Identifier

Identifier

An Identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique class of objects, where the "object" or class may be an idea, physical [countable] object (or class thereof), or physical [noncountable] substance (or class thereof). The abbreviation ID often refers to identity, identification (the process of identifying), or an identifier (that is, an instance of identification). An identifier may be a word, number, letter, symbol, or any combination of those.

The words, numbers, letters, or symbols may follow an encoding system (wherein letters, digits, words, or symbols stand for (represent) ideas or longer names) or they may simply be arbitrary. When an identifier follows an encoding system, it is often referred to as a code or ID code. For instance the ISO/IEC 11179 metadata registry standard defines a code as system of valid symbols that substitute for longer values in contrast to identifiers without symbolic meaning. Identifiers that do not follow any encoding scheme are often said to be arbitrary IDs; they are arbitrarily assigned and have no greater meaning. (cf. nominal number)

Such identifiers are typically used either for human logic-oriented reasons, or for automated computational reasons. Identifiers of entities are very common in real life and in mathematics. They are also used in symbolic logic to symbolize and simplify the representation of complex logical and mathematical expressions. Human brains use and automatically create identifiers all the time. For example, humans name: people, places, things (such as: products, substances, species, classes of objects and substances), ideas, feelings, time periods, events, groups, organizations, belief systems, etc.

Types of identifiers

Arbitrary identifiers

Arbitrary identifiers or arbitrary IDs are identifiers that do not convey any information about the object they identify. They are assigned arbitrarily and are not descriptive. Examples of arbitrary identifiers include the unique serial numbers assigned to cars at the time of manufacture, or the number assigned to a particular bottle of milk on a dairy farm.

Semantic identifiers

Semantic identifiers or semantic IDs are identifiers that convey some information about the object they identify. They are descriptive and are often used in natural language processing. Examples of semantic identifiers include the name of a person, or the title of a book.

Persistent identifiers

Persistent identifiers or persistent IDs are identifiers that are assigned to an object and remain with the object over the course of its life. They are often used in digital libraries and other digital resources. Examples of persistent identifiers include the digital object identifier (DOI) used in academic publishing, or the uniform resource name (URN) used in Internet resources.

See also

• Name
• Label
• Tag
• Metadata
• Unique identifier
• Object identifier
• Digital object identifier
• Uniform resource name

Identifier Resources
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