Arden Syntax:Fuzzy Arden Syntax

Introduction

The principal change of version 2.9 is the introduction of support for fuzzy logic. Fuzzy logic is a multi-valued logic that has gained use in formal decision-making because of its value in representing reasoning involving imprecision. Unlike the typical binary (true-false) logic that continues to be supported in this version of the Arden Syntax, fuzzy logic incorporates degrees of truth or set membership (Steimann F. On the use and usefulness of fuzzy sets in medical AI . Artif Intell Med 2001;21:131-7). Clinical practice guidelines and other forms of clinical knowledge representation may employ fuzzy logic, using linguistic variables such as "severe" and "somewhat" without necessarily formally defining them or providing an objective quantification. These changes in the Arden Syntax allow fuzzy logic to be formally represented, thus supporting the representation of clinical guidelines and clinical reasoning generally.

FAQ

• Question: On the example fuzzy set on page 35-36 (TwotoThree := fuzzy set (2, 0), (2, 1), (2, 1), (3, 1), (3, 0);). Why did (2, 1) come twice time?
  • Answer: The first fuzzy set on page 36 is this
    
    TwotoThree := fuzzy set (2, 0), (2, 1), (2, 1), (3, 1), (3,0);
    
    At point 2 there is a "discontinuity point" which means that if we approaching 2 from the left side we have the membership value 0, while approaching 2 from the right side we have the membership value 1. The question is which membership value is assigned to 2. The document contains the sentence "The first assignment is the value at that point, unless the second one appears twice.".
    
    This means in the above example (fuzzy set TwotoThree) the membership value at point 2 is 1, since the (2, 1) appears twice.
    If we adjust the fuzzy set to
    
    TwotoThree := fuzzy set (2, 0), (2, 1), (3, 1), (3,0);
    
    the membership value at the point 2 is 0.