Metadata – a mini-glossary
Find definitions, published standards and some useful resources here.
Labels. Most definitions of metadata start by saying that “‘metadata’ literally means ‘data about data.” In a technical, database-y kind of way, that’s exactly true. But for us it’s labels. We’re talking about behind-the-scenes labels attached to digital content assets. We refer to photographs, mostly, but the assets could be just about anything. We’re most interested in the “labels” that are defined in the IPTC standard. IPTC metadata, or a subset of it, is displayed by all popular desktop operating systems (in file info or properties), most photo editing applications, by purpose specific apps on mobile devices, and is automatically applied in many publishing systems.
IPTC (International Press Telecommunications Council) metadata tells us what is depicted in a photo, who made the photo, to whom it belongs, its copyright status, and other information that might help us understand, publish, archive and manage the asset. The IPTC publishes a standard defining “properties” or fields that contain and organize the information. “IPTC metadata” refers to metadata that conforms to the IPTC standard, regardless of how that metadata is actually embedded in a file.
The IPTC has published a getting-started guide for Google Images’ new support of some rights related metadata. Read it here.
With the latest version of their Photo Metadata Standard, the IPTC has released a very useful Users Guide to photo metadata. See it here.
IIM (Information Interchange Model) is an old IPTC standard for a subset of IPTC fields, written in a certain format in the header of an image file. IIM is not able to accommodate all of the current IPTC fields. IPTC/IIM metadata is still embedded in image files, as legacy applications still make use of it. One day, it will likely disappear. Many people erroneously think that IPTC metadata is IIM metadata. It’s not. IPTC is the standard (or schema, in tech-speak). IIM is/was a platform on which IPTC metadata is/was written. Is that clear? I didn’t think so. Developers might be interested in the IIM schema and specification.
XMP (eXtensible Metadata Platform) metadata is an open standard platform on which most any kind of metadata can be recorded. XMP was developed by Adobe in the early part of this century and subsequently released as an ISO standard in 2008. (It’s in three volumes: Part 1, Part2, Part 3) Modern IPTC metadata is encoded on the XMP platform. So “IPTC metadata” refers to IPTC metadata carried in the XMP space, as well as a second (partial) copy that lives on its own in the old IIM format. Applications can record most anything they like in XMP format. Adobe applications, in particular, make extensive use of XMP to record logging and technical data related to an image.
Exif (Exchangeable Image File Format) is, in addition to being the only acronym I know of that’s not all caps, a metadata standard that defines the schema used to record logging information from digital cameras. Exif data records contain things like the settings used on the camera to make the photo and a thumbnail of the photo. GPS data, if it’s present, is stored in Exif metadata. For the most part, Exif data is not intended to be editable, although it can be read and written by many applications.
Metadata working group
The Metadata Working Group is, in its own words “a consortium of leading companies in the digital media industry, focused on the following goals:
- Preservation and seamless interoperability of digital image metadata
- Interoperability and availability to all applications, devices, and services”
In other words, it’s an industry group that creates a standard that defines how software developers should implement all those other standards.
Online metadata viewer
The IPTC has an excellent online tool for viewing image metadata. Access it here.
Is “metadata” singular or plural?
In common usage, “metadata” is treated as a mass noun, like “luggage”, or “sand”, and is, therefore, singular. “Data” is obviously plural, and “metadata” is a compound word based on “data” so that might not seem right or just to grammarians. But logic and justice don’t always prevail. Think, “Big data is changing the world.” Some suggest that the singular of “metadata” is “metadatum”. Others think that “metadatum” feels a lot like an ironic neologism. Unfortunately, there is no single source of truth for the English language.* So it’s up to me, and, for this site, I’m going with metadata as singular, unless I’m forced into a construction like, “The seven metadata suggest something something.” And I promise to try to avoid that.
* Unless, of course, the deities at the AP Stylebook have ruled on an issue. 🙂 They have not spoken on this matter.