-- operations

evalOperation OPERATION
    ARGUMENT	EvalObject
    RESULT	EvalObject
    ERRORS	{ evalError }
    LINKED	{ read, write }
	::= 0

read OPERATION
    RESULT	EvalObject
    ERRORS	{ endOfInput }
	::= 1

write OPERATION
    ARGUMENT	EvalObject
	::= 2

-- errors

evalError ERROR
    PARAMETER	Service-Diagnostic
	::= 0

endOfInput ERROR
	::= 1

...