Metadata is essentially "data about data". It provides a context for data. It is used to elaborate on existing information and to improve the understanding of its own characteristics and/or use. Industry metadata standards exist in industry verticals such as insurance, banks, manufacturing. In somes contexts, such as database schema, there are hierarchal levels. In data processing, metadata provides information about or documentation of other data managed within an application or environment. Metadata schema usually include a limited number of elements being described, the name of each element and its meaning. Key metadata elements supporting access to published documents include the originator of a work, its title, when and where it was published and the subject areas it covers.
Some of the most popular metadata schemas include:
Dublin CoreAACR2 (Anglo-American Cataloging Rules)
GILS (Government Information Locator Service)
EAD (Encoded Archives Description)
IMS (IMS Global Learning Consortium)
While the syntax is not strictly part of the metadata schema, the data will be unusable, unless the encoding scheme understands the semantics of the metadata schema. The encoding allows the metadata to be processed by a computer program. Important schemes include:
HTML (Hyper-Text Markup Language)
SGML (Standard Generalised Markup Language)
XML (eXtensible Markup Language)
RDF (Resource Description Framework)
MARC (MAchine Readable Cataloging)
MIME (Multipurpose Internet Mail Extensions)
Metadata is about controlling the quality of data entering the data stream. Metadata
enhances retrieval performance. Metadata can improve retrieval, establishing a context for individual descriptors. Appropriate metadata tags around the different data elements allow search engines to seek information in a more discriminating way. The presence of a subject field (metadata element) can be used as a prompt for entering key words, or for use of controlled indexing terms to describe the document. Knowing how metadata works provides information managers with a mechanism for indexing documents more precisely.
Metadata provides a way of managing electronic digital objects. Many software packages use metadata as a way of managing electronic resources, whether it is for records retention schedules or for digital preservation.
Content management systems (CMS), for instance, use metadata to track when a digital object was last updated or verified, who was responsible for its creation and whether any special access conditions apply. Metadata provides a focus for the establishment of standard practices. It is the metadata associated with digital objects that provides a common format for management and manipulation of resources.
Metadata can help to determine the
authenticity of data. Metadata provides an audit trail to establish ownership and authenticity of a digital object such as an electronic document or image. The history of what has happened to a document or record in its life becomes an important part of this. Metadata provides evidence about the provenance of a resource and this underpins good governance, transparency and accountability. This is increasingly important for the many organisations that depend on electronic records rather paper files. It becomes necessary to demonstrate that the electronic document has been kept securely, is a complete record, and has not been tampered with. Metadata provides evidence for the integrity of an electronic document. This is particularly important in a legal context where electronic documents or physical records may be used as evidence in legal proceedings.
Metadata is the key to
interoperability. Interoperability depends on exchange of metadata between systems to establish the nature of the data being transferred and how it should be handled.
E-commerce is one example of interoperating, where several different proprietary systems may need to exchange data. Access to metadata helps to establish the protocols of exchange of data and ways in which it might be exploited.
Metadata is the
future. An increasing number of software and systems suppliers are working to metadata standards or are creating their own standards for metadata. The growth of e-commerce depends on metadata. Many industries are developing their own infrastructure to allow software from different suppliers to work together and exchange data. Metadata generated by content management systems is seeing a renaissance on the internet after its initial use for subject description. Metadata standards are being used by portal software and to provide access to the information content of websites.
Sources:
University of Queensland. "An Introduction to Metadata". UQ Library.
<http://www.library.uq.edu.au/iad/ctmeta4.html>
Accessed April 3, 2009.
Haynes, David. "Five Purposes of Metadata". Cilip.
<http://www.cilip.org.uk/publications/updatemagazine/archive/archive2004/july/update0407.htm>
Accessed April 3, 2009.Data Warehousing Review. "An Introduction to Metadata". Data, Data Everywhere!
<http://www.dwreview.com/Articles/Metadata.html>.
Accessed April 3, 2009.
In accordance with the relational data model, the database is treated as a set of tables. Relationships are represented by values in tables, and data is retrieved by specifying a result table that can be derived from one or more base tables. Here are a few examples of what SQL looks like:
