Techniques To Assist The Location And Retrieval Of Local Images

Summary

Use of a consistent naming scheme and directory structure, as well as controlled vocabulary or thesaurus improve the likelihood that digitised content captured by many people over an extended period will be organized in a consistent manner that avoid ambiguity and can be quickly located.

This QA paper describes techniques to aid the storage and successful location of digital images.

Storing local images

Effective categorization of images stored on a local drive can be equally as important as storing them in an image management system. Digitisation projects that involve the scanning and manipulating of a large number of images will benefit from a consistent approach to file naming and directory structure.

An effective naming convention should identify the categories that will aid the user when finding a specific file. To achieve this, the digitisers should ask themselves:

• What type of information should be identified?
• What is the most effective method of describing this information in shorthand?

This can be better described with an example. A digitisation project is capturing photographs taken during wartime Britain. They have identified location, year and photographer as search criteria for locating images. To organize this information in a consistent manner the project team should establish a directory structure, common vocabulary and shorthand terms for describing specific locations. Figure 1 outlines a common description framework:

Potential Problems

To avoid problems that may occur when the image collection expands or is transferred to a different system, the naming convention should also take account the possibility that:

• Some or all of this information may not be available (e.g. the year may be unknown)
• Several photographs are likely to exist that possess the same criteria, same location, year and photographer.
• Operating systems (OS) and Content Management Systems (CMS) treat lower case, upper case, and filename spaces in a different manner. To maintain consistency, filenames should be written in lower case and spaces should be avoided or replaced with underscores.
• Older operating systems or filing systems (e.g. ISO 9660) use the 8.3 DOS filename restrictions, which may cause problems when accessing these files.
• Some characters are illegal on different operating systems. Mac OS cannot use a colon in a filename, while DOS/Windows identifies ?[]/\=+<>:;", as illegal.

Naming conventions will allow the project to avoid the majority of these problems. For example, a placeholder may be chosen if one of the identifiers is unknown (e.g. 'ukn' for unknown location, 9999 for year). Special care should be taken to ensure this placeholder is not easily mistaken for a known location or date. Additional criteria, such as other photo attributes or a numbering system, may also be used to distinguish images taken by the same person, in the same year, at the same location.

Identification of Digital Derivatives

Digital derivatives (i.e. images that have been altered in some way and saved under a different name) introduce further complications in how you distinguish the original from the altered version. This will vary according to the type of changes made. On a simple level, you may simply choose a different file extension or store files in two different directories (Original and modified). Alternatively you may append additional criteria onto the filename (e.g. _sm for smaller images or thumbnails, _orig and _modif for original and modified).

Further Information

• FILTER - Focusing Images for Learning and Teaching,
  <http://www.filter.ac.uk/>
• MacWindows Tutorial, John Rizzo, 2001,
  <http://www.macwindows.com/tutfiles.html>
• Controlling your language - links to metadata vocabularies, TASI,
  <http://www.tasi.ac.uk/resources/vocabs.html>
• File Naming, TASI
  <http://www.tasi.ac.uk/advice/creating/filenaming.html>