Use Case: Digital imaging lifecycle
A digital image is the result of a chain of distinct intellectual or artistic creation stages. A digital image may be directly obtained from digital camera. A digital image may be obtained from another image in an analog medium, such as photographs, photographic film, or printed paper, by a scanner or similar device. The original image from which the digital image is derived can represent real world scenes, but it can also represent paintings, drawings, charts, maps, microfilmed books, etc. A digital image can be obtained also by complex processing of non-image data, such as those acquired with tomographic equipment. Finally, a digital image can also be generated from scratch, it can be obtained from a graphics editing program such as Adobe Illustrator, it can be generated by a non-interactive computer program, or it can even be written by hand with a hexadecimal text editor (or even an ASCII editor considering that ASCII Art is a form of digital imaging).
In order to capture the digital imaging domain in its full complexity, some metadata models (e.g. EXIF , PhotoRDF  or DIG35 ) allow a certain separation of the different creation stages and the involved elements, which implies representing not only metadata about the features of the final digital image, but also metadata about the related images from which is derived, i.e. “creation workflow metadata” or “processing history metadata”.
The digital imaging lifecycle can (uses to) be very complex, as shown by the following example:
- “An artistic painter finishes his last creation which is a self portrait painted with oil. His wife, a professional photographer, takes a photo of the painting with her new digital camera. Finally, their son performs some improvements with a known graphics editing program”.
The example shows a digital still image resulted from a chain of three distinct creation stages. Independently of the involved digital rights management issues, the specific metadata of the distinct creation stages could be preserved for search&retrieval tasks. E.g. “I’m looking for big JPEG images of paintings authored by Picasso and obtained from photos by David Meyer not digitally altered”.
The digital imaging lifecycle could be even more complex, as shown in the following example:
- “Hyperrealism is a genre of painting resembling a high resolution photograph. In 1968, Robert Bechtle painted ‘61 Pontiac’, an oil painting obtained from a photograph of a car. In order to publish an image of this painting on the Web, a photographer takes a photo of the painting in the San Francisco Museum of Modern Art. Later, the photograph is digitized and edited”
Here the digital image is the product of four different artistic endeavors, the initial photo, the painting, the photo of the painting and the editing of the digitized version of the photo.
A last simple exercise: "Try to find in your favourite images search engine (e.g. Google Imanges) the image of a tattoo inspired in a famous painting (without using the name of a specific painting)."
Digital imaging lifecycle in current metadata standards
There’re different levels of coverage of the digital imaging lifecycle in the existing metadata standards:
- EXIF  is focused in photographs, and mixes “conventional” metadata of the digital image (e.g. Compression field) with metadata related to the photographic process (e.g. Exposure Time, Manufacturer, Flash) at the same level.
- PhotoRDF  separates metadata into three different RDF schemas: the Dublin Core schema, the Technical schema and the Content schema. The Technical schema offers information about the digital imaging lifecycle such as the type of camera, the type of film, the date the film was developed and the scanner and software used for digitizing.
- DIG35  has an extensive support of metadata fields that are relevant to the creation of the digital image data, i.e. “camera and scanner device information and its capture condition as well as the software or firmware to create such image. It defines the “how” metadata that specifies the pedigree of the image”.