<metadata>

-"data about data".

- 이 용어의 개념이 모호한데 그 이유는 two fundamentally different concepts을 포함하고 있기 때문이다:

= Structural metadata;

the design and specification of data structures에 대한 것이며, 보다 정확하게는 "data about the containers of data"라 부른다.

- Descriptive metadata;

individual instances of application data 즉, the data content에 관한 것이다. 따라서, "data about data content" or "content about content" 그러므로 metacontent라고 부르는 것이 더욱 좋을 것이다.

Metadata (metacontent)는 전통적으로 도서관 목록에서 찾을 수 있다. 정보가 점점 더 디지털화됨으로써, 메타데이터 역시 특별한 학문영역에 전문적으로 적용되는 메타데이터 표준을 사용하여 디지털 데이터를 기술하는데 이용되고 있다. 데이터 파일의 contents와 context를 기술함으로써, 오리지널 데이터/파일의 질이 크게 높아진다. 예를 들어, 이용자의 경험을 자동적으로 개선시킬 수 있도록 하는 브라우저를 통하여어떤 웹페이지에 사용된 언어, 만들 도구, 그 주제에 대해 더 알고 싶은 경우에 가야할 장소를 자세하게 나타내는 메타데이터를 포함할 수도 있다.

1. Definition

Metadata (metacontent)란 데이터와 관련해서 다음과 같은 한 가지 이상의 aspect에 대한 정보를 제공하는 데이터이다;

1)Means of creation of the data

2)Purpose of the data

3)Time and date of creation

4)Creator or author of the data

5)Location on a computer network where the data were created

6)Standards used

예) a digital image에 그 그림이 만들어졌을 때의 그 그림의 크기, 색도, 해상도 등과 같은 metadata가 포함될 수 있다.  텍스트 문서의 메타데이터에는 how long the document is, who the author is, when the document was written, and a short summary of the document 에 대한 정보가 포함될 수 있다..

Metadata는 데이터이다. 따라서 메타데이터는 데이터베이스에 저장되어 관리될 수 있다. 종종 이 데이터베이스를 Metadata registry or Metadata repository라 부른다. 그렇지만,  context and a point of reference가 없다면, 그것은 메타데이터를 단지 살펴보기만 함으로써 메타데이터를 식별해내지 못할 수도 있다. 예를 들어, 모두 13 digits로 이루어진 여러 개의 번호들을 포함하고 있는 데이터베이스는 그 자체가 계산의 결과이거나 방정식에 사용할 숫자의 리스트일 수도 있다 --만일 어떤 다른 context가 없다면, 번호들 그 자체가 데이터로 인식될 수 있다. 그러나 이 데이터베이스가 장서수집용 a log라는 context가 주어진다면, 이러한 13자리 번호들은 ISNSs - 그 책속에 들어 있는 정보 자체가 아니라 그 책에 대하여 말하는 정보- 으로 이제는 식별되어질 수 있다.

The term "metadata" was coined in 1968 by Philip Bagley, in his book "Extension of programming language concepts" where it is clear that he uses the term in the ISO 11179 "traditional" sense, which is "structural metadata" i.e. "data about the containers of data"; rather than the alternate sense "content about individual instances of data content" or metacontent, the type of data usually found in library catalogues. Since then the fields of information management, information science, information technology, librarianship and GIS have widely adopted the term. In these fields the word metadata is defined as "data about data".[6] While this is the generally accepted definition, various disciplines have adopted their own more specific explanation and uses of the term.

2. Metadata types

Bretheron & Singley (1994)의 two distinct classes: structural/control metadata and guide metadata.

1) Structural metadata

tables, columns and indexes와 같은 computer systems의 structure를 기술하기 위하여 사용된다.

2) Guide metadata

사람이 특별한 아이템을 찾는 것을 도와주기 위하여 사용되며, 대부분 자연어로된 키워드의 세트로 표현된다. Ralph Kimball의 메타데이터의 2 similar categories: technical metadata와 business metadata. Technical metadata는 internal metadata이고, business metadata는 external metadata이다. Kimball은 a third category로 process metadata를 추가하였다. 또 한편으로 NISO의 구분 - three types of metadata: descriptive, structural and administrative. Descriptive metadata란  title, author, subjects, keywords, publisher와 같은 객체(object)를 탐색하고 그 위치를 설정하기 위하여 사용되는 정보이고, structural metadata란 how the components of the object are organised에 대한 기술이며, administrative metadata란 file type을 포함하고 있는 the technical information을 말하며, Two sub-types of administrative metadata에는 rights management metadata와 preservation metadata가 있다..

3. Metadata structures

Metadata (metacontent), or more correctly, the vocabularies used to assemble metadata (metacontent) statements, are typically structured according to a standardized concept using a well-defined metadata scheme, 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.

4. Metadata syntax

Metadata (metacontent) syntax refers to the rules created to structure the fields or elements of metadata (metacontent).[10] 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.[11]

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) (i.e. books having the number 514 on their spine) the implied statement is: "<book><subject heading><514>.

This is a subject-predicate-object triple, or more importantly, a class-attribute-value triple. The first two elements of the triple (class, attribute) are pieces of some structural metadata having a defined semantic. The third element is a value, preferably from some controlled vocabulary, some reference (master) data. The combination of the metadata and master data elements results in a statement which is a metacontent statement i.e. "metacontent = metadata + master data". All 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(Unified Modeling Language (UML) is a standardized, general-purpose modeling language in the field of software engineering. The Unified Modeling Language includes a set of graphic notation techniques to create visual models of object-oriented software-intensive systems.),

EDIFACT(United Nations/Electronic Data Interchange For Administration, Commerce and Transport (UN/EDIFACT) is the international EDI standard developed under the United Nations. The work of maintenance and further development of this standard is done through the United Nations Centre for Trade Facilitation and Electronic Business (UN/CEFACT) under the UN Economic Commission for Europe, in the Finance Domain working group UN CEFACT TBG5. EDIFACT has been adopted by the International Organization for Standardization (ISO) as the ISO standard ISO 9735.),

XSD(XML Schema, published as a W3C recommendation in May 2001,[1] is one of several XML schema languages. It was the first separate schema language for XML to achieve Recommendation status by the W3C. Because of confusion between XML Schema as a specific W3C specification, and the use of the same term to describe schema languages in general, some parts of the user community referred to this language as WXS, an initialism for W3C XML Schema, while others referred to it as XSD, an initialism for XML Schema Definition.[2][3] In Version 1.1 the W3C has chosen to adopt XSD as the preferred name, and that is the name used in this article.),

Dewey/UDC/LoC,

SKOS(Simple Knowledge Organization System (SKOS) is a W3C recommendation designed for representation of thesauri, classification schemes, taxonomies, subject-heading systems, or any other type of structured controlled vocabulary. SKOS is part of the Semantic Web family of standards built upon RDF and RDFS, and its main objective is to enable easy publication and use of such vocabularies as linked data.),

ISO-25964(ISO 25964 is the international standard for thesauri, published in two parts as follows: ISO 25964  Information and documentation - Thesauri and interoperability with other vocabularies

Part 1: Thesauri for information retrieval

Part 2: Interoperability with other vocabularies)

Pantone(Pantone Inc. is a corporation headquartered in Carlstadt, New Jersey.[1] The company is best known for its Pantone Matching System (PMS), a proprietary color space used in a variety of industries, primarily printing, though sometimes in the manufacture of colored paint, fabric, and plastics.)

Linnaean Binomial Nomenclature(Binomial nomenclature (also called binominal nomenclature or binary nomenclature) is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens. The formal introduction of this system of naming species is credited to Swedish natural scientist Carl Linnaeus, effectively beginning with his work Species Plantarum in 1753.), etc.

Using controlled vocabularies for the components of metacontent statements, whether for indexing or finding, is endorsed by ISO-25964: "If both the indexer and the searcher are guided to choose the same term for the same concept, then relevant documents will be retrieved." This is particularly relevant when considering that the behemoth of the internet, Google, is simply indexing then matching text strings, there is no intelligence or "inferencing" occurring.

5. Metadata standards

International standards apply to metadata. Much work is being accomplished in the national and international standards communities, especially ANSI (American National Standards Institute) and ISO (International Organization for Standardization) to reach consensus on standardizing metadata and registries.

The core standard is ISO/IEC 11179-1:2004 [14] and subsequent standards (see ISO/IEC 11179). All yet published registrations according to this standard cover just the definition of metadata and do not serve the structuring of metadata storage or retrieval neither any administrative standardisation. It is important to note that this standard refers to metadata as the data about containers of the data and not to metadata (metacontent) as the data about the data contents. It should also be noted that this standard describes itself originally as a "data element" registry, describing disembodied data elements, and explicitly disavows the capability of containing complex structures. Thus the original term "data element" is more applicable than the later applied buzzword "metadata".

The Dublin Core metadata terms are a set of vocabulary terms which can be used to describe resources for the purposes of discovery. The original set of 15 classic [2] metadata terms, known as the Dublin Core Metadata Element Set [3] are endorsed in the following standards documents:

IETF RFC 5013 [4]

ISO Standard 15836-2009 [5]

NISO Standard Z39.85 [6].

Although not a standard, Microformat (also mentionned in the section metadata on the internet below) is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata. Microformat follows XHTML and HTML standards but is not a standard in itself. One advocate of microformats, Tantek Çelik, characterized a problem with alternative approaches:

“ Here's a new language we want you to learn, and now you need to output these additional files on your server. It's a hassle. (Microformats) lower the barrier to entry

6. Library and information science and metadata

Libraries employ metadata in library catalogues, most commonly as part of an Integrated Library Management System. Metadata are obtained by cataloguing resources such as books, periodicals, DVDs, web pages or digital images. These data are stored in the integrated library management system, ILMS, using the MARC metadata standard. The purpose is to direct patrons to the physical or electronic location of items or areas they seek as well as to provide a description of the item/s in question.

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 library principles, the focus on non-librarian use, especially in providing metadata, means they do not follow traditional or common cataloging approaches. Given the custom nature of included materials, metadata fields are often specially created e.g. taxonomic classification fields, location fields, keywords or copyright statement. Standard file information such as file size and format are usually automatically included.[16]

Standardization for library operation has been a key topic in international standardization (ISO) for decades. Standards for metadata in digital libraries include Dublin Core, METS, MODS, DDI, ISO standard Digital Object Identifier (DOI), ISO standard Uniform Resource Name (URN), PREMIS schema, Ecological Metadata Language, and OAI-PMH. Leading libraries in the world give hints on their metadata standards strategies

1)Dublin Core

The Dublin Core metadata terms are a set of vocabulary terms which can be used to describe resources for the purposes of discovery. The terms can be used to describe a full range of web resources (video, images, web pages, etc.), physical resources such as books and objects like artworks.[1] The full set of Dublin Core metadata terms can be found on the Dublin Core Metadata Initiative (DCMI) website.[2] The original set of 15 classic [3] metadata terms, known as the Dublin

Core Metadata Element Set [4] are endorsed in the following standards documents:

IETF RFC 5013 [5]

ISO Standard 15836-2009 [6]

NISO Standard Z39.85 [7]

Dublin Core Metadata can be used for multiple purposes, from simple resource description, to combining metadata vocabularies of different metadata standards, to providing interoperability for metadata vocabularies in the Linked data cloud and Semantic web implementations

2)METS( The Metadata Encoding and Transmission Standard)

a metadata standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, expressed using the XML schema language of the World Wide Web Consortium. The standard is maintained in the Network Development and MARC Standards Office of the Library of Congress, and is being developed as an initiative of the Digital Library Federation.

METS is an XML Schema designed for the purpose of:

(1) Creating XML document instances that express the hierarchical structure of

digital library objects.

(2) Recording the names and locations of the files that comprise those objects.

(3) Recording associated metadata. METS can, therefore, be used as a tool for

modeling real world objects, such as particular document types.

Depending on its use, a METS document could be used in the role of Submission Information Package (SIP), Archival Information Package (AIP), or Dissemination Information Package (DIP) within the Open Archival Information System  Reference Model.

(OAIS: An Open Archival Information System)

- an archive, consisting of an organization of people and systems, that has accepted the responsibility to preserve information and make it available for a Designated Community.

- The information being maintained has been deemed to need "long term preservation", even if the OAIS itself is not permanent. "Long term" is long enough to be concerned with the impacts of changing technologies, including support for new media and data formats, or with a changing user community. "Long term" may extend indefinitely. In this reference model there is a particular focus on digital information, both as the primary forms of information held and as supporting information for both digitally and physically archived materials. Therefore, the model accommodates information that is inherently non-digital (e.g., a physical sample), but the modeling and preservation of such information is not addressed in detail.

The reference model:

(1)provides a framework for the understanding and increased awareness of archival

concepts needed for long term digital information preservation and access.

(2)provides the concepts needed by non-archival organizations to be effective

participants in the preservation process.

(3)provides a framework, including terminology and concepts, for describing and

comparing architectures and operations of existing and future archives.

(4)provides a framework for describing and comparing different long term

preservation strategies and techniques.

(5)provides a basis for comparing the data models of digital information preserved

by Archives and for discussing how data models and the underlying information

may change over time.

(6)provides a foundation that may be expanded by other efforts to cover long-term

preservation of information that is not in digital form (e.g., physical media and

physical samples).

(7)expands consensus on the elements and processes for long-term digital

information preservation and access, and promotes a larger market which

vendors can support.

(8)guides the identification and production of OAIS-related standards.[2]

3)MODS(The Metadata Object Description Schema)

an XML-based bibliographic description schema developed by the United States Library of Congress' Network Development and Standards Office. MODS was designed as a compromise between the complexity of the MARC format used by libraries and the extreme simplicity of Dublin Core metadata.

The MODS record has been designed to carry key data elements from the MARC record but does not define all of the MARC fields and does not use the field and subfield tagging from the MARC standard. There are data elements in MODS that are not compatible with the MARC record so there is some loss translating from MARC to MODS and from MODS to MARC. There is no commitment on the part of the Library of Congress to maintain compatibility between the two metadata formats beyond what is convenient to the community of MODS users.

The use of MODS provides several advantages compared to other metadata schemas:

(1)High compatibility with existing resource descriptions

(2)Less detail than MARC so various internal record element sets can be mapped to

MODS

(3Item descriptions from outside in DC and other simpler formats can be mapped

and enhanced

4)DDI(The Data Documentation Initiative)

an international project to create a standard for information describing statistical and social science data. Begun in 1995, the effort brings together data professionals from around the world to develop the standard. The DDI specification, written in XML, provides a format for content, exchange, and preservation of information. Version 3.1 of the DDI standard was released in 2009.[1]

5)ISO standard Digital Object Identifier (DOI)

A digital object identifier (DOI) is a character string (a "digital identifier") used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata may change. Referring to an online document by its DOI provides more stable linking than simply referring to it by its URL, because if its URL changes, the publisher need only update the metadata for the DOI to link to the new URL.

DOI names

A DOI name takes the form of a character string divided into two parts, a prefix and a suffix, separated by a slash. The prefix identifies the registrant of the name, and the suffix is chosen by the registrant and identifies the specific object associated with that DOI. Most legal Unicode characters are allowed in these strings, which are interpreted in a case-insensitive manner.

For example, in the DOI name 10.1000/182, the prefix is 10.1000 and the suffix is 182. The "10." part of the prefix identifies the DOI registry,[8] and the characters 1000 in the prefix identify the registrant; in this case the registrant is the International DOI Foundation itself. 182 is the suffix, or item ID, identifying a single object (in this case, the latest version of the DOI Handbook). Citations using DOI names should be printed as doi:10.1000/182. When the citation is a hypertext link, it is recommended to embed the link as a URL by concatenating "http://dx.doi.org/" to the DOI name, omitting its "doi:" prefix; e.g., the DOI name doi:10.1000/182 is linked as http://dx.doi.org/10.1000/182. This URL provides the location of an HTTP proxy server which will redirect web accesses to the correct online location of the linked item.[4][9]

DOI names can identify creative works (such as texts, images, audio or video items, and software) in both electronic and physical forms, performances, and abstract works[10] such as licenses, parties to a transaction, etc. The names can refer to objects at varying levels of detail: thus DOI names can identify a journal, an individual issue of a journal, an individual article in the journal, or a single table in that article. The choice of level of detail is left to the assigner, but in the DOI system it must be declared as part of the metadata that is associated to a DOI name, using a data dictionary based on the indecs Content Model.

-Comparison with other identifier schemes

A DOI name differs from commonly used Internet pointers to material, such as the Uniform Resource Locator (URL), in that it identifies an object as a first-class entity,[clarification needed] not simply the place where the object is located. It implements the Uniform Resource Identifier (Uniform Resource Name) concept and adds to it a data model and social infrastructure.[15]

A DOI name also differs from standard identifier registries such as the ISBN, ISRC, etc. The purpose of an identifier registry is to manage a given collection of identifiers, whereas the primary purpose of the DOI system is to make a collection of identifiers actionable and interoperable, where that collection can include identifiers from many other controlled collections.[16]

The DOI system offers persistent, semantically-interoperable resolution to related current data and is best suited to material that will be used in services outside the direct control of the issuing assigner (e.g., public citation or managing content of value). It uses a managed registry (providing social and technical infrastructure). It does not assume any specific business model for the provision of identifiers or services and enables other existing services to link to it in defined ways. Several approaches for making identifiers persistent have been proposed. The comparison of persistent identifier approaches is difficult because they are not all doing the same thing. Imprecisely referring to a set of schemes as "identifiers" doesn't mean that they can be compared easily. Other "identifier systems" may be enabling technologies with low barriers to entry, providing an easy to use labeling mechanism that allows anyone to set up a new instance (examples include Persistent Uniform Resource Locator (PURL), URLs, Globally Unique Identifiers (GUIDs), etc.), but may lack some of the functionality of a registry-controlled scheme and will usually lack accompanying metadata in a controlled scheme. The DOI system does not have this approach and should not be compared directly to such identifier schemes. Various applications using such enabling technologies with added features have been devised that meet some of the features offered by the DOI system for specific sectors (e.g., ARK).

A DOI name does not depend on the object's location and, in this way, is similar to a Uniform Resource Name (URN) or PURL but differs from an ordinary URL. URLs are often used as substitute identifiers for documents on the Internet (better characterised as Uniform Resource Identifiers) although the same document at two different locations has two URLs. By contrast, persistent identifiers such as DOI names identify objects as first class entities: two instances of the same object would have the same DOI name.

- Resolution

DOI name resolution is provided through the Handle System, developed by Corporation for National Research Initiatives, and is freely available to any user encountering a DOI name. Resolution redirects the user from a DOI name to one or more pieces of typed data: URLs representing instances of the object, services such as e-mail, or one or more items of metadata. To the Handle System, a DOI name is a handle, and so has a set of values assigned to it and may be thought of as a record that consists of a group of fields. Each handle value must have a data type specified in its "<type>" field, that defines the syntax and semantics of its data.

To resolve a DOI name, it may be input to a DOI resolver (e.g., at www.doi.org) or may be represented as an HTTP string by preceding the DOI name by the string

http://dx.doi.org/

For example, the DOI name 10.1000/182 can be resolved at the address "http://dx.doi.org/10.1000/182". Web pages or other hypertext documents can include hypertext links in this form. Some browsers allow the direct resolution of a DOI (or other handles) with an add-on, e.g., CNRI Handle Extension for Firefox. The CNRI Handle Extension for Firefox enables the browser to access handle or DOI URIs like hdl:4263537/4000 or doi:10.1000/1 using the native Handle System protocol. It will even replace references to web-to-handle proxy servers with native resolution.

- Organizational structure

The International DOI Foundation (IDF), a non-profit organisation created in 1998, is the governance body of the DOI system.[17] It safeguards all intellectual property rights relating to the DOI system, manages common operational features, and supports the development and promotion of the DOI system. The IDF ensures that any improvements made to the DOI system (including creation, maintenance, registration, resolution and policymaking of DOI names) are available to any DOI registrant. It also prevents third parties from imposing additional licensing requirements beyond those of the IDF on users of the DOI system.

The IDF is controlled by a Board elected by the members of the Foundation, with an appointed Managing Agent who is responsible for co-ordinating and planning its activities. Membership is open to all organizations with an interest in electronic publishing and related enabling technologies. The IDF holds annual open meetings on the topics of DOI and related issues.

Registration agencies, appointed by the IDF, provide services to DOI registrants: they allocate DOI prefixes, register DOI names, and provide the necessary infrastructure to allow registrants to declare and maintain metadata and state data. Registration agencies are also expected to actively promote the widespread adoption of the DOI system, to cooperate with the IDF in the development of the DOI system as a whole, and to provide services on behalf of their specific user community. A list of current RAs is maintained by the International DOI Foundation.

Registration agencies generally charge a fee to assign a new DOI name; parts of these fees are used to support the IDF. The DOI system overall, through the IDF, operates on a not-for-profit cost recovery basis.

- Standardization

The DOI system is an international standard developed by the International Organization for Standardization in its technical committee on identification and description, TC46/SC9.[18] The Draft International Standard ISO/DIS 26324, Information and documentation - Digital Object Identifier System met the ISO requirements for approval. The relevant ISO Working Group later submitted an edited version to ISO for distribution as an FDIS (Final Draft International Standard) ballot,[19] which was approved by 100% of those voting in a ballot closing on November 15, 2010.[20] The final standard was published on April 23, 2012.[21]

DOI is a registered URI under the infoURI[22] specification (IETF RFC 4452), "The "info" URI Scheme for Information Assets with Identifiers in Public Namespaces";[23] info:doi/ is the infoURI Namespace of Digital Object Identifiers.

The DOI syntax is a NISO standard, first standardised in 2000, ANSI/NISO Z39.84-2005 Syntax for the Digital Object Identifier

6)ISO standard Uniform Resource Name (URN)

A uniform resource name (URN) is the historical name for a uniform resource identifier (URI) that uses the urn: scheme.

Defined in 1997 in RFC 2141, URNs were intended to serve as persistent, location-independent identifiers for resources, allowing the simple mapping of namespaces into a single URN namespace.[1] The existence of such a URI does not imply availability of the identified resource, but such URIs are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable.[2]

Since RFC 3986[2] in 2005, the use of the term has been deprecated in favor of the less-restrictive "URI", a view proposed by a joint working group between the W3C and IETF.[3] Both URNs (names) and URLs (locators) are URIs, and a particular URI may be a name and a locator at the same time.

URNs were originally intended in the 1990s to be part of a three-part information architecture for the Internet, along with URLs and URCs, a metadata framework. However, URCs never progressed past the conceptual stage,[3] and other technologies such as the Resource Description Framework later took their place.

**URC-a uniform resource characteristic (URC) is a string of characters representing the metadata of a URI (uniform resource identifier, a string identifying a Web resource). A URC binds a URI's associated URN (uniform resource name, a unique name for a Web resource) to its URL (uniform resource locator, the location at which a Web resource can be found).

7)PREMIS schema(PREservation Metadata: Implementation Strategies)

an international working group concerned with developing metadata for use in digital preservation.

In 2003 the Online Computer Library Center (OCLC) and Research Libraries Group (RLG) established the PREMIS working group, which consisted of a multi-national roster of more than thirty representatives from the cultural, government, and private sectors, in order to define implementable, core preservation metadata, with guidelines/recommendations for management and use.[1] PREMIS was “charged to define a set of semantic units that are implementation independent, practically oriented, and likely to be needed by most preservation repositories”.[2]

In May 2005, PREMIS released Data Dictionary for Preservation Metadata: Final Report of the PREMIS Working Group. This 237-page report includes: PREMIS Data Dictionary 1.0: a comprehensive, practical resource for implementing preservation metadata in digital archiving systems; accompanying report (providing context, data model, assumptions); special topics, glossary, usage examples; set of XML schema which was developed to support use of the Data Dictionary.[3] Version 2.0 of PREMIS was released in March 2008.[4

- Entities

The PREMIS data model consists of five interrelated entities: Intellectual, Object, Event, Agent, and Rights with each semantic unit mapped to one of these areas.[5]

An intellectual entity is a set of content that constitutes a discrete, coherent intellectual unit, such as a book or a database. These may be compound objects containing other intellectual entities and may have multiple digital representations.[6] Descriptive metadata is usually applied at this level; given the proliferation of competing schemes, the working group did not define any further descriptive semantic units[7] and allowed for interoperability through “extension containers” (containers hold a related group of semantic units) that can be used for external schemes.[6]

Most of the semantic units listed in the data dictionary relate to object and event entities, the former being further divided into three subtypes of file, bitstream, and representation. A file is the level at which most end users are used to working, a “named and ordered sequence of bytes that is known by an operating system.” It includes a variety of file system attributes, rendering it understandable by an operating system, encompassing bitstreams, which are “contiguous or non-contiguous data within a file that has meaningful common properties for preservation purposes.” A representation is, in a sense, the “highest level” of this model, for it may encompass several files in order to properly render the structure and content of an intellectual entity. Not all repositories will be concerned with preserving representations,[8] depending on their purpose and the curatorial body’s need to preserve what might be considered the entity’s digital “intrinsic value.” Furthermore, intellectual entities may have multiple representations within a repository. Events interrelate with objects insofar as they involve actions that have an effect on them or agents ("a person, organization, or software...associated with Events...or with Rights attached to an object") associated with the object.[6]

Finally, the inclusion of rights entities responds to an increased awareness of and concern for the legal requirements of copyright and licensing. It also includes information about the specific actions permitted; for example, semantic unit 4.1.6.1, act, “the action the preservation repository is allowed to take,” includes such suggested values as replicate, migrate, and delete.[9]

- Data dictionary

PREMIS data dictionary entries include twelve attribute fields, not all of which are applied to every semantic unit (analogous to an "element" in other metadata schemes). In addition to the name and definition of the unit, the fields record such things as rationale for including the unit, usage notes, and examples of how the value might be filled in. Four of the attributes - object category, applicability, repeatability, and obligation - are linked, as the last three are defined for each of the object entity levels of file, bitstream, and representation. The dictionary is hierarchical; some semantic units are contained within others. For example, 1.3 preservationLevel, includes four semantic components, such as 1.3.1 preservationLevelValue and 1.3.2 preservationLevelRole.[10]

8)Ecological Metadata Language

Ecological Metadata Language (EML) is a metadata standard developed by and for the ecology discipline. It is based on prior work done by the Ecological Society of America and others,[1] including the Knowledge Network for Biocomplexity.[2] EML is a set of XML schema documents that allow for the structural expression of metadata. It was developed specifically to allow researchers to document a typical data set in the ecological sciences.

EML is largely designed to describe digital resources, however, it may also be used to describe non-digital resources such as paper maps and other non-digital media.

9)OAI-PMH(Open Archives Initiative Protocol for Metadata Harvesting)

a protocol developed by the Open Archives Initiative. It is used to harvest (or collect) the metadata descriptions of the records in an archive so that services can be built using metadata from many archives. An implementation of OAI-PMH must support representing metadata in Dublin Core, but may also support additional representations.

The protocol is usually just referred to as the OAI Protocol.

OAI-PMH uses XML over HTTP