Conferred property values can be changed or "erased" when, after the topic map graph has been altered, conferred property values are recalculated, and a node's situation no longer requires one of its properties to have the value that had been conferred upon it on account of its previous situation (see parid0429 6.3). By contrast, as specified in parid0245 4.7.1 (above), built-in values cannot be changed or erased.

should be treated under definition of conferred values, perhaps
even so far as to state that since the value is conferred by a
situation, then if the situation changes, the value may, or may not change