Practical Statecharts in C/C++

Reader JonKaye contributed this review of Reviewing Practical Statecharts in C/C++. He writes "Since I am not from the embedded system world, I was a bit apprehensive about approaching this book. While I can see that author Miro Samek has a directed target for his audience, I strongly feel that this book is a 'must read' for technical developers in all areas who want to improve their program design abilities or developers who want to understand the philosophy, use, and implementation of statecharts intimately." Read on for the rest. Practical Statecharts in C/C++: Quantum Programming for Embedded Systems author Miro Samek pages 389 publisher CMP Books rating 10/10 reviewer Jonathan Kaye ISBN 1578201101 summary Practical and methodologically sound approach to improving software design using statecharts

As the title indicates, this book brings the topic of statecharts from the realm of expensive design tools to the practical realm, illustrating its points with full examples and extensive commentary.

Essentially Samek postulates that the slow adoption by developers of best practices by statechart design is due to lack of understanding of the fundamental nature of statecharts and how it is perceived as requiring expensive tools to use well. Samek insightfully discusses how statecharts as a best practice embody "behavioral inheritance" as a fundamental design concept that stands as a peer alongside the conventional pillars of object-oriented programming, namely inheritance, encapsulation, and polymorphism.

The book is very technical and written in an academic style, with ample references to original sources as well as detailed code reviews and many reader exercises. I would caution anyone from approaching this book as a quick or light read. For me, it took a seriousness and good understanding of C and C++ to follow Samek's examples and achieve the "a-ha", which was always worth it in the end. The book contains full, working code to incorporate statecharts into my own work, implemented both in C and C++.

The two basic parts of the text are (1) an explanation of statecharts and their methodological implications, and (2) a description of how to apply statecharts as a data structure in real applications, namely embedded as control strategies for "active objects." In several places in the text, Samek makes an analogy between statechart (and active object) semantics and quantum mechanics. This parallel was an interesting philosophical argument, but didn't add much for me in terms of accepting his "quantum framework" as a best practice -- I was sold by his methodological arguments he had presented already.

Speaking from experience in writing a book about using statecharts to build simulations (www.FlashSim.com), I can say Samek is a visionary who extended my perception of statecharts several steps. I know I will be quoting from it and referring to it in my work to come. This book has earned a prominent place on my bookshelf, and I would heartily recommend it to any other developer who wants to create correct, verifiable, scaleable, and solid designs (which should be ALL developers!)

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Comments

what ever happened to Zone Logic?

[e4liberty]

Zone Logic is a nice combination of state charts and autononmous agent design. It was used in the 80s and early 90s for industrial automation, and was particularly good at recovery from hardware failures.

Real-time systems depend on sensors to report the state of the outside world. These sensors often fail, putting the system in an illogical state. Zone Logic offered a nice structured way to deal with this.

R. Roberts. Zone Logic: A Unique Method of Practical Artificial Intelligence. Radnor, PA, Compute! Books, 1989. citeseer

Real world examples.

[dsplat]

It would have been quite nice of the author to include some links that describe what a statechart is and why a C++ programmer should care.

I learned about state diagrams in college years ago. The examples that we used at the time were all the sorts of things that could be done as stand-alone projects. They typically involved parsing strings that had to match a description given by a state diagram. If you are building a lexical scanner by hand or a regular expression library, it's good stuff to know. However, I wondered how often I'd see it in the real world.

Well folks, this can be real world stuff if you apply it. It's all about retaining a state that summarizes inputs that you have seen so far. This is about communication between autonomous devices (or with a user). If nothing else, state information is useful in retaining position within a set of search results when a user is paging through them. It can be used in the session layer of a communication protocol to track handshaking. If you have to asynchronously do two things concurrently within your program, unless each of them involves completely separate transactions that are completely atomic, one or both can be modelled as state machines.

If you write GUI code where you have buttons being toggled, check boxes checked or fields filled, you have a state machine, whether you coded it or not.

If you are writing embedded systems, you don't need me to tell you that you are maintaining real time state information about the devices you are talking to.