Understanding Metadata What is Metadata? .................................................................................................. 1 What Does Metadata Do? ................................................................................ 1 Structuring Metadata ................................................................................. 2 Metadata Schemes and Element Sets ............................................... 3 Dublin Core .....................................................................................................................3 TEI and METS ..............................................................................................................4 MODS .......................................................................................................................5 EAD and LOM......................................................................................................6 <indecs>, ONIX, CDWA, and VRA ..................................................................7 MPEG ..........................................................................................................8 FGDC and DDI ........................................................................................9 Creating Metadata ................................................ 10 Interoperability and Exchange of Metadata ....11 Future Directions .................................... 12 More Information on Metadata ........ 13 Glossary ...................................... 15 Acknowledgements Understanding Metadata is a revision and expansion of Metadata Made Simpler: A guide for libraries published by NISO Press in 2001. NISO Press extends its thanks and appreciation to Rebecca Guenther and Jacqueline Radebaugh, staff members in the Library of Congress Network Development and MARC Standards Office, for sharing their expertise and contributing to this publication. About NISO NISO, a non-profit association accredited by the American National Standards Institute (ANSI), identifies, develops, maintains, and publishes technical standards to manage information in our changing and ever-more digital environment. NISO standards apply both traditional and new technologies to the full range of information-related needs, including retrieval, re-purposing, storage, metadata, and preservation. NISO Standards, information about NISO’s activities and membership are featured on the NISO website <http://www.niso.org>. This booklet is available for free on the NISO website (www.niso.org) and in hardcopy from NISO Press. Published by: NISO Press National Information Standards Organization 4733 Bethesda Avenue, Suite 300 Bethesda, MD 20814 USA Email: [email protected] Tel: 301-654-2512 Fax: 301-654-1721 URL: www.niso.org Copyright © 2004 National Information Standards Organization ISBN: 1-880124-62-9 Understanding Metadata What Is Metadata? administrative data; two that in the headers of image files. sometimes are listed as separate Storing metadata with the object it Metadata is structured infor- metadata types are: describes ensures the metadata will mation that describes, explains, not be lost, obviates problems of locates, or otherwise makes it − Rights management meta- linking between data and metadata, easier to retrieve, use, or manage data, which deals with and helps ensure that the metadata an information resource. Metadata intellectual property rights, and object will be updated together. is often called data about data or and However, it is impossible to embed information about information. − Preservation metadata, which metadata in some types of objects The term metadata is used contains information needed (for example, artifacts). Also, storing differently in different communities. to archive and preserve a metadata separately can simplify Some use it to refer to machine resource. the management of the metadata understandable information, while itself and facilitate search and others use it only for records that Metadata can describe re- retrieval. Therefore, metadata is describe electronic resources. In sources at any level of aggregation. commonly stored in a database the library environment, metadata It can describe a collection, a single system and linked to the objects is commonly used for any formal resource, or a component part of a described. scheme of resource description, larger resource (for example, a applying to any type of object, digital photograph in an article). Just as What Does or non-digital. Traditional library cataloging is a form of metadata; Metadata Do? MARC 21 and the rule sets used Metadata is key An important reason for creating with it, such as AACR2, are to ensuring that descriptive metadata is to facilitate metadata standards. Other discovery of relevant information. In metadata schemes have been resources will addition to resource discovery, developed to describe various types survive and metadata can help organize of textual and non-textual objects continue to be electronic resources, facilitate including published books, interoperability and legacy resource electronic documents, archival accessible into integration, provide digital finding aids, art objects, educational the future. identification, and support archiving and training materials, and scientific and preservation. datasets. Resource Discovery There are three main types of catalogers make decisions about metadata: whether a catalog record should be Metadata serves the same • created for a whole set of volumes functions in resource discovery as Descriptive metadata describes or for each particular volume in the good cataloging does by: a resource for purposes such as set, so the metadata creator makes • allowing resources to be found discovery and identification. It similar decisions. Metadata can also by relevant criteria; can include elements such as be used for description at any level title, abstract, author, and of the information model laid out in • identifying resources; keywords. the IFLA (International Federation • bringing similar resources of Library Associations and • Structural metadata indicates together; how compound objects are put Institutions) Functional Require- together, for example, how ments for Bibliographic Records: • distinguishing dissimilar re- pages are ordered to form work, expression, manifestation, or sources; and chapters. item. For example, a metadata • record could describe a report, a giving location information. • Administrative metadata pro- particular edition of the report, or a Organizing Electronic vides information to help specific copy of that edition of the manage a resource, such as report. Resources when and how it was created, file Metadata can be embedded in As the number of Web-based type and other technical a digital object or it can be stored resources grows exponentially, information, and who can access separately. Metadata is often aggregate sites or portals are it. There are several subsets of embedded in HTML documents and increasingly useful in organizing Page 1 links to resources based on digital object may also be given The latter group developed a audience or topic. Such lists can be using a file name, URL (Uniform framework outlining types of built as static webpages, with the Resource Locator), or some more presentation metadata. A follow-up names and locations of the persistent identifier such as a PURL group, PREMIS (PREservation resources “hardcoded” in the (Persistent URL) or DOI (Digital Metadata: Implementation Strat- HTML. However, it is more efficient Object Identifier). Persistent egies)—also sponsored by OCLC and increasingly more common to identifiers are preferred because and RLG—is developing a set of build these pages dynamically from object locations often change, core elements and strategies for the metadata stored in databases. making the standard URL (and encoding, storage, and manage- Various software tools can be used therefore the metadata record) ment of preservation metadata to automatically extract and invalid. In addition to the actual within a digital preservation system. reformat the information for Web elements that point to the object, the Many of these initiatives are based applications. metadata can be combined to act on or compatible with the ISO as a set of identifying data, Reference Model for an Open Interoperability differentiating one object from Archival Information System Describing a resource with another for validation purposes. (OAIS). metadata allows it to be understood Archiving and by both humans and machines in Structuring Metadata ways that promote interoperability. Preservation Metadata schemes (also called Interoperability is the ability of Most current metadata efforts schema) are sets of metadata multiple systems with different center around the discovery of elements designed for a specific hardware and software platforms, recently created resources. purpose, such as describing a data structures, and interfaces to However, there is a growing particular type of information exchange data with minimal loss of concern that digital resources will resource. The definition or meaning content and functionality. Using not survive in usable form into the of the elements themselves is defined metadata schemes, shared future. Digital information is fragile; known as the semantics of the transfer protocols, and crosswalks it can be corrupted or altered, scheme. The values given to between schemes, resources intentionally or unintentionally. It metadata elements are the content. across the network can be may become unusable