From: mailbox@dmitry-kazakov.de   
      
   On Thu, 05 Jan 2006 22:49:23 +0100, Ernst Murnleitner wrote:   
      
   > 1) In the draft of iec 1131-7 there is the accumulation method defined   
   > in the rule base section and at another page it is in the definition of   
   > the output variable.   
   >   
   > I think it is a mistake there and it should be in the definition of the   
   > output variable?   
      
   Technically, to have accumulation method specified per rules block is more   
   general.   
      
   BUT the only feasible accumulation method is OR, so accumulation   
   specifications are superfluous anyway. In my compiler all accumulation   
   methods except OR are flagged as errors.   
      
   > 2) According to the iec 1131-7, a subcondition is not only   
   > variable IS set   
   > but also   
   > variable   
   >   
   > e.g. IF variable THEN ...   
   >   
   > How should the term (variable) be handled? Should variable be used as a   
   > membership value (range 0..1)?   
      
   The variable should be of Boolean type (the draft is quite shallow in all   
   concerning types.) So if X is Boolean, that is - it is nominal with the   
   domain set {false, true} - then   
      
      IF X THEN ...   
      
   is equivalent to   
      
      IF X = true THEN ...   
      
   In FCL terms, which for strange reasons does not have equality (+ with   
   membership function constants allowed in conditions), the above would be:   
      
      IF X is (true,1)(false,0) AND (true,1)(false,0) is X THEN ...   
      
   i.e. X is a subset of {true} and {true} is a subset of X.   
      
   --------------------   
   IMO FCL needs a good deal of reworking. It is inconsistent in many parts   
   and has a lot of silly limitations. Type system is not specified. Set   
   notation is quite perplexing. Syntax is awful, and so on.   
      
   --   
   Regards,   
   Dmitry A. Kazakov   
   http://www.dmitry-kazakov.de   
      
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