[RuleML-all] Multiple Assertions and Avoiding Recursion with RuleML& NxBRE

Sun Nov 18 23:17:33 AST 2007

Hi Don, NxBRE Developers, and All,

The RuleML-2007 paper "Are Your Rules Online? Four Web Rule Essentials":
http://www.ruleml.org/talks/RuleEssentials-talk.ppt
http://www.cs.unb.ca/~boley/papers/RuleEssentials.pdf
explains (much of) these examples, valid w.r.t. the RuleML 0.91 XSDs:
http://www.ruleml.org/usecases/essentials

The above are, however, only examples for Derivation RuleML:
http://www.ruleml.org/modularization/#Model

The logic variables used in Derivation RuleML cannot be updated except
consistently specialized. E.g., in hornlogeq the conjunctive query
corresponding to ?x=0, ?x=1 fails, but ?x=?y, ?x=1 succeeds.

You can derive multiple atoms by using a conjunction in a rule
conclusion,
as allowed in some RuleML sublanguages. FOL RuleML even allows
disjunctions
in the conclusions of rules: http://www.ruleml.org/fol/#Disjunctions.
Because
of this, and to allow stripe skipping, we make the <And> vs. <Or>
distinction
explicit in the <head>.

Your example <head> would thus become:

	<head>
         <And>
		<Atom>
			<Rel>RelDerived 1</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 1</Ind>
		</Atom>
		<Atom>
			<Rel>RelDerived 2</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 2</Ind>
		</Atom>
         </And>
	</head>

With stripe skipping, your first rule would then become:

<Implies>
         <Atom>
            <Rel>RelBase</Rel>
            <Var>entity</Var>
            <Ind>BaseValue</Ind>
         </Atom>
         <And>
		<Atom>
			<Rel>RelDerived 1</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 1</Ind>
		</Atom>
		<Atom>
			<Rel>RelDerived 2</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 2</Ind>
		</Atom>
         </And>
</Implies>

Perhaps a NxBRE developer can clarify the update rule in "another
situation".

Regarding actions such as updates, please stay tuned to Reaction RuleML:
http://ibis.in.tum.de/research/ReactionRuleML
http://mail.ruleml.org/pipermail/reaction-tg (mailing list)

Best,
Harold

-----Original Message-----
From: ruleml-all-bounces at ruleml.org
[mailto:ruleml-all-bounces at ruleml.org] On Behalf Of dhuffkc at hotmail.com
Sent: November 16, 2007 12:01 PM
To: ruleml-all at ruleml.org
Subject: [RuleML-all] Multiple Assertions and Avoiding Recursion with
RuleML& NxBRE

Pardon the basic questions.  I am using the NxBRE .NET engine, but my
questions are primarily RuleML-related.  If there's a "RuleML by
Example" 
resource available or a better forum to post I'd love to know about it.

Can I assert multiple new facts for the same condition (multiple heads
for one body)?  Something like:

<Implies>
	<head>
		<Atom>
			<Rel>RelDerived 1</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 1</Ind>
		</Atom>
		<Atom>
			<Rel>RelDerived 2</Rel>
			<Var>entity</Var>
			<Ind>DerivedValue 2</Ind>
		</Atom>
	</head>
	<body>
		<Atom>
			<Rel>RelBase</Rel>
			<Var>entity</Var>
			<Ind>BaseValue</Ind>
		</Atom>
	</body>
</Implies>

In another situation, I am deriving a new fact, then have rules that
modify that fact.  I only want to apply the modified rules once, however
the second implication continues to run:

<!-- assert new fact based on value of existing fact --> <Implies>
	<Atom>
		<Rel>Rel1</Rel>
		<Var>entity</Var>
		<Var>v1</Var>
	</Atom>
	<Atom>
		<Rel>NewRel</Rel>
		<Var>entity</Var>
		<Ind uri="nxbre://expression">{var:v1}</Ind>
	</Atom>
</Implies>

<!-- if Rel2(entity,i2) AND NewRel(entity,newValue), modify new fact
NewRel(entity,newValue+1) only once -->
<Implies>
	<And>
		<Atom>
			<Rel>Rel2</Rel>
			<Var>entity</Var>
			<Ind>i2</Ind>
		</Atom>
		<Atom>
			<Rel>NewRel</Rel>
			<Var>entity</Var>
			<Var>newValue</Var>
		</Atom>
	</And>
	<Atom>
		<Rel>NewRel</Rel>
		<Var>entity</Var>
		<Ind uri="nxbre://expression">{var:newValue} + 1</Ind>
	</Atom>
</Implies>

This is probably clear as mud, but any assistance is appreciated.

Regards,

Don Huff 

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