StateWORKS Newsletter 2/05


  1. Welcome
  2. Moore or Mealy model: that's the question

1. Welcome

Our web site seems to develop into a source of information about state machines. We are getting questions which demonstrate the difficulties people have with basic definitions relating to control systems, finite state machines and executable specifications. I appreciate those questions as it is much better to ask a question than to hide ignorance in an unnecessary complex code.

To meet that demand I have decided to write this year some technical notes about basic topics in those domains. I hope it will help those persons who are potential candidates for using a more methodological way of designing control system software but need some support and encouragement. The topics are not as complex as they seem to be: often the complexity stems from confused terminology, misunderstandings, etc.

Today I start with the differences between Moore and Mealy models. By the way, the book "State machine in software" which is in preparation, will cover the entire spectrum more thoroughly and fully. We hope to get it published soon.

F. Wagner

2. Moore or Mealy model: that's the question

Moore and Mealy models are the basic two models of state machines as defined in the literature. To understand the differences between them the actions (outputs) must be defined and bound to state changes. The technical note " Moore or Mealy model" discusses both models and shows that the optimal solution is achieved when features of both models are used in a mixed model. Although the concepts of these two models are useful when performing certain theoretical studies, they are not so important these days for software developers, and StateWORKS makes the use of a mixed model easy and effective.

The examples discussed in the technical note are also available on our web-site. The examples may be opened and studied with SWStudio, including the free LE version.