Metadata is ” data [information] that provides information about other data”.  Three distinct types of metadata exist: descriptive metadata , structural metadata , and administrative metadata . 
- Descriptive metadata describes a resource for such as discovery and identification. It can include elements such as title, abstract, author, and keywords.
- Structural metadata is metadata is a compound of the form. It describes the types, versions, relationships and other characteristics of digital materials. 
- Administrative metadata provides information to help manage a resource, such as when and how it was created, file type and other technical information, and who can access it. 
Metadata was traditionally used in the card catalogs of libraries until the 1980s, when libraries converted their catalog data to digital databases. In the 2000s, digital formats are becoming the prevalent way of storing data and information, metadata is also used to describe digital data using standard metadata .
There are different metadata standards for each discipline (eg, museum collections, digital audio files , websites , etc.). Describing the content and context of data or data files Increases icts usefulness. For example, a web pagemay include a metadata specifying what software language the page is written in (eg, HTML), what tools were used to create it, what subjects the page is about, and where to find more information about the subject. This metadata can automatically improve the reader’s experience and make it easier for users to find the web page online.
A main purpose of metadata is to help users find information and discover resources. Metadata also helps to organize electronic resources, provide digital identification, and support the archiving and preservation of resources. Metadata assists users in resource discovery by identifying resources, bringing similar resources together, distinguishing dissimilar resources, and giving rental information. ”  Metadata of telecommunication activities including Internet traffic is very widely collected by various national governmental organizations. This data is used for the purposes of traffic analysis and can be used for mass surveillance . 
In many countries, the metadata relating to emails, telephone calls, web pages, video traffic, IP connections and cell phone rentals are routinely stored by government organizations. 
Metadata means “data about data”. Although the “meta” prefix (from the Greek preposition and prefix μετά-) means “after” or “beyond”, it is used to mean “about” in epistemology . Metadata is defined as the data providing information about one or more aspects of the data; It is used to summarize basic information about data that can be tracked and working with specific data.  Some examples include:
- Means of creation of the data
- Purpose of the data
- Time and date of creation
- Creator or author of the data
- Location on a computer network where the data was created
- Standards used
- File size
For example, a digital image may be used to describe the width of the image, the color depth, the image resolution, the image, the shutter speed, and other data.  A text document’s metadata may contain information about how long the document is, when the document is written, and a short summary of the document. Metadata within web pages can also contain descriptions of page content, as well as keywords linked to the content.  These links are often referred to as “metatags”, which were used as a primary factor in determining a web site until the late 1990s.  The reliance of metatags in web searches was decreased in the late 1990s because of “keyword stuffing”. Metatags were widely misused to trick search engines into thinking some websites had more relevance in the search than they really did. 
Metadata can be stored and managed in a database , often called a metadata registry or metadata repository .  However, without context and a point of reference, it might be impossible to identify metadata just by looking at it.  For example: by itself, a database containing several numbers, all 13 digits long could be the results of calculations or a list of numbers to plug into an equation . If the goal Given this context That database is a log book of a collection Those 13-digit numbers May be now APPROBATION have ISBNs – Information That Refers to the book, the goal is not Itself information dans le book. The term ”
While the metadata application is manifold, covering a wide variety of fields, there are specialized and well-accepted models to specify types of metadata. Bretherton & Singley (1994) distinguish between two distinct classes: structural / control metadata and guide metadata.  Structural metadata describes the structure of database objects such as tables, columns, keys and indexes. Guide metadata helps humans find specific items and are usually expressed as a set of keywords in a natural language. According to Ralph Kimball metadata can be divided into 2 similar categories: technical metadata and business metadata. Technical metadata corresponds to internal metadata, And business metadata corresponds to external metadata. Kimball adds a third category, process metadata . On the other hand, NISO distinguishes between three types of metadata: descriptive, structural, and administrative. 
Descriptive metadata is typically used for discovery and identification, as information to search and locate an object, such as title, author, subjects, keywords, publisher. Structural metadata describes how the components of an object are organized. An example of structural metadata would be the chapters of a book. Finally, administrative metadata gives information to help manage the source. Administrative metadata refers to the technical information, including file type, or when and how the file was created. Two sub-types of administrative metadata are rights management metadata and preservation metadata. Rights management metadata explains intellectual property rights, While preservation metadata contains information to preserve and save a resource.  [ page needed ]
Metadata (metacontent) or, more correctly, the vocabularies used to assemble metadata (metacontent) statements, is typically structured according to a standardized concept, including: metadata standards and metadata models. Tools such as controlled vocabularies , taxonomies , thesauri , data dictionaries , and metadata registries can be used to apply further standardization to the metadata. Structural metadata commonality is also of paramount importance in data model development and in database design .
Metadata (metacontent) syntax refers to the rules created by the metacontent.  A single metadata scheme may be expressed in a number of different markup or programming languages, each of which requires a different syntax. For example, Dublin Core may be expressed in plain text, HTML , XML , and RDF . 
A common example of (guide) metacontent is the bibliographic classification, the subject, the Dewey Decimal class number . There is always an implied statement in any “classification” of some object. To classify an object as, for example, Dewey class number 514 (Topology). This is a subject-predicate -object triple, or more importantly, a triple class-attribute-value The first two elements of the triple (class, attribute) are pieces of some structural metadata having a defined semantic. Vocabulary, some reference (master) data. The combination of the metadata and the master data elements in a statement is metacontent statement ie “metacontent = metadata + master data”. All of these elements can be thought of as “vocabulary”. Both metadata and master data are vocabularies which can be assembled into metacontent statements. There are many sources of these vocabularies, both meta and master data: UML, EDIFACT, XSD, Dewey / UDC / LoC, SKOS, ISO-25964, Pantone, Linnaean Binomial Nomenclature, etc. The following is a list of documents that may be of interest to the public : “If both the indexer and the searcher are guided to choose the same term for the same concept, then the documents will be retrieved.”  This is particularly relevant when considering search engines of the internet, such as Google. The process indexes then matches text strings using its complex algorithm; There is no intelligence or “inferencing” occurring, just the illusion thereof.
Hierarchical, linear and planar schemata
Metadata schemata can be hierarchical in nature where relationships exist between metadata elements and elements are nested so that parent-child relationships exist between the elements. An example of a hierarchical metadata schema is the IEEE LOM schema, in which metadata elements may belong to a parent metadata element. Metadata schemata can also be one-dimensional, or linear, where each element is completely discrete from other elements and classified according to one dimension only. An example of a linear metadata schema is the Dublin Core schema, which is one dimensional. Metadata schemata are often two dimensional, or planar, where each element is completely discrete from other elements according to two orthogonal dimensions. 
In all cases where the metadata schemata exceeds the planar depiction, some type of hypermapping is required to enable display and view of metadata. Hypermapping practices. 
The degree to which the data or metadata is structured is referred to as “granularity” . “Granularity” refers to how much detail is provided. Metadata with a high granularity for deeper, more detailed, and more structured information. A lower level of granularity means that metadata can be created for considerably lower costs. The major impact of granularity is not only on creation and capture, but moreover on maintenance costs. As soon as the metadata structures become outdated, so too is the access to the referred data. Hence granularity must take into account the effort to create the metadata as well as the effort to maintain it.
International standards apply to metadata. Much work is being accomplished in the national and international standards community, especially ANSI (American National Standards Institute) and ISO (International Organization for Standardization) to reach consensus on standardizing metadata and registries. The core metadata registry standard is ISO / IEC 11179 Metadata Registries (MDR), the framework for the standard is described in ISO / IEC 11179-1: 2004.  A new edition of Part 1 is in its final stage for publication in 2015 or early 2016.  which extends the MDR to support registration of Concept Systems. (See ISO / IEC 11179 ). This standard specifies a schema for the unambiguous use of humans and computers. ISO / IEC 11179 standard refers to metadata as information about data, or “data about data”. In ISO / IEC 11179 Part-3, the information objects are data about Data Elements, Value Domains, and other reusable semantic and representational information objects that describe the meaning and technical details of a data item. This standard also prescribes the details for a metadata registry, and for registering and administering the information objects within a Metadata Registry. ISO / IEC 11179 Part 3, also for the purpose of calculations, Collections of one or more data elements, or other forms of derived data. While this standard describes itself as a “data element” registry, its purpose is to support describing and registering metadata content independently of any particular application, lending the descriptions to be discovered and reused by humans or computers in new applications, databases, gold For analysis of the registered metadata content. This standard shall have the general authority for other kinds of metadata registries, reusing and extending the registration and administration of the standard. Its purpose is to support describing and registering metadata content independently of any particular application, lending the descriptions to be discovered and reused by humans or computers in developing new applications, databases, or for analysis of the registered metadata content. This standard shall have the general authority for other kinds of metadata registries, reusing and extending the registration and administration of the standard. Its purpose is to support describing and registering metadata content independently of any particular application, lending the descriptions to be discovered and reused by humans or computers in developing new applications, databases, or for analysis of the registered metadata content. This standard shall have the general authority for other kinds of metadata registries, reusing and extending the registration and administration of the standard.
The Geospatial community has a tradition of specialized geospatial metadata standards, particularly building on traditions of map and image libraries and catalogs. Formal metadata is usually essential for geospatial data, as common text-processing approaches are not applicable.
The Dublin Core metadata terms are a set of vocabulary terms that can be used to describe resources for the purposes of discovery. The original set of 15 classic  metadata terms, known as the Dublin Core Metadata Element Set  are endorsed in the following standards documents:
- IETF RFC 5013 
- ISO Standard 15836-2009 
- NISO Standard Z39.85. 
ALTHOUGH not a standard Microformat (also MENTIONED in the section metadata on the Internet below) is a web-based approach to semantic markup qui seeks to re-Use Existing HTML / XHTML tags to Convey metadata. Microformat follows XHTML and HTML standards is not a standard in itself. One advocate of microformats, Tantek Çelik , a problem with alternative approaches:
Metadata May be written into a digital picture file That will Identify Who owns it, copyright and contact information, what brand or model of camera created the file, along with exposure information (shutter speed, f-stop, etc.) and descriptive information, Such as keywords about the photo, making the file or image searchable on a computer and / or the Internet. Some metadata is created by the photographer and / or software after downloading to a computer. Most digital cameras write metadata about model number, shutter speed, etc., and some enable you to edit it;  Nikon DSLRs since the Nikon D3 , on most new Canon cameras since the Canon EOS 7D , And on most Pentax DSLRs since the Pentax K-3. Metadata can be used to make organizing in post-production easier with the use of key-wording. Filters can be used to analyze a specific set of photographs and create selections.
Photographic Metadata Standards are governed by organizations that develop the following standards. They include, but are not limited to:
- IPTC Information Interchange Model IIM (International Press Telecommunications Council),
- IPTC Core Schema for XMP
- XMP – Extensible Metadata Platform (an ISO standard)
- Exif – Exchangeable image file format, Maintained by CIPA (Camera & Imaging Products Association) and published by JEITA (Japan Electronics and Information Technology Industries Association)
- Dublin Core (Dublin Core Metadata Initiative – DCMI)
- PLUS (Picture Licensing Universal System).
- VRA Core (Visual Resource Association) 
Information on the times, origins and destinations of phone calls, electronic messages, instant messages and other modes of telecommunication, as opposed to message content, is another form of metadata. Bulk collection of this call detail record by Edward Snowden Intelligence agencies such as the NSA to keep you posted on the Internet. To the agency.
Metadata is a useful tool for describing and describing the descriptors of a computer system. There are two sources in which video metadata is derived: (1) operational gathered metadata, which is information about the content produced, such as the type of equipment, software, date, and location; (2) human-authored metadata, to improve search engine visibility, discoverability, audience engagement, and providing advertising opportunities to video publishers.  In today’s society most professional video editing software has access to metadata. Avid’s MetaSync and Adobe’s Bridge are two prime examples of this. 
Web pages often include metadata in the form of meta tags . Description and keywords in meta tags are commonly used to describe the Web page’s content. Meta elements, including description page, key words, authors of the document, and the document was last modified.  Web page metadata helps search engines and users to find the types of web pages they are looking for.
Metadata can be created either by automated information processing or by manual work. Elementary metadata captured by computers can be used to create a data file. In this context an object refers to any of the following:
- A physical item such as a book, CD, DVD, a paper map, chair, table, flower pot, etc.
- An electronic file such as digital photo, electronic document, program file, database table, etc.
Data virtualization has emerged in the 2000s as the new software technology to complete the virtualization “stack” in the enterprise. Metadata is used in data virtualization servers. Metadata in these servers is saved as persistent repository and describes business objects in various enterprise systems and applications. Structural metadata commonality is also important to support data virtualization.
Statistics and census services
Standardization work has had a broad impact on efforts to build metadata systems in the statistical community [ citation needed ] . Several metadata standards [ which? ] Are described, and their importance to statistical agencies is discussed. Applications of the standards [ which? ] At the Census Bureau, Environmental Protection Agency, Bureau of Labor Statistics, Statistics Canada, and many others are described [ citation needed ] . Emphasis is on the impact of a statistical agency.
Library and information science
Metadata has been used in various ways as a means of cataloging items in libraries in both digital and analog format. Such data helps classify, aggregate, identify, and locate a particular book, DVD, magazine or any object. Until the 1980s, many library catalogs used alpha-numeric string ( call number ), which indicates the physical location of the book within the library’s shelves. The Dewey Decimal System used by the libraries for the classification of library materials by subject is an early example of metadata usage. Beginning in the 1980s and 1990s, many libraries, these paper files with computer databases. These computer databases make it much easier and faster for users to do keyword searches. Another form of older metadata collection is used by US Census Bureau of what is known as the “Long Form.” The Long Form asks questions that are used to create demographic data to find patterns of distribution.  Libraries employ metadata in library catalogs , most commonly as part of an Integrated Library Management System . Metadata is obtained by cataloging resources such as books, periodicals, DVDs, web pages or digital images. This data is stored in the integrated library management system, ILMS , using the standard MARC metadata.
More recent and specialized instances of library metadata include the establishment of digital libraries including e-print repositories and digital image libraries. While often based on non-librarian use, especially in providing metadata, they do not follow traditional or common cataloging approaches. Given the customary nature of included materials, metadata fields are often specially created eg taxonomic classification fields, location fields, keywords or copyright statement. Standard file information  Library operations has been a key topic in efforts towards international standardization . Standards for metadata in digital libraries include Dublin Core , METS , MODS , DDI , DOI , URN , PREMIS schema, EML , and OAI-PMH . Leading libraries in the world give hints on their metadata standards strategies.  
Metadata in a museum context is the Information That trained cultural documentation specialists, Such As archivists , librarians , museum registrars and curators , create to index, structure, describe, identify, gold Otherwise Specify works of art, architecture, cultural objects and Their images.   [ page needed ]  [ page needed ] Descriptive metadata is most commonly used in museum contexts for object identification and resource recovery purposes. 
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Metadata is developed and applied in collecting institutions and museums in order to:
- Facilitate resource discovery and execute search queries. 
- Create digital archives that store information relating to various aspects of museum collections and cultural objects, and archival and managerial purposes. 
- Provide public audiences access to cultural objects through publishing digital content online.  
Many museums and cultural heritage centers, which recognize the diversity of artworks and cultural objects, no single model or standard suffices to describe and catalog cultural works.    For example, a sculpted Indigenous artifact could be classified as an artwork, an archaeological artifact, or an Indigenous heritage item. The early courses of standardization in archiving, description and cataloging dans le museum community Began in the late 1990s with the development of Such standards as Categories for the Description of Works of Art (CDWA) , Spectrum, the Conceptual Reference Model (CIDOC) , Cataloging Cultural Objects (CCO) and the CDWA Lite XML schema .  These standards use HTML and XML markup languages for machine processing, publication and implementation.  The Anglo-American Cataloging Rules (AACR) , originally developed for characterizing books, have also been applied to cultural objects, works of art and architecture.  Standards, such as the CCO, are within a museum’s Collection Management System (CMS) , a database through which museums are able to manage their collections, acquisitions, loans and conservation.  Scholars and Professionals in the Field of Standards and Technologies Create challenges for cultural documentarians, specifically non-technically trained professionals.  [ page needed ] Most collecting institutions and museums use a relational database to categorize cultural works and their images.  Relational databases and metadata to the complex relationships amongst cultural objects and multi-faceted works of art, as well as between objects and places, people and artistic movements.   Relational database structures are also beneficial within collecting institutions and museums because they allow for a clear distinction between cultural objects and their images; An unclear distinction could lead to confusing and inaccurate searches. 
Cultural objects and art works
An object’s materiality, function and purpose, as well as the size, weight and storage requirements of the museum and collection, influence the descriptive depth of The data attributed to the object by cultural documentarians. The established institutional cataloging practices, objectives and assessments of cultural documentarians and database structures are as follows: cultural objects are categorized.   Additionally, museums often employ standardized commercial collection management software that prescribes and limits the ways in which archivists can describe artworks and cultural objects.  As well, Vocabularies to describe cultural objects and artworks in their collections.   Getty Vocabularies and the Library of Congress Controlled Vocabularies are reputable within the museum community and are recommended by CCO standards.  Museums are encouraged to use controlled vocabularies that are contextual and relevant to their collections and enhance the functionality of their digital information systems.   Controlled Vocabularies are beneficial within databases because they provide a high level of consistency, improving resource retrieval.   Metadata structures, Including controlled vocabularies, reflect the ontologies of the systems from which they were created. Often the processes by which cultural objects are described and categorized through the metadata in museums do not reflect the perspectives of the maker communities.  
Museums and the Internet
Metadata has been instrumental in the creation of digital information systems and archives within museums and has made it easier for museums to publish digital content online. This has enabled audiences who could not have access to cultural objects due to geographic or economic barriers to have access to them.  In the 2000s, as more museums have adopted archival standards and created intricate databases, discussions about Linked Databetween museum databases have come up in the museum, archival and library science communities.  Collection Management Systems (CMS) and Digital Asset Management tools can be local or shared systems.  Digital Humanities scholars note many benefits of interoperability between museum databases and collections, while also acknowledging the difficulties achieving such interoperability. 
United States of America
Problems involving metadata in litigation in the United States are becoming widespread. [ When? ] Courts have looked at various questions involving metadata, including the discoverability of metadata by parts. Although the Federal Rules of Civil Procedure have only specified rules concerning electronic documents, the case law has been elaborated on the requirement of parts to reveal metadata.  In October 2009, the Arizona Supreme Court has ruled that metadata records are public record .  Document metadata have proven to be important in legal environments in which litigation has requested metadata, Which may include sensitive information to a certain party in short. Using metadata removal tools to “clean” or redact documents can mitigate the risks of unwittingly sending sensitive data. This process Partially (see data remanence ) Protects from law firms Potentially Damaging leaking of sensitive data through electronic discovery .
In Australia the need to strengthen national security has resulted in the introduction of a new metadata storage law.  This new law means that both security and policing agencies will be allowed to access to two years of an individual’s metadata, supposedly to make it easier to stop any terrorist attacks and serious crimes from happening.
Australian medical research pioneered the definition of metadata for applications in health care. (WHO) umbrella. This article is based on the World Health Organization (WHO) umbrella. The medical community did not accept the standards. 
Data warehouse (DW) is a repository of an electronically stored data. Data warehouses are designed to manage and store the data. Differ data warehouses from business intelligence (BI) systems, Because BI systems are designed to use data to create postponements and analyze the information to Provide strategic guidance to management.  Metadata is an important tool in how data is stored in data warehouses. The purpose of a data warehouse is to house standardized, structured, consistent, integrated, correct, “cleaned” and timely data, extracted from various operational systems in an organization. The extracted data are integrated in the data warehouse environment to provide an enterprise-wide perspective. Data are structured in a way to serve the reporting and analytic requirements. The design of structural metadata commonality using a data modeling method Such As entity relationship model diagramming is significant in Any data warehouse development effort. They detail metadata on each piece of data in the data warehouse. An essential component of a data warehouse / business intelligencesystem is the metadata and tools to manage and retrieve the metadata. Ralph Kimball  [ page needed ] describes metadata as the DNA of the data warehouse as metadata defines the elements of the data warehouse and how they work together. The design of structural metadata commonality using a data modeling method Such As entity relationship model diagramming is significant in Any data warehouse development effort. They detail metadata on each piece of data in the data warehouse. An essential component of a data warehouse / business intelligence system is the metadata and tools to manage and retrieve the metadata. Ralph Kimball  [ page needed ] describes metadata as the DNA of the data warehouse as metadata defines the elements of the data warehouse and how they work together. The design of structural metadata commonality using a data modeling method Such As entity relationship model diagramming is significant in Any data warehouse development effort. They detail metadata on each piece of data in the data warehouse. An essential component of a data warehouse / business intelligence system is the metadata and tools to manage and retrieve the metadata. Ralph Kimball  [ page needed ] describes metadata as the DNA of the data warehouse as metadata defines the elements of the data warehouse and how they work together. An essential component of a data warehouse / business intelligence system is the metadata and tools to manage and retrieve the metadata. Ralph Kimball  [ page needed ] describes metadata as the DNA of the data warehouse as metadata defines the elements of the data warehouse and how they work together. An essential component of a data warehouse / business intelligence system is the metadata and tools to manage and retrieve the metadata. Ralph Kimball  [ page needed ] describes metadata as the DNA of the data warehouse as metadata defines the elements of the data warehouse and how they work together.
Kimball et al.  refers to three main categories of metadata: Technical metadata, business metadata and process metadata. Technical metadata is Primarily definitional , while business process metadata is metadata and descriptive Primarily. The categories sometimes overlap.
- Technical metadata defines the objects and processes in a DW / BI system, as seen from a technical point of view. The technical metadata includes the system metadata, which defines the data structures, dimensions, measurements, and data mining models. Technical metadata defines the data model and the way it is displayed for the users, with the reports, schedules, distribution lists, and user security rights.
- Business metadata is more than just a business. The business metadata tells you what, where they come from, what they mean and what their relationship is to other data in the data warehouse. Business metadata may also serve as a documentation for the DW / BI system. Users who browse the data warehouse are viewing the business metadata.
- Process metadata is used to describe the results of various operations in the data warehouse. Within the ETL process, all key data from tasks is logged on execution. This includes start time, end time, CPU seconds used, disk reads, disk writes, and rows processed. When troubleshooting the ETL or query process, this sort of data is valuable. The DW / BI system is a DW / BI system. Some organizations make a living out of collecting and selling this sort of data to companies – in which case the process metadata becomes the business metadata for the fact and dimension tables. Collecting process metadata in the interest of business people who can use the data to identify the users of their products,
On the Internet
The HTML formats used to define Web Allows for the pages inclusion of a variety of kinds of metadata, from basic descriptive text, dates and keywords to further Top advanced metadata schemes Such as the Dublin Core , e-GMS, and AGLS  standards. Pages can also be geotagged with coordinates . Metadata may be included in the page’s header or in a separate file. Microformats allow metadata to be added to on-page data in a way That regular web users do not see, purpose computers, web crawlers and search engines can Readily access. Many search engines are cautious about using metadata in their ranking algorithms due to the use of search engine optimization, SEO , to improve rankings. See Meta article for further discussion. This cautious attitude may be justified as people, according to Doctorow,  are not executing care and diligence when creating their own metadata and that metadata is used to promote the metadata creators own purposes.  and  and , and  show that the search engines respond to web pages with metadata implementations,  and Google has an announcement on its website showing the meta tags that its search engine understands.
In broadcast industry
In broadcast industry, metadata is linked to audio and video broadcast media to:
- Identify the media: clip or playlist names, duration, timecode , etc.
- describe the content: Notes Regarding the quality of video content, rating, description (for example, During a sports event, keywords like goal , red card will be associated to Some clips)
- Classify media: metadata allows to sort out the media or to easily and quickly find a video content (a TV news could urgently need some archive content for a subject). For example, the BBC has a broad subject classification system, Lonclass , a universal decimal classification .
This metadata can be linked to the video servers . Most major broadcast sport events like FIFA World Cup or Olympic Games use this metadata to distribute their video content to TV stations via keywords . It is often the host broadcaster  which is in charge of organizing metadata through its International Broadcast Center and its video servers. This metadata is recorded by the metadata operators ( loggers ) which associate in live metadata available in metadata grids through software (such as Multicam (LSM) or IPDirector used during the FIFA World Cup or Olympic Games).  
( Metadata ), which is a computational geometry of the metadata . This class of metadata is described more fully on the geospatial metadata article.
Ecological and environmental
Ecological and environmental metadata is intended to document the “who, when, where, why, and how” of data collection for a particular study. This type of data was collected and used for the data collection. Metadata should be generated in a format commonly used by the most relevant science community, such as Darwin Core , Ecological Metadata Language ,  or Dublin Core . Metadata editing tools exist to facilitate metadata generation (eg Metavist,  Mercury: Metadata Search System , Morpho  ).
When first released in 1982, Compact Discs only contained a Table Of Contents (TOC) with the number of tracks on the disc and their length in samples.  [ dead link ]  Fourteen years later in 1996, a revision of the CD Red Book standard added CD-Text to carry additional metadata.  Goal CD-Text was not widely adopted. Shortly thereafter, it has become common for personal computers to retrieve metadata from external sources (eg CDDB, Gracenote ) based on the TOC.
Digital audio formats such as digital audio files superseded music files such as cassette tapes and CDs in the 2000s. Digital audio files could be labelled with more information than could be contained in just the file name. That descriptive information is called the audio tag or audio metadata in general. Computer programs specializing in adding or modifying this information are called tag editors . Metadata can be used to name, describe, catalog and indicate ownership or copyright for a digital audio file, and its presence makes it much easier to locate a specific audio file within a group, typically through use of a search engine that accesses the metadata.
As a result, almost all digital audio formats, including mp3 , broadcast wav and AIFF files, have similar standardized locations that can be populated with metadata. The metadata for compressed and uncompressed digital music is often encoded in the ID3 tag. Common editors such as TagLib support MP3, Ogg Vorbis, FLAC, MPC, Speex, WavPack TrueAudio, WAV, AIFF, MP4, and ASF file formats.
With the availability of Cloud applications, which include metadata to content, metadata is increasingly available over the Internet.
Administration and management
Metadata Can Be Stored Either internally ,  in the Sami have the file structure or data (est aussi cette called Expired embedded metadata ), gold Externally , in a separate file from the gold field Described data. A data repository stores the metadata Typically detached from the data, purpose can be designed to Support Embedded metadata approaches. Each option has advantages and disadvantages:
- Internal storage means metadata always travels as part of the data they describe; Therefore, metadata is always available with the data, and can be manipulated locally. This method creates redundancy (precluding normalization), and does not allow managing all of a system’s metadata in one place. It arguably increases consistency, since the metadata is readily changed whenever the data is changed.
- External storage allows collocating metadata for all the contents, for example in a database, for more efficient searching and management. Redundancy can be avoided by normalizing the metadata’s organization. In this approach, metadata can be used in Streaming media ; Or can be referenced (for example, as a web link) from the transferred content. On the down side, the division of the metadata from the data content, especially in standalone files that refer to their source metadata elsewhere, increases the opportunities for misalignments between the two.
Metadata can be stored in either human-readable or binary form. Storing metadata in a human-readable format such as XML can be useful because users can understand and edit it without specialized tools.  However, text-based formats are rarely optimized for storage capacity, communication time, or processing speed. A binary metadata format allows all human beings to read and write.
Each relational database system has its own mechanisms for storing metadata. Examples of relational-database metadata include:
- Tables of all tables in a database, their names, sizes, and number of rows in each table.
- Tables of columns in each database, what tables they are used in, and the type of data stored in each column.
In database terminology, this set of metadata is referred to as the catalog . The SQL standard specifies a uniform means to access the catalog, called the information schema , but not all databases implement it, even if they implement other aspects of the standard SQL. For an example of database-specific metadata access methods, see Oracle metadata . Programmatic access to metadata is possible using APIs such as JDBC , or SchemaCrawler. 
- Agris: International Information System for the Agricultural Sciences and Technology
- Classification scheme
- Crosswalk (metadata)
- Data Dictionary (aka metadata repository)
- Dublin Core
- GEOMS – Generic Earth Observation Metadata Standard
- Geospatial metadata
- ISO / IEC 11179
- Knowledge tag
- Mercury: Metadata Search System
- Meta element
- Metadata Access Point Interface
- Metadata discovery
- Metadata facility for Java
- Metadata from Wikiversity
- Metadata publishing
- Metadata registry
- METAFOR Common Metadata for Climate Modeling Digital Repositories
- Multicam (LSM)
- Observations and Measurements
- Ontology (computer science)
- Official statistics
- Preservation Metadata
- Semantic Web
- The Metadata Company
- Universal Data Element Framework
- Vocabulary OneSource
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