Metadata standards have been built by experts in different subject areas with different understandings of their domain, information resources, users and use behaviour, and the overall requirements for sesource discovery and description in their specific domains Some of these metadata formats - MARC 21, Dublin Core and so on - are general in nature and can accommodate descriptive information about digital information resources of different types in different disciplines, while others - the (FGDC's) content standard for digital geospatial metadata, the (ISAD) for archival records and so on - are more specialized and apply to information in a specific discipline or domain.