The LNCS Journal Transactions on Aspect-Oriented Software Development is devoted to all facets of aspect-oriented software development (AOSD) techniques in the context of all phases of the software life cycle, from requirements and design to implementation, maintenance and evolution. The focus of the journal is on approaches for systematic identification, modularization, representation and composition of crosscutting concerns, i.e., the aspects, evaluation of such approaches and their impact on improving quality attributes of software systems.This book, the first volume in the Transactions on Aspect-Oriented Software Development series, presents nine revised papers that have been through a careful peer reviewing process by the journal's Editorial Board. The papers cover a wide range of topics from software design to implementation of aspect-oriented languages. The first four articles address various issues of aspect-oriented modeling at the design level; the following four articles discuss various programming language issues.  The final article in this volume describes a workbench for implementing aspect-oriented languages, so that easy experimentation with new language features and implementation techniques are possible.