that you can not be sure that one rule is applied before another rule and so on. If an equation can be applied to the term, it will always be applied before any rewrite rule. Maude's built-in search can look for unwanted states and show that no such states can be reached. Maude has the ability to control what rule applications should be attempted at each step using meta-programming, due to the reflective property or rewriting logic. Usage Maude has been used to validate security protocols and critical code. The Maude system has proved flaws in cryptography protocols by just specifying what the system can do, and by looking for unwanted situations (states or terms that should not be possible to reach) the protocol can be shown to contain bugs, not programming bugs but situations happen that are hard to predict just by walking down the "happy path" as most developers do. References Further reading Clavel, Durán, Eker, Lincoln, Martí-Oliet, Meseguer and Quesada, 1998. Maude as a Metalanguage, in Proc. 2nd International Workshop on Rewriting Logic and its Applications, Electronic Notes in Theoretical Computer Science 15, Elsevier. Martí-Oliet and José Meseguer, 2002. Rewriting Logic: Roadmap and Bibliography. Theoretical Computer Science 285(2):121-154. Martí-Oliet and José Meseguer, 1993-2000. Rewriting Logic as a Logical and Semantic Framework. Electronic Notes in Theoretical Computer Science 4, Elsevier. External links Maude homepage at University of Illinois at Urbana-Champaign; The Real-Time Maude Tool homepage developed by Peter Csaba Ölveczky; An introduction to Maude by Neal Harman, Swansea University (errata) The Policy And GOal based Distributed Architecture written in Maude by SRI International. Maude for Windows, the Maude installer for Windows, and Maude Development Tools, the Maude Eclipse plugin developed by the MOMENT project at Technical University of Valencia (Spain). Logic programming languages Extensible syntax programming languages Formal specification languages Term-rewriting programming languages SRI International software