Frameworks Frameworks

Standardised Metadata Frameworks

The main problem related to the use of the standardised metadata description schemes is the fixed number of describing attributes and their specialisation on fixed domains with the consequent lesser flexibility in representing needs of particular application domains.
In the light of these difficulties another standard class has been evolved, considering the possibility of integrating more metadata standards mapped on different application domains, providing rich metadata models for media descriptions together with languages allowing the definition of other description schemes for arbitrary domains.
These last standards can be referred as standardised metadata frameworks. They promised simpler interoperability among different application domains and also the possibility to simpler create generic tools able to process multimedia descriptions.
We can summarise the main characteristics of the standardised metadata frameworks in the following points:

No domain-dependence description scheme
Rich generic data-model for multimedia content description
Schema definition languages that allow the definition of description schemes for arbitrary application domains

This section shows some of reference metadata standard frameworks described classifying them according to relevant characteristics [4].
Particular attention has been given to one of the latest initiative following this tendency which is represented by the MPEG-21, a new MPEG metadata standard framework still under development.
The following table shows a resume of the reference metadata standard frameworks.

	PICS	MCF	RDF	XTM
Standardisation body	World Wide Web Consortium (W3C)	World Wide Web Consortium (W3C)	World Wide Web Consortium (W3C)	TopicMaps.org Consortium
Year	1996	1997	1999	2001
Data Model	Attribute based	Semantic network based/directed labelled graphs	Semantic network based/directed labelled graphs	Semantic network based/directed labelled graphs
Schema Definition Language	Rating Systems	Standard vocabulary	RDF Schema	Topic Map Constraint Language (TMCL)
Domain	Qualitative rating og web resources	Machine understandable, semantic description of web resources	Machine understandable, semantic description of web resources	Semantic mapping of information resources
Level	Semantic	Semantic	Semantic	Semantic
MM type	Any	Any	Any	Any

Some characteristics of some reference metadata standard frameworks