Common Metadata Standards

This guide describes several standards that offer a good starting point for those seeking a generic metadataData about data. Metadata provides a context for research findings, ideally in a machine-readable format. It enables discovery of data via an electronic interface, and correct use and attribution of findings. Related Guide approach to their data: ISOInternational Standards Organization 19115 and ISO 19139, CSDGMContent Standard for Digital Geospatial Metadata , DIFDirectory Interchange Format, Dublin Core, and ADNADEPT/DLESE/NASA metadata framework. This is not an exhaustive list, but it presents a selection of standards that have the following characteristics:

• Widely-used: adopted by major national or international organizations or communities of practice
• Broadly-applicable: designed to describe a variety of different types of data that marine users might have
• Maintained: actively supported by a standards body and extended and updated as appropriate
• Applicable to content: content standardsA list or hierarchy of required metadata elements to be included in the metadata description. Related Guide that describe the information that must or can be ascribed to a data set. (This is in contrast to format standardsA description of the digital storage and structural requirements of metadata which assures that different software programs are able to read or query the data. Related Guide and transport protocolsA strategy for transmitting data between systems. A protocol can be used not only over the internet, between computers, but also between applications running anywhere. Examples: FTP, SNMP, SSH. .)

ISO 19115 and 19139

Developed by the International Organization for Standardization, ISO 19115 is designed to describe geographic information and services, including extent, quality, spatial and temporal schemaIn the context of metadata, a description of the data represented within a database., spatial reference, distribution, and identification information. It contains both mandatory and optional components that are organized into sections, and it has defined methods for extending the standard to fit specialized needs. The full description of ISO 19115, like all ISO standards, may be purchased from the ISO website. See MMIMarine Metadata Interoperability 's ISO 19115 page for more information. It is a content standard only; a related standard, ISO 19139, defines a format standard called Geographical Metadata XMLeXtensible Markup Language for holding ISO 19115-compliant content. ISO 19115 and 19139 are widely used.

North American Profile of ISO 19115

This standard was developed to replace the CSDGM standard (see below) as the US federal metadata standard for geospatial data. As a profile based on ISO 19115, it is applicable to any kind of geospatial data. Metadata that are compliant with NAP are fully ISO 19115 compliant as well. For links to further information, including the current status of NAP with respect to federal approval, see the MMI reference for NAP.

CSDGM (Content Standard for Digital Geospatial Metadata)

The Content Standard for Digital Geospatial Metadata, often informally called the FGDCFederal Geographic Data Committee Metadata Standard, was developed and is maintained by the Federal Geographic Data Committee, a US governmental organization. It is the official US Federal metadata standard and is mandatory for geospatial data produced by US Federal agencies (though the North American Profile of ISO 19115, presented above, is under consideration as a replacement standard). It has also been adopted by many US state and local governments. Like ISO 19115 and 19139, it is applicable to any geospatial data. See MMI's CSDGM page for more information.

DIF (Directory Interchange Format)

One of the oldest standards, DIF began its development in an Earth Science and Applications Data Systems Workshop held in 1987 as a means of creating catalog interoperabilityThe ability of two or more information systems to exchange metadata with minimal loss of information. Related Guide. The International Directory Network, the body behind the CEOS IDN Master Directory, now maintains DIF and uses it as the metadata standard for its directory. DIF is one of the smaller standards (with respect to the number of elements), having 8 mandatory elements and 36 total elements. The mandatory elements are EntryID, Entry Title, Keywords, ISO Topic Category, Data Center, Summary, Metadata Name, and Metadata Version. The Keywords element is supported by a hierarchical, controlled vocabulary for categorizing earth and atmospheric sciences resources. DIF is designed to work with several other standards. It is compatible with both ISO 19115 and FGDC's CSDGM. See MMI's DIF page for more information.

Dublin Core

Another of the smaller standards, the Dublin Core was originally developed as a way to describe bibliographic data, but now is used more widely, as it provides substantial content flexibility. It has two forms: the simple Dublin Core and the qualified Dublin Core. The former was developed first and consists of 15 standard elements: Contributor, Coverage, Creator, Date, Description, Format, Identifier, Language, Publisher, Relation, Rights, Source, Subject, Title, and Type. All of the elements are optional, and there are no restrictions on how the elements are filled in.

The qualified Dublin Core has three additional elements: Audience, ProvenanceThe record of how a particular metadata value or record came to be. Provenance can include things like when the record was created, accessed or modified., and RightsHolder, as well as a group of qualifiers that either define the meaning of elements more narrowly and specifically or provide encoding schemes. Encoding schemes have further constraints, such as:

• Requiring that entries for an element be taken from a particular controlled vocabulary; for example, requiring that subject terms be taken from the Library of Congress Subject HeadingsA type of multi-level controlled vocabulary in which metadata values are classified into categories which may be broad classes. Related Guide, or another of the approved subject lists.
• Specifying a format; for example, requiring that dates be entered as yyyy-mm-dd.

ISO 15836 is the ISO implementation of the Dublin Core standard. While Dublin Core is a content standard only, the Dublin Core Metadata Initiative, which maintains the standard, also provides encoding guidelines for RDFResource Description Framework , XML, and HTMLHyperText Markup Language format standards in support of their content standard. See MMI's Dublin Core page for more information.

ADN

ADN is the ADEPT/DLESEDigital Library for Earth System Education /NASA metadata framework. It was originally developed to describe educational resources, such as lesson plans and classroom activities, for discoveryUse of metadata values or vocabularies to find metadata or data sets. Related Guide by earth sciences educators. It is now being applied to a much wider variety of data, and emphasizes geospatial and temporal aspects of data. It includes a small set of required elements that the metadata cataloguer must include, such as title, subject, and resource type; another small set for the resource creator to provide, such as language and terms of use; plus a larger set of optional elements that can further describe the content. Many of the elements have controlled vocabulariesA managed list of terms. In the context of vocabularies, management typically includes careful selection of terms, maintenance of terms over time (i.e. addition, deprecation, modification), and presentation of the vocabulary in an accessible format. Related Guide. See MMI's ADN page for more information.