This article describes the difficulties caused by crosscutting constraints and provides a description of the AO techniques that are being used to ameliorate the problem. Our goal is to encode important issues about the system being modeled in a clean and localized manner. A key feature of this approach is it provides a framework that uses software code generators to create new domain-specific weavers

The issues of code scattering and tangling, thus of achieving a better modularity for a system’s concerns, are addressed by the paradigm of aspect orientation. Aspect mining is a reverse engineering process that aims at finding crosscutting concerns in existing systems. This paper describes a technique based on determining methods that are called from many different places (and hence have a high fan-in) to identify candidate aspects in a number of open-source Java systems. The most interesting aspects identified are discussed in detail, which includes several concerns not previously discussed in the aspect-oriented literature. The results show that a significant number of aspects can be recognized using fan-in analysis, and that the technique is suitable for a high degree of automation. 1.

Most software systems are inflexible. Reconfiguring a system’s modules to add or to delete a feature requires substantial effort. This inflexibility increases the costs of building variants of a system, amongst other problems. New languages and tools that are being developed to provide additional support for separating concerns show promise to help address this problem. However, applying these mechanisms requires determining how to enable a feature to be separated from the codebase. In this paper, we investigate this problem through an exploratory study conducted in the context of two existing systems: gnu.regexp and jFTPd. The study consisted of applying three different separation of concern mechanisms—Hyper/J, TM AspectJ, TM and a lightweight, lexically-based approach—to separate features in the two packages. In this paper, we report on the study, providing contributions in two areas. First, we characterize the effect different mechanisms had on the structure of the codebase. Second, we characterize the restructuring process required to perform the separations. These characterizations can help researchers to elucidate how the mechanisms may be best used, tool developers to design support to aid the separation process, and early adopters to apply the techniques.

Determining the best method for evaluating the effectiveness of a new technology. Wouldn’t it be advantageous to know in advance that the use of AOP [3] for your next project would be successful? Unfortunately, developers and managers seldom have access to evidence assuring them that the benefits promised by a new technology, such as AOP, will be achieved if they adopt the technology. Instead, they must take a leap of faith, believ-ing the technology will help them overcome problems encountered previously.

personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee."

. A namespace is a mapping from labels to values. Most programming languages support different forms of namespaces, such as records, dictionaries, objects, environments, packages and even keyword-based parameters. Typically only a few of these notions are first-class, leading to arbitrary restrictions and limited abstraction power in the host language. Piccola is a small language that unifies various notions of namespaces as first-class forms, or extensible, immutable records. By making namespaces explicit, Piccola is easily able to express various abstractions that would normally require more heavyweight techniques, such as language extensions or meta-programming. 1 Introduction Virtually all programming languages support various notions of namespaces, or sets of bindings of labels to values. These include: . Interface. Objects have a set of named methods. . Scopes. Identifiers are bound in the enclosing static or dynamic scope. . Package. A package provides a set of name...

Aspect mining is a reverse engineering process that aims at finding crosscutting concerns in existing systems. This paper proposes an aspect mining approach based on determining methods that are called from many different places, and hence have a high fan-in, which can be seen as a symptom of crosscutting functionality. The approach is semi-automatic, and consists of three steps: metric calculation, method filtering, and call site analysis. Carrying out these steps is an interactive process supported by an Eclipse plug-in called FINT. Fan-in analysis has been applied to three open source Java systems, totaling around 200,000 lines of code. The most interesting concerns identified are discussed in detail, which includes several concerns not previously discussed in the aspect-oriented literature. The results show that a significant number of crosscutting concerns can be recognized using fan-in analysis, and each of the three steps can be supported by tools.

Abstract. Understanding a software system at source-code level requires understanding the different concerns that it addresses, which in turn requires a way to identify these concerns in the source code. Whereas some concerns are explicitly represented by program entities (like classes, methods and variables) and thus are easy to identify, crosscutting concerns are not captured by a single program entity but are scattered over many program entities and are tangled with the other concerns. Because of their crosscutting nature, such crosscutting concerns are difficult to identify, and reduce the understandability of the system as a whole. In this paper, we report on a combined experiment in which we try to identify crosscutting concerns in the JHotDraw framework automatically. We first apply three independently developed aspect mining techniques to JHotDraw and evaluate and compare their results. Based on this analysis, we present three interesting combinations of these three techniques, and show how these combinations provide a more complete coverage of the detected concerns as compared to the original techniques individually. Our results are a first step towards improving the understandability of a system that contains crosscutting concerns, and can be used as a basis for refactoring the identified crosscutting concerns into aspects. 1

Exception handling mechanisms are intended to help developers build robust systems. Although an exception handling mechanism provides a basis for structuring source code dealing with unusual situations, little information is available to help guide a developer in the appropriate application of the mechanism. In our experience, this lack of guidance leads to complex exception structures. In this paper, we reflect upon our experiences using the Java exception handling mechanism. Based on these experiences, we discuss two issues we believe underlie the difficulties encountered: exceptions are a global design problem, and exception sources are often difficult to predict in advance. We then describe a design approach, based on work by Litke for Ada programs, which we have used to simplify exception structure in existing Java programs.

Ever since their invention 30 years ago, checked exceptions have been a point of much discussion. On the one hand, they increase the robustness of soft ware by preventing the manifestation of unanticipated checked exceptions at run-time. On the other hand, they decrease the adaptability of software bec ause they must be propagated explicitly, and must often be handled even if they cannot be signalled. We show that these problems are caused by a conflict between the exceptional interface of a method and the principle of abstraction. We then solve this conflict by introducing anchored exception declarations, which allow the exceptional behaviour of a method to be declared relative to that of others. We present their formal semantics, along with the necessary rules for ensuring compile-time safety, and give a proof of correctness. We show that ancho red exception declarations do not violate the principle of information hiding when used properly, and provide a guideline for when to use them. We have implemented anchored exception declarations as an extension to the ClassicJava programming language, called Cappuccino.