Hidehiko Masuhara

Modeling Crosscutting in Aspect-Oriented Mechanisms

Modeling four aspect-oriented programming mechanisms shows the way in which each supports modular crosscutting. Comparing the models produces a clear three part characterization of what is required to support crosscutting structure: a common frame of reference that two (or more) programs can use to connect with each other and each provide their semantic contribution.

A compilation and optimization model for aspect-oriented programs

This paper presents a semantics-based compilation model for an aspect-oriented programming language based on its operational semantics. Using partial evaluation, the model can explain several issues in compilation processes, including how to find places in program text to insert aspect code and how to remove unnecessary run-time checks. It also illustrates optimization of calling-context sensitive pointcuts (cflow), implemented in real compilers.

Dataflow Pointcut in Aspect-Oriented Programming

A dataflow-based pointcut is proposed for aspect-oriented programming (AOP) languages. The pointcut specifies where aspects should be applied based on the origins of values. It is designed to be compatible with the other kinds of pointcuts in existing AOP languages. Primary application fields of the pointcut are the aspects in which flow of information is important, such as security. This paper presents the design of the pointcut with a web-application example, and its prototype implementation.

EventCJ: a context-oriented programming language with declarative event-based context transition

This paper proposes EventCJ, a context-oriented programming (COP) language that can modularly control layer activation based on user-defined events. In addition to defining context-specific behaviors by using existing COP constructs, the EventCJ programmer declares events to specify when and on which instance layer switching should happen, and layer transition rules to specify which layers should be activated/deactivated upon events. These constructs enable controlling layer activation on a per-instance basis, separately from a base program. We also demonstrate an approach to verify safety properties of layer transitions by using a model checker. With these advantages, EventCJ enables more modular descriptions of context-aware programs, especially when layer switching is triggered in many places of a program, or by activities external to the base program. We implemented a prototype EventCJ compiler with Eclipse IDE support.

Association aspects

We propose a linguistic mechanism for AspectJ-like languages that concisely associates aspect instances to object groups. The mechanism, which supports association aspects, extends the per-object aspects in AspectJ by allowing an aspect instance to be associated to a group of objects, and by providing a new pointcut primitive to specify aspect instances as execution contexts of advice. With association aspects, we can straightforwardly implement crosscutting concerns that have stateful behavior related to a particular group of objects. The new pointcut primitive can more flexibly specify aspect instances when compared against previous implicit mechanisms. The comparison of execution times between the programs with association aspects and the ones with regular AspectJ aspects revealed that the association aspects exhibited almost equivalent for the medium-sized configurations.

A Simple Extension of Java Language for Controllable Transparent Migration and Its Portable Implementation

A scheme has been developed that enables a Java program to be migrated across computers while preserving its execution state, such as the values of local variables and the dynamic extents of try-and-catch blocks. This scheme provides the programmer with flexible control of migration, including transparent migration. It is based on source-code-level transformation. The translator takes as input code a Java program written in a Java language extended with language constructs for migration, and outputs pure Java source code that uses JavaRMI. The translated code can run on any Java interpreter and can be compiled by any just-in-time compiler. We have measured some execution performance for several application programs, and found that the translated programs are only about 20% slower than the original programs. Because migration is completely controlled by using only three language constructs added to the Java language (go, undock and migratory), the programmer can write programs to be migrated easily and succinctly. Our system is available in the public domain.

Aspectual Caml: an aspect-oriented functional language

We propose an aspect-oriented programming (AOP) language called Aspectual Caml based on a strongly-typed functional language Objective Caml with two AOP mechanisms similar to those in AspectJ language. This paper describes the design and implementation issues of those AOP mechanisms that give us insights into the interaction between AOP features and common features in strongly-typed functional languages such as type inference, polymorphic types and curried functions. We implemented a prototype compiler of the language and used the language for separating crosscutting concerns in application programs, including for separating descriptions of a type system from compiler descriptions.

Event-specific software composition in context-oriented programming

Context-oriented programming (COP) introduces dedicated abstractions for the modularization and dynamic composition of crosscutting context-specific functionality. While existing COP languages offer constructs for control-flow specific composition, they do not yet consider the explicit representation of event-specific context-dependent behavior, for which we observe two distinguishing properties: First, context can affect several control flows. Second, events can establish new contexts asynchronously. In this paper, we propose new language constructs for event-specific composition and explicit context representation and introduce their implementation in JCop, our COP extension to Java.

Design and Partial Evaluation of Meta-Objects for a Concurrent Reflective Language

Customizable meta-objects are a powerful abstraction for extending language features and implementation mechanisms, but interpretive execution suffers from severe performance penalty. Some of this penalty can be reduced by applying partial evaluation to meta-interpreters, but partial evaluation of meta-objects in existing concurrent object-oriented languages is ineffective. This paper proposes a new meta-object design for our reflective language ABCL/R3. It yields meta-objects that can be optimized effectively using partial evaluation. The crux of the design is the separation of state-related operations from other operations, and this separation is accomplished by using reader/writer methods in our concurrent object-oriented language called Schematic. Our benchmark trials show that non-trivial programs with partially evaluated meta-objects run more than six times faster than ones that are interpreted by meta-objects. In addition, a partially evaluated program that uses a customized meta-object runs as efficiently as a program that is manually rewritten so as to have the same functionality without using meta-objects.

A fine-grained join point model for more reusable aspects

We propose a new join point model for aspect-oriented programming (AOP) languages. In most AOP languages including AspectJ, a join point is a time interval of an action in execution. While those languages are widely accepted, they have problems in aspects reusability, and awkwardness when designing advanced features such as tracematches. Our proposed join point model, namely the point-in-time join point model redefines join points as the moments both at the beginning and end of actions. Those finer-grained join points enable us to design AOP languages with better reusability and flexibility of aspects. In this paper, we designed an AspectJ-like language based on the point-in-time model. We also give a denotational semantics of a simplified language in a continuation passing style, and demonstrate that we can straightforwardly model advanced language features such as exception handling and cflow pointcuts.