Metadata is one of those strange terms to someone has a mysterious fascination unless you are familiar with definition accompanied by what it actually does, it will continue to remain alien to those who encounter this term.
Those of us who have had an opportunity to become familiar with this term, literally, Metadata can be best understood as data being about data described as short, structured and standardised or consistent descriptions of information resources. The idea of Metadata has been around for along time, since the mid-19th century, amongst library cataloguing rules.
Metadata provide short, structured and consistent descriptions of information resources which at best indicate catalogued records. It could be further described as surrogates imitating the actual items used. The main purpose for Metadata is to identify, retrieve, use and manage information resources. It could also be said, digitising information resources into Metadata records makes it easier for retrieval, finding required items by searching or browsing, display, deciding on whether an item is useful; legal status of items; records management or whether it can be shared and exchanged.
Metadata falls into two types: descriptive Metadata and Subject Metadata.
Descriptive Metadata is description of the item itself, it's title, author, date of publication or creation, physical form, etc.
Descriptive Metadata asks lots of questions about the item is:
What is this called?
Who wrote it?
How old is it?
How big is it?
What kind of thing is it
Where is it?
Descriptive Metadata is very detail oriented its not happy just being about content it wants to know what exactly is it unlike subject Metadata who satisfied in telling their story.
Both types of Metadata must conform to the structured and standardised standards.
Subject Metadata describes the content meaning, describes what the item is about.
Subject Metadata uses controlled terms, classification Codes, subject headings, or controlled terminology for example, terms captured from titles and abstracts.
Subject Metadata is very intrusive, it wants to know what item is actually about, the content is plays a major role in telling the story of the item.
Metadata standards importantly govern the content and elements of records in how the same information is presented in the same way.
Machine Readable Cataloguing (MARC) is an exchange format for Metadata records created according to the AACR2 and RDA cataloguing codes.
Dublin Core (DC) is another standard of web Metadata format, which comprises of 15 elements or fields such as, title, creator, subject, and format.
Learning Object Metadata (LOM) this standard holds Metadata for educational resources at all levels of granularity.
Text Encoding Initiative ( TEI) is a standard representation of texts in digital form.
Metadata Encoding and Transmission Standard ( METS )
International Standard for Archival Description (General) (ISAD (G))
Visual Resources Association ( VRA ) Core