Standards Standards

Multimedia Metadata Standards

Metadata is the value-added information which documents the administrative, descriptive, preservation, technical and usage history characteristics associated with resources. It provides the underlying foundation upon which digital resources management systems are based to provide fast, precise access to relevant resources across networks and between organizations.
Multimedia content analysis refers to understand semantic meanings of MM documents by means of metadata extracted using common techniques of image and signal processing and image analysis and understanding.
Metadata is an important aspect of the creation and management of digital images and other MM files. The information contained in metadata standards can regards the following aspects:
Following these standards helps organizations to consistently record information about their MM documents in a way that facilitates retrieval and sharing in a networked environment.
Metadata for MM documents can be classify according to the following three types:
  1. Descriptive or Content metadata: is information about the object captured in the document (the object's name, title, materials, dates, physical description, etc..). Content metadata is very important, as it is the main way by which people can search and retrieve the MM documents from a database. There are standards available to assist in determining what information should be recorded about the object, and how to record it.
  2. Technical metadata: is also essential to properly manage digital images. Technical metadata is data about the MM document itself (not about an object in the document). For example, for a digital image, it can include information about: the technical processes used in image capture or manipulation or colour or file formats, and some of the technical information that is recorded about the image, such as the image file type, must be machine-readable (following specific technical formats) so that, a computer system will be able to properly display the image.
  3. Administrative metadata includes information related to the management of MM documents (such as rights management).
MM Metadata can be also classified according to other criteria considering the level of data description, the producibility and the domain dependence [4].
They can be classified by:
  1. Level: we can distinguish between a technical level in which lower level aspects of the MM content is described and a semantic level in which aspects of higher level of abstraction on the MM content are taken into account.
  2. Producibility: the production of metadata can either be automatic, which is a very desirable property from the economic point of view, and regards more frequently the low level technical metadata; for semantic metadata describing the information covered by MM content it is typically required human knowledge. So in these cases the metadata production is manually performed.
  3. Dependencies: metadata can be domain-dependent, for instance the position of a tumour can be interesting for medical applications, while the colour distribution of an image can be useful for many application domains. Metadata can also be media type-dependent considering for instance the colour distribution as applicable only to visual media while the creation date applicable to any media.
Metadata represents surely a gain in terms of benefits produced for MM data descriptions but most of all for MM applications (content analysis).
There are also disadvantages related to metadata. Some of them are its cost, its unreliability, its subjectivity, its lack of authentication and its lack of interoperability with respect to syntax, semantics, vocabularies and languages. However, there are many researchers currently investigating strategies to overcome different aspects of these limitations in an effort to provide more efficient means of organizing content on the Internet.
The main reference topics related to techniques and projects developed for MM content analysis can be briefly summarised as follows [3]:
A large number of metadata standardisation initiatives has been developed in recent years, in order to describe MM contents in so many different domains and to grant sharing, exchanging and interoperability across wide range networks.
We can distinguish between two different standard typology, according to what each of them represents in terms of its functionalities.
The first typology is directly related to the representation of MM content for a specific domain and each of these standards can be referred as a standardised description scheme, while the second one considers the possibility of integrating more metadata standards mapped on different application domains, providing rich metadata models for media descriptions together with languages allowing one to define other description schemes for arbitrary domains.
The table below represents a selection of several metadata standards description schemes, which can be considered the most frequently cited and representative for a quite wide range of different application domains. So, in the following table is illustrated a list of descriptive characteristics of each reference standard taken in account. In particular, information about standardisation bodies, last version dates, described MM data types, application domains, description semantic levels and the way by which metadata has been produced (manually or automatically) have been considered.

MARC Dublin Core CDWA VRA Core CSDGM Z39.87 LOM DIG35 METS JPX SMPTE Metadata Dictionary
Standardization Body Library of Congress Dublin Core Metadata Initiative (DCMI) Art Information Task Force (AITF) Visual Resource Association Federal Geographi Data Committee (FDDC) National Information Standard Organization (NISO) IEE (LTSC) Digital Imaging Group (DIG of I3A) Digital Library Federation (DLF) Joint Photographic Experts Group (JPEG) Society of Motion Picture and Television Engineers (SMPTE)
Year Current Version MARC 21 since 1999 Current Version 1.1 since 1999 Current Version 2.0 since 2000 Current Version 3.0 since 2002 1998 2002 2002 Current Version 1.1 April 2001 Last Review 2001 2000 Last Review 2004
MM Type Any Any Any Images Any Images Any Images Any Images Any
Domain Bibliographic media description Bibliographic media description Description of Art works Description of images of Art works Description of Geographic media Description of still images Description of educational media Description of digital images Description of digital objects Description of digital images Description of audio/video objects
Level Largely semantic Largely semantic Largely semantic Largely semantic Semantic and technical Technical Largely semantic Semantic and technical Semantic and technical Semantic and technical Semantic and technical
Producibility Mainly manual Mainly manual Mainly manual Mainly manual Manual and Authomatic Mainly automatic Mainly manual Mainly manual Mainly manual Mainly manual Manual and Authomatic

Selection of several standardised description schemes