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Format and Resource Types Working Group - Format Element Working Draft, 1998-07-23

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Format Element Working Draft

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Date Issued:
1998-07-23
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Status of Document:
This is a DCMI Working Draft.
Description of Document: The Format (DC.Format) of a resource refers to the medium, data format, and materials of the instantiation of that resource, including its size if required. This is important in resource discovery as it allows a user to discriminate on the basis of the software, hardware, and other infrastructure that might be needed to display, operate or otherwise use the resource. For the sake of interoperability, the value of the data format or media should be selected from an enumerated list, as discussed below.

Format Position Paper (Revised)

The Format (DC.Format) of a resource refers to the medium, data format, and materials of the instantiation of that resource, including its size if required. This is important in resource discovery as it allows a user to discriminate on the basis of the software, hardware, and other infrastructure that might be needed to display, operate or otherwise use the resource. For the sake of interoperability, the value of the data format or media should be selected from an enumerated list, as discussed below.

For electronic resources, it is recommended that a value of DC.Format be selected from the list of Internet Media Types (MIME values) whenever possible. The reference list is maintained at http://www.isi.edu/in-notes/iana/assignments/media-types/media-types. Note that this list is a registry and there is a well-defined procedure for adding new types if appropriate.

The size of a digital resource will normally be given in bytes, but additional measurements may be appropriate for particular resources, for example, duration (in seconds) for a sound, linear or areal dimension (in pixels) for an image, word-count for a text.

For other resources, it is recommended that a value of DC.Format be selected from lists of physical media types, such as provided in the Art and Architecture Thesaurus (AAT), maintained by the Getty Information Institute (in particular, see the Materials facet).

There are many ways of measuring size for physical objects, including linear dimensions, area, volume and mass. The user should be careful to specify these to allow the best performance in resource discovery.


Notes and Future Work

It will clearly be desirable to add additional structure to the specification of Format in order to allow automated processing of the values. This will require that the property "Format" be qualified to indicate which type or aspect of the format is contained in a value, and which vocabulary or encoding scheme is in use. This is particularly important to accommodate the various aspects of "Size".

Structured DC.Format information might also be used to permit the indication of contained formats of nested-format files (for example, a zip-compressed file will have an outermost format "application/zip" but might contain LaTEX source of format "text/vnd.latex-z").

A refined structure for Format will be the subject of discussions concerning Qualified DC.