Agile Modeling (AM) is a practice-based methodology for effective modeling and documentation of software-based systems.   Simply put, Agile Modeling (AM) is a collection of values, principles, and practices for modeling software that can be applied on a software development project in an effective and light-weight manner.  As you see in Figure 1 AM is meant to be tailored into other, full-fledged methodologies such as XP or RUP, enabling you to develop a software process which truly meets your needs.

Figure 1. AM enhances other software processes.

The values of AM, adopting and extending those of eXtreme Programming v1, are communication, simplicity, feedback, courage, and humility.  The keys to modeling success are to have effective communication between all project stakeholders, to strive to develop the simplest solution possible that meets all of your needs, to obtain feedback regarding your efforts often and early, to have the courage to make and stick to your decisions, and to have the humility to admit that you may not know everything, that others have value to add to your project efforts.

AM is based on a collection of principles, such as the importance of assuming simplicity when you are modeling and embracing change as you are working because requirements will change over time.  You should recognize that incremental change of your system over time enables agility and that you should strive to obtain rapid feedback on your work to ensure that it accurately reflects the needs of your project stakeholders.  You should model with a purpose, if you don't know why you are working on something or you don't know what the audience of the model/document actually requires then you shouldn't be working on it. Furthermore, you need multiple models in your intellectual toolkit to be effective.  A critical concept is that models are not necessarily documents, a realization that enables you travel light by discarding most of your models once they have fulfilled their purpose.  Agile modelers believe that content is more important than representation, that there are many ways you can model the same concept yet still get it right. To be an effective modeler you need to recognize that open and honest communication is often the best policy to follow to ensure effective teamwork.  Finally, a focus on quality work is important because nobody likes to produce sloppy work and that local adaptation of AM to meet the exact needs of your environment is important.

To model in an agile manner you will apply AM's practices as appropriate.   Fundamental practices include creating several models in parallel, applying the right artifact(s) for the situation, and iterating to another artifact to continue moving forward at a steady pace.  Modeling in small increments, and not attempting to create the magical "all encompassing model" from your ivory tower, is also fundamental to your success as an agile modeler.  Because models are only abstract representations of software, abstractions that may not be accurate, you should strive to prove it with code to show that your ideas actually work in practice and not just in theory  Active stakeholder participation is critical to the success of your modeling efforts because your project stakeholders know what they want and can provide you with the feedback that you require.  The principle of assume simplicity is a supported by the practices of creating simple content by focusing only on the aspects that you need to model and not attempting to creating a highly detailed model, depicting models simply via use of simple notations, and using the simplest tools to create your models.  You travel light by single sourcing information, discarding temporary models and updating models only when it hurts.  Communication is enabled by displaying models publicly, either on a wall or internal web site, through collective ownership of your project artifacts, through applying modeling standards, and by modeling with others.  Your development efforts are greatly enhanced when you apply patterns gently.  Because you often need to integrate with other systems, including legacy databases as well as web-based services, you will find that you need to formalize contract models with the owners of those systems. Read this article for a better understanding of how AM's practices fit together.

I would argue that AM is an agile approach to modeling, that at its core AM is simply a collection of practices that reflect the principles and values shared by many experienced software developers. With an Agile Model Driven Development (AMDD) (see Figure 2) approach you typically do just enough high-level modeling at the beginning of a project to understand the scope and potential architecture of the system, and then during development iterations you do modeling as part of your iteration planning activities and then take a just in time (JIT) model storming approach where you model for several minutes as a precursor to several hours of coding.

Figure 2. Agile Model Driven Development (AMDD).

Another way to look at Agile Modeling is as a collection of best practices, as you see in Figure 3.

Figure 3. The best practices of Agile Modeling.

My experience is that these practices can be applied to most software development projects, you don't have to be working on an project following an agile software process (such as XP) to take advantage of the approaches described by AM, although one of AM's goals is to explain how to model when following the XP approach. A project team doesn't need to apply all of the practices, principles, and values of AM to benefit from it -- I have always been a firm believer that you should tailor your software process to reflect the unique needs of your environment -- although it is my opinion that like XP you are much more likely to succeed if you do adopt all of AM.

Recommended Resources

		The Object Primer 3rd Edition: Agile Model Driven Development with UML 2 is an important reference book for agile modelers, describing how to develop 35 types of agile models including all 13 UML 2 diagrams.  Furthermore, this book describes the techniques of the Full Lifecycle Object Oriented Testing (FLOOT) methodology to give you the fundamental testing skills which you require to succeed at agile software development.  The book also shows how to move from your agile models to source code (Java examples are provided) as well as how to succeed at implementation techniques such as refactoring and test-driven development (TDD).  The Object Primer also includes a chapter overviewing the critical database development techniques (database refactoring, object/relational mapping, legacy analysis, and database access coding) from my award-winning Agile Database Techniques book.
		Agile Modeling: Effective Practices for Extreme Programming and the Unified Process is the seminal book describing how agile software developers approach modeling and documentation.  It describes principles and practices which you can tailor into your existing software process, such as XP, the Rational Unified Process (RUP), or the Agile Unified Process (AUP), to streamline your modeling and documentation efforts.  Modeling and documentation are important aspects of any software project, including agile projects, and this book describes in detail how to elicit requirements, architect, and then design your system in an agile manner.
		The Elements of UML 2.0 Style describes a collection of standards, conventions, and guidelines for creating effective UML diagrams. They are based on sound, proven software engineering principles that lead to diagrams that are easier to understand and work with.  These conventions exist as a collection of simple, concise guidelines that if applied consistently, represent an important first step in increasing your productivity as a modeler.  This book is oriented towards intermediate to advanced UML modelers, although there are numerous examples throughout the book it would not be a good way to learn the UML (instead, consider The Object Primer).  The book is a brief 188 pages long and is conveniently pocket-sized so it's easy to carry around.

Let Us Help

We actively work with clients around the world to improve their information technology (IT) practices, typically in the role of mentor/coach, team lead, or trainer.  A full description of what we do, and how to contact us, can be found at Scott W. Ambler + Associates.