Transactions on Aspect-Oriented Software Development I

The design structure matrix (DSM) methodology and the net option value (NOV) model have been used before to show how aspects can add value to a design. Following an in-depth analysis of that study, this paper demonstrates how aspects can be beneficial as well as detrimental. The structural transformations involved in aspect modularizations are carefully analyzed in the context of DSMs. This analysis exposes the unique reversion effect on dependencies that aspect modules are known for. To capture that effect within the NOV model, we extend its original set of six modular operators with an additional reversion operator. Using a design case study, its NOV worksheet and NOV experiments’ curves are presented to show a simulation of the evolutionary patterns of modules, including aspect modules. These patterns show how subtle dependencies, or the lack of them, bring down, or up, the value of an existing design. Based on the observations made in this case study, preliminary design guidelines for aspects are formulated.

Design patterns offer flexible solutions to common problems in software development. Recent studies have shown that several design patterns involve crosscutting concerns. Unfortunately, object-oriented (OO) abstractions are often not able to modularize those crosscutting concerns, which in turn compromise the system reusability and maintainability. Hence, it is important verifying whether aspect-oriented approaches support improved modularization of crosscutting concerns relative to design patterns. Ideally, quantitative studies should be performed to compare OO and aspect-oriented implementations of classical patterns with respect to fundamental software engineering attributes, such as coupling and cohesion. This paper presents a quantitative study that compares Java and AspectJ solutions for the 23 Gang-of-Four patterns. We have used stringent software attributes as the assessment criteria. We have found that most aspect-oriented solutions improve separation of pattern-related concerns, although only four aspect-oriented implementations have exhibited significant reuse. This paper also discusses the scalability of the analyzed solutions with respect to separation of concerns, and the determination of a predictive model for the modularization of design patterns with aspects.

An aspect-oriented design model consists of a set of aspect models and a primary model. Each aspect model describes a feature that crosscuts elements in the primary model. Aspect and primary models are composed to obtain an integrated design view. In this paper we describe a composition approach that utilizes a merging algorithm and composition directives. Composition directives are used when the default merging algorithm is known or expected to yield incorrect models. Our prototype tool supports default class diagram composition.

Generic categories of aspects are described, and their potential value is explained. For some categories, broad classes of syntactically identifiable temporal properties, such as safety, liveness, or existence properties, are guaranteed to hold for a system with any aspect of the category woven into it, if the property was true in the system without the aspect. Thus classes of properties preserved by the aspect are defined. Moreover, relatively simple verification techniques are shown to hold for some classes of temporal properties over systems augmented with some other categories of aspects. Verification of new properties added by the aspects is also considered. Each category is defined in terms of the semantic transformation it makes to the state graphs of underlying systems. A generic procedure to identify syntactically when an aspect belongs to a category is described and related to existing code analysis systems that use static code analysis and dataflow techniques. The definitions of categories, identification procedures, and lemmas about property classes provide the needed foundations that justify and motivate automatic code analysis modules to identify aspect categories. The categories enable simpler proofs of correctness than would otherwise be possible, and exploiting their characteristics can aid in software development.

CaesarJ is an aspect-oriented language which unifies aspects, classes and packages in a single powerful construct that helps to solve a set of different problems of both aspect-oriented and component-oriented programming. The paper gradually introduces the concepts of the language and illustrates them by showing how they can be used for noninvasive component refinement and integration, as well as for development of well modularized flexible aspects. In this way we demonstrate that the combination of aspect-oriented constructs for joinpoint interception with advanced modularization techniques like virtual classes and propagating mixin composition can open the path towards large-scale aspect components.

Security, networking and prefetching are typical examples of concerns which crosscut system-level C applications. While a careful design can help to address these concerns, they frequently become an issue at runtime, especially if avoiding server downtime is important. Vulnerabilities caused by buffer overflows and double-free bugs are frequently discovered after deployment, thus opening critical breaches in running applications. Performance issues also often arise at run time: in the case of Web caches, e.g., a prefetching strategy may be required to increase performance. Aspect-oriented programming is an appealing solution to solve these issues. However, none of the current dynamic aspect systems is expressive and efficient enough to support them properly in the context of C applications. Arachne is a new aspect system specifically designed to address these issues. Its aspect language allows aspects to be expressed concisely using a sequence construct for quantification over function calls and accesses through variable aliases. Arachne enables aspects to be woven “on the fly” in running legacy applications. We show how these abilities can be used to prevent security breaches, to modularize the replacement of network protocols by more efficient ones, and to introduce prefetching in Web caches. We present two formal semantics for Arachne: one which defines in abstract terms the main properties of the sequence construct, and a second one which enables reasoning about the actual implementation. Following a detailed presentation of Arachne’s implementation, we give performance evaluations showing that Arachne is fast enough to extend high-performance applications, such as the Squid Web cache.

In this paper, we contribute to the characterisation of a programming style specific to aspect-oriented programming. For this purpose, we present a collection of refactorings for aspect-oriented source code, comprising refactorings to enable extraction to aspects of crosscutting concerns from object-oriented legacy code, the subsequent tidying up of the extracted aspects and factoring out of common code from similar aspects to superaspects. The second group of refactorings is documented in detail. In addition, we propose some new aspect-oriented code smells, including one smell that is specific to aspect modules. We also propose a reinterpretation of some of the traditional object-oriented code smells in the light of aspect-orientation, to detect the presence of crosscutting concerns.

Research in the design of aspect-oriented programming languages requires a workbench that facilitates easy experimentation with new language features and implementation techniques. In particular, new features for AspectJ have been proposed that require extensions in many dimensions: syntax, type checking and code generation, as well as data flow and control flow analyses. The AspectBench Compiler (abc) is an implementation of such a workbench. The base version of abc implements the full AspectJ language. Its front end is built using the Polyglot framework, as a modular extension of the Java language. The use of Polyglot gives flexibility of syntax and type checking. The back end is built using the Soot framework, to give modular code generation and analyses. In this paper, we outline the design of abc, focusing mostly on how the design supports extensibility. We then provide a general overview of how to use abc to implement an extension. We illustrate the extension mechanisms of abc through a number of small, but nontrivial, examples. We then proceed to contrast the design goals of abc with those of the original AspectJ compiler, and how these different goals have led to different design decisions. Finally, we review a few examples of projects by others that extend abc in interesting ways.