-The order that attributes are placed into the attribute buffer
-almost invariably matches the order of the attribute mask bit values.
-The exception is
-.Dv ATTR_CMN_FLAGS .
-If its order was based on its bit position, it would be before
-the
-.Dv ATTR_CMN_NAMEDATTRCOUNT
-/
-.Dv ATTR_CMN_NAMEDATTRLIST
-pair, however,
-it is placed in the buffer after them.
+A generation count value of 0 is invalid and cannot be used to
+determine data change.
+.Pp
+The generation count is invalid while a file is mmap'ed. An invalid
+generation count value of 0 will be returned for mmap'ed files.
+.
+.It ATTR_CMN_DOCUMENT_ID
+A
+.Vt u_int32_t
+containing the document id. The document id is a value assigned
+by the kernel to a document (which can be a file or directory)
+and is used to track the data regardless of where it gets moved.
+The document id survives safe saves; i.e it is sticky to the path it
+was assigned to. Requesting this attribute requires the
+FSOPT_ATTR_CMN_EXTENDED option flag.
+.Pp
+A document id of 0 is invalid.