The original source of confusion was that some variables do not begin with a
question mark (?) in the "simple" patterns. This might appear to allow a
variable to have two representations within the same rule if both a simple and
traditional pattern use a deftemplate. All variables might have a leading
marker, including those in simple patterns, which could have a different marker
such as a sharp sign (#). The helpful, question-mark convention for variables
dates back to Micro-planner in the 70's.
Rule and query LHS syntax should not be easily to confuse with algorithmic
language syntax. Such obscurity makes learning Jess more difficult. The
suggested syntax below "?e.occup", which would be difficult to parse, hides the
meaning. This could lose a significant advantage of rule-based systems: even
an untrained observer, such as a manager or sponsor, can look at the code and
become convinced that an approach is appropriate.
Bob Kirby
At 06:54 AM 6/19/2007, Ernest Friedman-Hill wrote:
>On Jun 19, 2007, at 2:07 AM, Wolfgang Laun wrote:
>
>>One other system I know of lets you write (adopting the Jess syntax)
>>
>>(defrule crossover
>>?e <- (side {?e.occup == FALSE}) ; or some way of saying "this"?
>>?w <- (side {?w.occup == TRUE})
>>?br <- (bridge {?br.occup == FALSE}
>>{?br.east == ?e}
>>{?br.west == ?w})
>>=>
>>(printout t ?br.name " " ?e.name " " ?w.name crlf)
>
>You have guessed (something very close to) the syntax that we're
>using in Jess 7.1 . I think the leading "?" won't be needed, and
>within a single pattern, you can leave off the fact reference and
>that will refer to the slot from the fact matching that pattern.
>
>
>---------------------------------------------------------
>Ernest Friedman-Hill
>Advanced Software Research Phone: (925) 294-2154
>Sandia National Labs FAX: (925) 294-2234
>PO Box 969, MS 9012 [EMAIL PROTECTED]
>Livermore, CA 94550 http://www.jessrules.com
>
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