Metadata Models - International Developments and Implementation

Definitions of metadata often describe them as “data about other data”, sometimes refined through the expression “structured data about data”. This definition over-simplifies the facts, that metadata on one hand have been in use long before the digital age, be it in library catalogues or on inventory cards of museums, and that on the other hand the entity they represent does not necessarily need to be in form of bits and bytes. A highly generic definition for metadata therefore could be “(structured) information about (digital) objects”. Transferred to the digital world “structured information” stands for “structured data”. The term metadata does not solely refer to the representation of existing parts of reality such as data streams or objects, but is applicable as well to describe descriptions – metadata collections like subject gateways or digital libraries can be described in a metadata set as well. The unambiguous use of the term metadata therefore requires to regard the context as well as the levels of complexity to be described and the receivers of the information supplied through metadata. Metadata usually carry structured information like “Author”, “Title”, “Subject” etc, bits of information, that are semantically interconnected. Instead of a fixed term or a standardised format metadata therefore should be understood as a form of language to exchange information on objects like books or digital resources as well as for purposes like archiving. Tom Baker describes Dublin Core, one of the most common metadata formats, as “pidgin for Digital Tourists”. Baker stresses the point that the structure of metadata forms a grammar, whose “basic pattern is easily grasped” and which “is wellsuited to serve as an auxiliary language for digital libraries” (ibid.). Metadata thus offer an elementary level of understanding, either between machines, human beings or in between the two of them.