If you want to check that there is no other WireCandidate besides the one matched, you could use "not": | rule "Use WireCandidate" | when | $import : ImportPackage( exporter == null ) | $wc : WireCandidate( importPackage == $import ) | not( WireCandidate( this != $wc, importPackage == $import ) ) | then | System.out.println("Use WireCandidate " + $wc.getImportPackage() + " --> " + $wc.getExportPackage()); | modify ( $wc.getImportPackage() ) { setExporter( $wc.getExportPackage() ) }; | retract ( $wc ); | end | Now, if you want a more general way of counting instances, use the count() function on accumulate: | rule "Use WireCandidate" | when | $import : ImportPackage( exporter == null ) | $wc : WireCandidate( importPackage == $import ) | // checks if the is exactly 1 instance | Number( intValue == 1 ) from accumulate( | $c : WireCandidate( importPackage == $import ), | count($c) ) | then | System.out.println("Use WireCandidate " + $wc.getImportPackage() + " --> " + $wc.getExportPackage()); | modify ( $wc.getImportPackage() ) { setExporter( $wc.getExportPackage() ) }; | retract ( $wc ); | end | View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4264895#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...