Metadata
Metadata or meta-information is actually "information about information. For example, a document's metadata can describe who created it, when it was created and last edited, what language it was written in and what program was used. Metadata can be used, for example, to look up information in a database.
Metadata can be divided into structural metadata, which describes the relationship of the data to other data (often using taxonomy), and descriptive metadata, which is specifically about the information to which it relates.
Where is metadata used?
Some examples of places where metadata is used:
- In a library, to describe the books present and their physical location;
- To provide photo files with information about the camera, including properties such as shutter speed, focus, zoom, time and location.
- Within Web sites, metatags can be added to Web pages that include a short description, keywords, the author, the language and character set used, and any copyright information;
- For video, to provide individual scenes with a description and to possibly send along a transcription of spoken text so that it can be displayed as subtitles;
- A call database records the caller, recipient, start time and duration of each phone call;
- With e-mail, each e-mail message has headers that include the sender, date sent, addressee, subject, spam score and servers that handled the message in transit.
Storage of metadata
Meta information is not part of the information or document to which it relates. Often, however, metadata is stored in the file in question and can be found for programs in the source code. Metadata can also be stored in an external database.
The Telecommunications Data Retention Act requires ISPs and telecom providers to store the meta-information they capture for a certain amount of time for investigative purposes.
