Description Service uses DROID for format identification and JHOVE for format validation and characterization. Based on the identification result, the Format Description Service launches applicable JHOVE validators to perform format validation and characterization. The JHOVE characterization and validation results are then transformed into PREMIS along with applicable standard metadata schema.
General file metadata such as format information, file size, checksum, creator, create date, inhibitors are extracted and expressed in PREMIS schema. The Description Service currently exports the following standard format-specific metadata schema,
- MIX 2.0 for image metadata in JPEG, JP2 and TIFF
- proposed AES-X098B for audio metadata in WAVE and AIFF. Please see JHOVE website for more details.
- TextMD for describing the metadata in ASCII, UTF8 and XML.
- DocMD for document metadata in PDF.
Description service utilize PREMIS event objects to record validation result. General validation result is recorded the eventDetail, for example, this following line indicates that the file is both well-formed and valid according to the file format specification.
<eventDetail>Well-Formed and valid</eventDetail>
If there is any anomaly detected during format validation, it will be recorded in the eventOutcomeDetailExtension section.
<anomaly>Improperly formed date</anomaly>