legacy systems. The dissertation experimentally shows that co-evolution indeed is a real problem, but that specific software development and aspect language support enables developers to deal with it

EFFICIENT RUNTIME SECURITY SYSTEM FOR DECENTRALISED DISTRIBUTED SYSTEMS

Distributed systems can be defined as systems that are scattered over geographical distances and provide different activities through communication, processing, data transfer and so on. Thus, increasing the cooperation, efficiency, and reliability to deal with users and data resources jointly. For this reason, distributed systems have been shown to be a promising infrastructure for most applications in the digital world. Despite their advantages, keeping these systems secure, is a complex task because of the unconventional nature of distributed systems which can produce many security problems like phishing, denial of services or eavesdropping. Therefore, adopting security and privacy policies in distributed systems will increase the trustworthiness between the users and these systems. However, adding or updating security is considered one of the most challenging concerns and this relies on various security vulnerabilities which existing in distributed systems. The most significant one is inserting or modifying a new security concern or even removing it according to the security status which may appear at runtime. Moreover, these problems will be exacerbated when the system adopts the multi-hop concept as a way to deal with transmitting and processing information. This can pose many significant security challenges especially if dealing with decentralized distributed systems and the security must be furnished as end-to-end. Unfortunately, existing solutions are insufficient to deal with these problems like CORBA which is considered a one-to-one relationship only, or DSAW which deals with end-to-end security but without taking into account the possibility of changing information sensitivity during runtime. This thesis provides a proposed mechanism for enforcing security policies and dealing with distributed systems’ security weakness in term of the software perspective. The proposed solution utilised Aspect-Oriented Programming (AOP), to address security concerns during compilation and running time. The proposed solution is based on a decentralized distributed system that adopts the multi-hop concept to deal with different requested tasks. The proposed system focused on how to achieve high accuracy, data integrity and high efficiency of the distributed system in real time. This is done through modularising the most efficient security solutions, Access Control and Cryptography, by using Aspect-Oriented Programming language. The experiments’ results show the proposed solution overcomes the shortage of the existing solutions by fully integrating with the decentralized distributed system to achieve dynamic, high cooperation, high performance and end-to-end holistic security

Aspect-oriented model-driven code generation approach for improving code reusability and maintainability

Software development teams always need methods that can help in producing high-quality software with reduced development effort and delivery time. Model-Driven Engineering (MDE) as well as Aspect-Oriented Software Development (AOSD) techniques help in reducing the delivery time, and also positively contribute to quality of the produced software. Through the use of AOSD techniques in combination with MDE, an integration of excellent abstraction mechanisms of MDE and capabilities of AOSD with regards to modularity and composition of concerns can be perceived, which is expected to enhance the positive effects of both techniques. To this end, different integration approaches have appeared in literature, but aspect-oriented code generation has advantages over the other approaches. Consequently, a number of aspect-oriented code generation approaches have been offered, but all such approaches lack several features mandatory to materialize a workable integration of aspect technologies in the context of MDE. To address these issues, this research was conducted to present an approach for aspect-oriented model-driven code generation, which focuses on elaborating the conceptual relationship between design models and the implementation code, and exploits the same to obtain aspect-oriented code that is more reusable and maintainable. The key outcomes of this research are the elaboration of the conceptual mappings between elements of visual design and constructs of the code, mapping of the visual models to implementation-specific text-based models, and a technique for generation of aspect-oriented code. The applicability of the proposed approach is shown by the use of case studies, whereas the quality of the approach is measured using reusability and maintainability metrics. A comparison of the proposed approach with existing approaches substantiates its efficacy in terms of reusability and maintainability of code, showing an outperformance of other approaches by the proposed approach against 78% of the employed quality metrics