Metadata
Metadata is a definition or description of data. On the web, metadata is used to provide information about documents and content items which does not necessarily need to be displayed on the screen. This information can then be used by software such as search engines or management systems. Examples of information commonly stored as metadata include authorship, publication date, modification date, copyright information, and subject keywords.
Dublin Core
The Dublin Core metadata element set is a standard for cross-domain information resource description. Here an information resource is defined to be "anything that has identity". This is the definition used in Internet RFC 2396, "Uniform Resource Identifiers (URI): Generic Syntax", by Tim Berners-Lee et al. There are no fundamental restrictions to the types of resources to which Dublin Core metadata can be assigned.
ISO 19115
A revival in the awareness of the importance of geography and how things relate spatially, combined with the advancement of electronic technology, have caused an expansion in the use of digital geographic information and geographic information systems worldwide. Increasingly, individuals from a wide range of disciplines outside of the geographic sciences and information technologies are capable of producing, enhancing, and modifying digital geographic information. As the number, complexity, and diversity of geographic datasets grow, a method for providing an understanding of all aspects of this data grows in importance. The objective of this International Standard ISO 19115 is to provide a structure for describing digital geographic data. This International Standard is intended to be used by information system analysts, program planners, and developers of geographic information systems, as well as others in order to understand the basic principles and the overall requirements for standardization of geographic information. This International Standard defines metadata elements, provides a schema and establishes a common set of metadata terminology, definitions, and extension procedures.