Metadata: a New Word for an Old Concept
Department of Library and Information Science
Faculty of Psychology and Education
Allame Taba-tabaee University
Department of Medical Library and Information Sciences
Faculty of Management and Medical Information Science
Iran University of Medical Sciences
Metadata, or "data about data," is a new word based on an old concept. In libraries, cataloging is the process of creating metadata. A card-catalog containing information about a book is a simple example of metadata describing characteristics of an information resource. Regardless of old concepts, the term "metadata" is used particularly in the context of modern information systems and electronic networks.
Metadata has been defined in various ways. Tim Berners Lee defined metadata as "machine-readable information about electronic resources or other things" (1997). This definition addresses metadata applied to electronic resources and refers to "data" in a broader scope that includes not only textual, but non-textual information such as graphics, music, or anything likely to appear in an electronic format. It is clear that metadata can be deployed for non-digital objects too . But as mentioned, it most commonly refers to digital information especially on the Web.
Another definition of metadata is that assigned by the DESIRE project: "Data associated with objects which relieves their potential users of having to have full advance knowledge of their existence and characteristics" (2000). The basic purposes of metadata are covered by this definition, including a wide range of operations such as discovery, description, management, and long-term preservation of information resources. Metadata also facilitates and improves the information retrieval process (when examined with a view towards recall and precision criteria), by identifying the major concepts of the information resource.
Main Types of Metadata
The abovementioned definitions address three main t ypes of metadata. According to the North Carolina ECHO (Exploring Cultural Heritage Online) Guidelines for Digitization (2006), these are:
Other categorizations of metadata exist. One of them is as follow:Administrative, Descriptive, Preservation, Technical, and Use metadata (Gill, Gilliland, & Woodley, 2000).
The essential information that metadata gives about a resource is: how it was gathered, the purpose of its gathering, manifestation and manipulation, intellectual properties, and content descriptions such as title, subject, and abstract. This information is represented by a limited number of elements. Each element can take one or more values. These elements are originally defined by one of the metadata schemas. The elements must be embedded in an encoding structure-such as HTML or XML-in one of two ways: in the object itself or separately.
There are several metadata schemes that were designed to meet the unique needs of specific users, and the number is growing rapidly, but the most popular schema,Dublin Core, has been accepted as a sort of standard.
In March 1995, a group of librarians, archivists, information professionals, and other parties interested in describing Internet resources, attended a workshop of the National Center for Supercomputing Applications (NCSA) at the Online Computer Library Center (OCLC) in Dublin , Ohio . Their original objective was to create a core set of elements that could be used for categorizing Web-based resources. The outcome of this workshop was 13 core elements, later increased to 15: title, subject, description, source, language, relation, coverage, creator, publisher, contributor, rights, date, type, format, and identifier.
These elements are continually extended for simplicity, and the level of details is increasing to meet the needs of specialized groups. All elements are optional and repeatable. The continuing development of the Dublin Core is managed by the Dublin Core Metadata Initiative (DCMI).
Although the Dublin Core elements are limited and simple, they can be mapped in more complex systems such as MARC. Also the elements can be added for site-specific purpose or specialized fields. Thus the major advantages of the Dublin Core are its usability and flexibility. In addition to the 15 elements, Dublin Core also has 3 qualifiers that give additional information for interpretation of elements and enable it to function in an international context:
With these three qualifiers, Dublin Core also meets higher level scientific and subject-specific resource discovery needs. In the last few years, there has been a motion within the Dublin Core community toward use of the Dublin Core Metadata Element Set for more complex and specialized resource description tasks, and toward developing mechanisms for incorporating such complexity within the basic element set. Made possible by using above qualifiers, this has generally been calledqualification of Dublin Core. Dublin Core, in the hands of information professionals, is expected to provide an alternative to more developed description models such as AACR2/MARC cataloging.
Some other Metadata Element Sets
Dublin Core, though popular, is not the only metadata scheme being used. A few of the most common ones include:
The number of metadata projects is growing rapidly. Probably the biggest obstacle in the way of development of metadata is the variety of different metadata projects. Any group may create its own metadata standards to meet its own specific needs, and creators are free to use whatever elements come to mind. Even if common metadata elements are used, the content of the elements will not be compatible. It seems essential to use a global controlled vocabulary system for all metadata element sets. But this raises another question: would the use of controlled vocabularies make searching less efficient? There is some voluntary coordination between projects at the very top level and developers of these projects have been active in developing "crosswalks" between their systems (Milstead and Feldman, 1999). It is this coordination that may be the key to ensuring future compatibility.
Very special thanks toDariush Alimohamadifor his contributions. The authors gratefully thank him for his revisions on this paper.
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