The code for the type of relationship of the item identified by _item_related.name and the defined item. ALTERNATE indicates that the item identified in _item_related.related_name is an alternative expression in terms of its application and attributes to the item in this definition. ALTERNATE_EXCLUSIVE indicates that the item identified in _item_related.related_name is an alternative expression in terms of its application and attributes to the item in this definition. Only one of the alternative forms may be specified. CONVENTION indicates that the item identified in _item_related.related_name differs from the defined item only in terms of a convention in its expression. CONVERSION_CONSTANT indicates that the item identified in _item_related.related_name differs from the defined item only by a known constant. CONVERSION_ARBITRARY indicates that the item identified in _item_related.related_name differs from the defined item only by a arbitrary constant. REPLACES indicates that the defined item replaces the item identified in _item_related.related_name. REPLACEDBY indicates that the defined item is replaced by the item identified in _item_related.related_name. ASSOCIATED_VALUE indicates that the item identified in _item_related.related_name is meaningful when associated with the defined item. ASSOCIATED_ESD indicates that the item identified in _item_related.related_name is the estimated standard deviation of of the defined item.