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3.13 Format
The Format (M60) element is an NAA element intended to describe the physical representation of the record. The physical representation includes the type of the record (e.g. audio), the data format (e.g. WAV), the medium (e.g. CD-R), and the size of the record.
The definition of this element assumes that a record contains one physical object (e.g. a single PDF file which contains a document). In VERS, a Record may consist of multiple Documents, each of which can contain multiple Encodings. Neither a Record nor the Document consequently has a specific format in VERS. When it is necessary to represent format information PROV recommends that this information is held in an Encoding (M126) element.
Figure 12. Subelements of the Format element.
The subelements of Format are:
- Media Format (M61). The broad mode of the record: text, video, audio, image, or compound. If it is necessary to represent the media format in a VERS record, it is recommended that this information be added to the Document Type (M124) element. The Media Format subelement must be present if a Format (M60) element is present.
- Data Format (M62). The file format that represents the contents of the record; for example AVI, Real Audio, PDF. In VERS the file format of each Encoding is represented in the File Encoding (M128), Rendering Text (M131) and Rendering Keywords (M132) elements. These elements should always be used in preference to Data Format (M62). The Data Format subelement must be present if a Format (M60) element is present.
- Medium (M63). The physical object on which the record is recorded; for example, a CD or a tape. A VEO is a computer file; it is intended to be independent of the piece of media on which it resides at any point in time. Many storage systems will automatically relocate stored objects from one piece of media to another to optimise access. For these reasons, it is not recommended that this element be used in VERS. The Medium subelement must be present if a Format (M60) element is present.
- Extent (M64). The physical size of the record. The unit (e.g. gigabyte) is not specified in the NAA Standard and so the value must include it. In VERS the size of the record is the size of the VEO and can be directly determined from the file system. For this reason, it is not recommended that this element be used in VERS.
An example of the XML representation of a Format follows:
<naa:Format>
<naa:MediaFormat>Video</naa:MediaFormat>
<naa:DataFormat>MPEG</naa:DataFormat>
<naa:Medium>DVD</naa:Medium>
<naa:Extent>1.4 GB</naa:Extent>
</naa:Format>
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