EXIF Alignment
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Alignment of EXIF and M3O
EXIF is a common metadata standard for images and supports mainly technical metadata. It is embedded directly into media assets such as JPEG files. In the following we present the alignment of EXIF and the M3O.
Understanding
The key-value based metadata specified in EXIF is binary encoded into the header of, e.g., JPEG files. Consequently the mapping of the non-semantified concepts onto the scaffold of the M3O posed the major challenge for this particular alignment. Thus, for aligning EXIF and the M3O, we first needed to semantify the key-value pairs of EXIF.
Grouping
The EXIF metadata standard has been translated to a RDF Schema[1] by the W3C through an one-to-one mapping. Here, each key of the EXIF specification has been directly mapped to a corresponding property. This approach ignores the groupings of metadata keys that is provided in the original EXIF specification such as pixel composition and geo location. For the alignment, we have reconstructed this grouping information.
Mapping
Mapping EXIF to the M3O follows a similar procedure as conducted with the mapping of the Ontology of Media Resource. Special consideration is provided on how to map EXIF properties to information objects and information realizations. For example, locations have been constrained to information objects, as they convey information on where the original picture has been taken. Image resolutions describe a quality of a concrete realization, e.g., a JPEG file, and are therefore associated with the information realization instead. Specific properties can be referred to by using preexisting vocabularies, e.g., the WGS84 vocabulary for GPS information. As EXIF restrains itself to describing qualities of multimedia items all keys have been mapped as specialization of the M3O Annotation Pattern.
Consistency Checking and Documentation
We have tested the validity of the resulting ontology using Fact++ and Pellet.
Application of the Aligned Ontology
To represent an EXIF compliant annotation using the M3O, we define an EXIFAnnotationPattern concept The EXIF-AnnotationPattern defines an EXIFGeoParameter that parametrizes a GeoPoint. Within this construct, we accumulate all parameters that can be specified in regards to GPS Attribute Information as specified in EXIF. Going conform with the Data Value Pattern, we express the GeoPoint through geo:lat and geo:long, which specify primitive values of type xsd:decimal. In this case, we want to represent the location at which the image was created and thus attach the information to the information object.
Ontology
exif.owl [1]
