What is metadata?

According to Wikipedia, "meta" is a prefix that comes from the Greek "meta" and means "after, beyond, with" and is equivalent to the concepts of "reflection" or even "depth".

But that doesn't necessarily make things clearer...

To describe the concept of metadata in a few words, we could give the following definition: "A metadatum is a piece of information that describes a resource (a piece of data, a document, etc.) or that gives it context."

Indispensable information

Computer data is, in most cases, unusable if it is stored without any metadata to give it context.

Let's take the example of a simple file stored on a computer's hard drive, simply to be read by the operating system, the latter already needs three indispensable metadata: The file's name/location, its size, and its format (text, document, archive, etc.).

Once opened, it's a text document, where months and sums of money are recorded. Without additional metadata, this file is readable but useless.

It will become interesting once two new pieces of metadata have been discovered:

• Document title: "2021 Salary"
• Author: "John Doe"

As you will have understood, it is thanks not only to the content of the document but also to the metadata that describes it that we were able to have enough information about this file to understand its content.

Note that the examples in this article concern files, but any data can be associated with metadata

A few examples

Generic metadata

Some metadata are found more frequently than others, such as:

• a title,
• the creation date,
• the modification date,
• the author,
• the size,
• the format,
• the language
• etc...

Image/video metadata (exif)

In addition to generic metadata, an image (or sometimes a video) can contain very detailed additional information called EXIF (Exchangeable Image File):

• Device/camera manufacturer
• Orientation (landscape/portrait)
• Geolocation
• Compression
• Exposure time
• Aperture
• etc...

For example, we can use this data to rotate an image according to its original orientation, as in this article!

Audio metadata

Audio contains metadata necessary for playing the data, such as the sampling rate (44KHz for example), as well as the recording precision (512Kb/s for example).

But in the case of music, we can also find information about the work in question such as:

• Album
• Artists
• Year
• Genre
• etc...