Consider these six variations of a pattern constraint: $a: Student( $someStudent.name != null ) $b: Student( $someStudent .name != null ) $c: Student( $someStudent. name != null ) $d: Student( $someStudent.getName() != null ) $e: Student( $someStudent .getName() != null ) $f: Student( $someStudent. getName() != null ) Where is the bug - surely a space next to a separator can't do any harm? But indeed - $c is flagged with a not very helpful error message: "Unable to build constraint as ' name' is invalid". Now, what about $d, $e and $f? Is it also $f, b with the space after the dot, which is flagged? Surprise, surprise: here it is $e that's pilloried with a lot of gobbledegook (note the invented "method" $someStudent): Unable to Analyse Expression $someStudent .getName() != null: [Error: unable to resolve method using strict-mode: add2map.Student.$someStudent()] [Near : {... $someStudent .getName() != nul ....}] More fun of this kind is to be had from similar expressions on the RHS, especially when dialect "mvel" is set. Cheers Wolfgang