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Re: Semantic vs XML Rules (was XRules: Mind your own businessr

• To: Waleed Abdulla <Waleed_Abdulla@x...>
• Subject: Re: Semantic vs XML Rules (was XRules: Mind your own businessrules)
• From: Bob Foster <bob@o...>
• Date: Thu, 17 Mar 2005 13:48:25 -0800
• Cc: 'Bill de hÓra' <bill.dehora@p...>,xml-dev@l...
• In-reply-to: <06d301c52b10$1acada20$6501a8c0@waleedxp2>
• References: <06d301c52b10$1acada20$6501a8c0@waleedxp2>
• User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041217

I'm no expert on this, but here is my limited understanding.

Semantic rules can be automatically composed, e.g., to support 
multi-rule inference or induction. Semantic rules are also fairly uniform:

   value-or-expression verb value-or-expression

Conditions can be combined with boolean operators and, or and not, and 
can be processed to make inferences (forward chaining) or inductions 
(backward chaining).

It's hard to compare that with XRules. Maybe "The latest draft 
specification document is available for download from this web site" but 
the link doesn't jump out at me. ;-}

 From the tutorial, XRules appear to be rather more ad hoc, both in the 
way they are expressed and in what they can do. It may be that 
everything that XRules does could be expressed as one or more rules of 
the form:

   If
     xpath-expression
   Then (one or more of the following)
     set xpath-node-expression to xpath-value-expression
     set xpath-variable to xpath-value-expression
     report xpath-value-expression

A simpler formulation might invite simple questions that I don't know 
how to answer from the examples. Like, if one context sets a parameter 
to one value and another context sets the parameter to a different 
value, if both contexts succeed, what value does the parameter have? If 
the answer is pick one, then it is very different than semantic 
processing, which can have the ability to pursue both values as 
independent sets of facts ("x" is "a" or "x" is "b") and even to 
calculate the likelihood that one or the other is true.

Suppose one rule establishes a value that causes another rule to succeed 
and it resets the value so that the first rule is invoked? Does the 
system cycle infinitely or does it reach a fixed point?

Is there an efficient algorithm for determining which rules must be 
(re)tested?

And so on. My ignorance is vast, but I invite tutilege, even if I don't 
always understand it. ;-}

Bob

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    • From: "Waleed Abdulla" <Waleed_Abdulla@x...>

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