Editing Identifier (section)

==Metadata==
In metadata, an identifier is a language-independent label, sign or token that uniquely identifies an object within an [[identification scheme]]. The suffix "identifier" is also used as a [[representation term]] when naming a [[data element]].

ID codes may inherently carry [[metadata]] along with them. For example, when you know that the food package in front of you has the identifier "2011-09-25T15:42Z-MFR5-P02-243-45", you not only have that data, you also have the metadata that tells you that it was packaged on September 25, 2011, at 3:42pm UTC, manufactured by Licensed Vendor Number 5, at the Peoria, IL, USA plant, in Building 2, and was the 243rd package off the line in that shift, and was inspected by Inspector Number 45.

Arbitrary identifiers might lack metadata. For example, if a food package just says 100054678214, its ID may not tell anything except identity—no date, manufacturer name, production sequence rank, or inspector number. In some cases, arbitrary identifiers such as sequential serial numbers leak information (i.e. the [[German tank problem]]). Opaque identifiers—identifiers designed to avoid leaking even that small amount of information—include "really [[opaque pointer]]s" and [[universally unique identifier#Version 4 (random)|Version 4 UUIDs]].