Metadata is central to the work of librarians and others who work extensively with digital information. It needs to be understood, as well, by architectural historians who work with digital files of any kind, especially images (see 7 Steps to Understanding XMP Metadata).
Metadata is descriptive information. It is whatever you used to scrawl on a 35mm slide mount to help you remember what it depicts. It is even more important in the digital world because good metadata can not only describe an image effectively, it also allows it to be combined with other digital resources. In the most basic terms, a carefully captioned digital image can be posted on the web and searched via Google or Yahoo!. Structured metadata, using pre-set fields, allows an image to become part of larger, shared collections.
Metadata is only useful if carefully applied. When images are captioned systematically, using, for example, IPTC fields for Location and Photographer, they can be sorted by those fields or placed on a map. Reliable metadata makes efficient retrieval possible. Applied carelessly, or without a widely accepted system, descriptive information does not become part of a larger body of information because it cannot be found. I can write a three-paragraph description on the back of an 8×10 photograph but if I don’t file it carefully, alongside other, similar, images, all the descriptive information in the world won’t help me find it again.
Even when an item is carefully catalogued by an expert, that expert can only contribute information that is at hand. The Library of Congress recognized the limitations even of expert cataloguing when it contributed several thousand of its images to Flickr.com, asking users of the site to add descriptive “tags,” or keywords, to the posted images. Hundreds of people added thousands of tags, identifying in the photographs previously anonymous people, locations and events, and generally applying the collective intelligence of the internet to the cataloguing effort. LC will pull the community-applied information back into their own catalog records to build increasingly descriptive records of those photographs (see George Oates’ summary for a more detailed description and the LC blog for the latest on this project).
Applying good metadata is absolutely necessary for you to find your images again. It also allows you to share those images with others, and to have them help you describe them if you wish. It enables, in any case, sharing of information on a scale unimaginable in the analog world.
All That Is Solid 