MOFM2T11 — Ambiguity detected in Invocation rule Message

The Mof2Text concrete syntax contain the following rules (see p. 22): <OclExpressionCS> ::= ( <PropertyCallExpCS> | <VariableExpCS> | <LiteralExpCS> | <LetExpCS> | <OclMessageExpCS> | <ifExp> | <invocation> ) <invocation> ::= ( <PathNameCS> '(' <actualarglist> ')' | 'super' ) [ <before> ] [ <separator> ] [ <after> ] <actualarglist> ::= ( <OclExpressionCS> ( ',' <OclExpressionCS> )* )? <before> ::= 'before' '(' <OclExpressionCS> ')' <separator> ::= 'separator' '(' <OclExpressionCS> ')' <after> ::= 'after' '(' <OclExpressionCS> ')' The OCL concrete syntax contain the following rules (see OCL Specificacion. Pages 64, 72, 80 and 81) OclExpressionCS ::= PropertyCallExpCS | VariableExpCS | LiteralExpCS | LetExpCS | OclMessageExpCS | IfExpCS PropertyCallExpCS ::= ModelPropertyCallExpCS | LoopExpCS ModelPropertyCallExpCS ::= OperationCallExpCS | AttributeCallExpCS | NavigationCallExpCS OperationCallExpCS ::= OclExpressionCS[1] simpleNameCS OclExpressionCS[2] | OclExpressionCS '->' simpleNameCS '(' argumentsCS? ')' | OclExpressionCS '.' simpleNameCS '(' argumentsCS? ')' | simpleNameCS '(' argumentsCS? ')' | OclExpressionCS '.' simpleNameCS isMarkedPreCS '(' argumentsCS? ')' | simpleNameCS isMarkedPreCS '(' argumentsCS? ')' | pathNameCS '(' argumentsCS? ')' | simpleNameCS OclExpressionCS argumentsCS[1] ::= OclExpressionCS ( ‘,’ argumentsCS[2] )? The conflict appears when the before, separator and after rules are all empty at the same time in the <invocation> MOF2Text rule. In that case the resolution proceeds as follows: OclExpressionCS ::= invocation ::= PathNameCS '(' actualarglist ')' OclExpressionCS ::= PropertyCallExpCS ::= ModelPropertyCallExpCS ::= OperationCallCS ::= pathNameCS '(' argumentsCS? ')' Solution: The best solution I have found to avoid this conflict involves the introduction of a new keyword, 'invoke'. The invocation rule could be updated as follows: <invocation> ::= invoke ( <PathNameCS> '(' <actualarglist> ')' | 'super' ) [ <before> ] [ <separator> ] [ <after> ] This way we can distinguish easily between the two cases. TemplateInvocation, MacroInvocation and QueryInvocation would then always resolve unambiguously into this last rule.