"When the extent of holdings is explicitly recorded, this standard requires the recording of those pieces held rather than of those pieces not held." (ANSI/NISO Z39.71-1999, p. 2, 1.2.4. Pieces Held) See also p. 26: "Record and display data in a positive sense; that is, emphasize that which is held rather than that which is not." Gaps shall be indicated and are determined by the absence of any bibliographic unit at any level of order designators (first order or any subsequent order.).
EXCEPTION. RECON ONLY. For subsequent orders of designation, incomplete volumes detailing issues missing or issues held are recorded separately. (See example at 14. below.)
Extent of holdings must be based on examination of the physical items. If the physical items cannot be examined, the Recon technique must be used.