The concept of Unique Identification (UID) has been around for some time, adopted decades ago by the aerospace and automotive industries to allow for interchange of parts between manufacturers and countries. Forms of UID exist in normal life, from the VIN on your car to the UPC on a can of soup. The UPC is simple in concept. Take an item number assigned by a manufacturer, add a manufacturer ID in front of it and one has a unique identifier that allows item number “00001” to at the same time represent a can of soup, a pack of gum and a box of pencils, depending on the manufacturers ID.
To make UIDs useful, a machine-readable interface, such as a bar code, is specified based on the amount of data in the UID and the environment it is to be read in. UPCs use a compressed linear barcode so they can fit on small packages and be read quickly and reliably in the retail environment. UIDs are much longer than UPCs, so the two-dimensional Data Matrix symbol is used instead.
The US Department of Defense (DOD) began to mandate the use of UIDs around 2004. As the initiative evolved the term Item Unique Identification (IUID) term replaced UID as a more precise way to refer to the DoD’s initiative and to differentiate it from other forms of unique identification. The UID acronym is still in wide use in reference to the DoD requirement, the Registry in which this data is stored and the identifier itself, which is more precisely called a Unique Identifier (UII) and/or Item Unique Identifier (IUID). Use of the more generic term UID remains popular, even if not entirely precise.
Read more about DoD Item Unique Identification (IUID) and Unique Item Identifiers (UII).