ED-99/DO-272 states that if "a particular attribute is "null," "unknown," "not entered," or "not applicable", it shall be listed as such". AIXM 5.1.1 makes use of GML's nilReason codelist in order to capture such details.

These values can be mapped as follows:

ED-99/DO-272	AIXM 5.1.1
null	Note: AIXM allows empty attributes
unknown	unknown
not entered	missing OR withheld OR template
not applicable	inapplicable

ED-119/DO-291 goes on to provide the exact encoding of the default values to be used in an AMDB.

Browser not supported