Learn how to apply the proven concept of use cases within the rising paradigm of aspect orientation to build robust and extensible software.

Ivar Jacobson, Ph.D., is “the father” of many technologies, including components and component architecture, use cases, modern business engineering, and the Rational Unified Process. He was one of the three amigos who originally developed the Unified Modeling Language. He is the principal author of five best-selling books on these methods and technologies, in addition to being the coauthor of the two leading books on the Unified Modeling Language. Ivar is a founder of Jaczone AB, where he and his daughter and cofounder, Agneta Jacobson, are developing a ground-breaking new product that includes intelligent agents to support software development. Ivar also founded Ivar Jacobson Consulting (IJC) with the goal of promoting good software development practices throughout teams worldwide.

Pan-Wei Ng, Ph.D., plays multiple roles within Ivar Jacobson Consulting (IJC). Pan-Wei defines and develops materials for best practices in architecture, use cases, iterative development, aspects, and the like. This work is often done alongside practitioners to ensure that the best practices developed are both relevant and practical. Pan-Wei also actively works with customer accounts to enable companies and project teams to adopt these best practices quickly and safely.

What Is Aspect-Oriented Programming?That you have picked up this book tells us that you are a member of the software development community: a tester, a developer, a project leader, a project manager, an architect, an analyst, or a member involved in one of the many other aspects of developing. We also know that you are someone who wants to improve the way you develop software. You want your system to be more maintainable, more extensible, more reusable, and if you are a project leader, you want your team to be more productive. You know that these goals are not always easy to achieve.Why is software development so difficult? One reason is that there are many things to watch out for. On the human side, you have to watch out for time, budget, resources, skills, and so forth. Frequently, as a team member, you have many taskssome of them beyond what you are paid for. You report to two different people and each expects 100 percent from you, so you must give 200 percent to your work. As the developer, you must understand the application, the domain, and the idiosyncrasies of the platform. When you design the system, you need to deal with and balance many difficult concerns: how the system meets its intended functionality, how it achieves performance and reliability, how it deals with platform specifics, and so forth. You may find that your codeyour classes, your operations, your proceduresmust perform many functions, which may lead to spaghetti code, an indication of poor design. So, you need to improve designimprove modularity and provide betterseparation of concerns.Just as each team member must be clearly focused on his or her work, each component, each class, each operation must be focused on what is its specific purpose.But there is a limit to what you can do with existing techniques. No matter how far you go, you find that many parts of your system have code fragments that have to do with logging, authorization, persistence, debugging, tracing, distribution, exception handling, and other such tasks. Sometimes, a sizeable portion of an operation or class has nothing to do with what it is supposed to do. Aspect-oriented programming (AOP) refers to such redundancy ascrosscutting concernsbecause you find these code fragments in many operations and classes in your systemtheycut acrossoperations and classes. Crosscutting concerns are not limited to the technical concerns such as authorization and persistence. They include system and application functionality, and you find that a change in functionality often results in changes in many classes too.AOP gives you the means to separate code that implements crosscutting concerns and modularize it intoaspects.Aspect-orientation provides the mechanism to compose crosscutting behaviors into the desired operations and classes during compile time and even during execution. The source code for your operations and classes can be free of crosscutting concerns and therefore easier to understand and maintain. What Is Aspect-Oriented Software Development?In order to progress beyond AOP, you need a holistic approach to developing software systems with aspects from requirements, to analysis and design, to implementation and test. This is aspect-oriented software development (AOSD).AOSD is about better modularity for the entire system, encompassing concerns of many different kindsbetter modularity for functional requirements, nonfunctional requirements, platform specifics, and so onand keeping them separate from each other. Keeping all concerns separate allows you to construct systems that have a more understandable structure and are easily configured and extended to meet the evolving needs of stakeholders.AOSD is not just AOP. It encompasses a whole range of techniques to help you achieve better modularity. These techniques include objec