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A must read for all system developers
on 18 July 2010
This is a different book. Where most books expound a single theme such as Agile, Lean, or Scrum, "Lean Architecture for Agile Software Development" paints on a much broader canvas: Working with the end user, end user's mental model, user requirements, system architecture, and right down to actual code.
This is neither a beginner's "how to do it in ten easy lessons" nor is it a design method. It is a book written for the mature professional by two authors whose long experience has given them a deep understanding of what really matters in practical programming.
At a first glance, many methodologies appear as mere fads, but Coplien and Bjørnvig see through the fads and build on their real worth to create a thought-provoking and eminently practical book.
Three random jottings from my first reading:
* Architecture: "No matter how we care to define it, software architecture should support the enterprise value stream even to the extent that the source code itself should reflect the end user's mental model of the world."
* Lean secret: "...unite specialists together in one room: everybody, all together, from early on."
* Form and functionality: "System architecture should reflect the end user's mental model of the world. The model has two parts: The first part relates to the user's thought process when viewing the screen, and to what the system is: its form. The second part relates to what end users do - interacting with the system - and how the system should respond to user input. This is the system functionality. We work with users to elicit and develop these models and to capture them in code as early as possible."
The authors claims that an end user should have a picture in his head that enables him to see the commands that are meaningful in a given situation and to understand what it will do for him. This picture, Jim calls it the end user's mental model, it will be reflected into the actual code in well-built systems.
A few years ago, this reviewer introduced a new programming paradigm that he called Data, Context, and Interaction (DCI). The main feature of this paradigm is that it splits the code into two distinct parts. One part specifies system state; the other part specifies system behavior. Coplien and Bjørnvig use this paradigm to fill in the gap between architecture and code execution. To quote from the book:
* Key building blocks of object-oriented design: "Objects, which are end users' conceptualization of things in their business world; Classes, which provide simple, encapsulated access to the data that represents business information; Roles, which interact in a use case to achieve some business goal."
This book is a MUST read for all who want to understand the true nature of systems development.