ISO 639-3:2007, Codes for the representation of names of languages – Part 3: Alpha-3 code for comprehensive coverage of languages, is an international standard for language codes in the ISO 639 series. It defines three-letter codes for identifying languages. The standard was published by International Organization for Standardization (ISO) on 1 February 2007. ISO 639-3 extends the ISO 639-2 alpha-3 codes with an aim to cover all known natural languages. The extended language coverage was based primarily on the language codes used in the Ethnologue (volumes 10–14) published by SIL International, which is now the registration authority for ISO 639-3. It provides an enumeration of languages as complete as possible, including living and extinct, ancient and constructed, major and minor, written and unwritten. However, it does not include reconstructed languages such as Proto-Indo-European. ISO 639-3 is intended for use as metadata codes in a wide range of applications. It is widely used in computer and information systems, such as the Internet, in which many languages need to be supported. In archives and other information storage, it is used in cataloging systems, indicating what language a resource is in or about. The codes are also frequently used in the linguistic literature and elsewhere to compensate for the fact that language names may be obscure or ambiguous. Language codes ISO 639-3 includes all languages in ISO 639-1 and all individual languages in ISO 639-2. ISO 639-1 and ISO 639-2 focused on major languages, most frequently represented in the total body of the world's literature. Since ISO 639-2 also includes language collections and Part 3 does not, ISO 639-3 is not a superset of ISO 639-2. Where B and T codes exist in ISO 639-2, ISO 639-3 uses the T-codes. , the standard contains 7,893 entries. The inventory of languages is based on a number of sources including: the individual languages contained in 639–2, modern languages from the Ethnologue, historic varieties, ancient languages and artificial languages from the Linguist List, as well as languages recommended within the annual public commenting period. Machine-readable data files are provided by the registration authority. Mappings from ISO 639-1 or ISO 639–2 to ISO 639-3 can be done using these data files. ISO 639-3 is intended to assume distinctions based on criteria that are not entirely objective. It is not intended to document or provide identifiers for dialects or other sub-language variations. Nevertheless, judgments regarding distinctions between languages