doesNotUnderstand: aMessage 
	| position |
	position := [:selector | self class properties
				indexOf: selector
				ifAbsent: [^ super doesNotUnderstand: aMessage]].
	aMessage selector last = $:
		ifTrue: [values
				at: (position value: aMessage selector allButLast)
				put: aMessage argument]
		ifFalse: [^ values
				at: (position value: aMessage selector)]