It accompanies every file and document that circulates on the web, is present on every website we visit, and in some way can reveal information that is valuable to some and dangerous to others. Metadata is present throughout the digital universe. However, because it is not visible at first glance, even the most geeky citizens are often unaware of its existence. We know it exists and that it is everywhere, but do we really know what metadata is? In this article we are going to make an analysis so that you can finally understand in a simple way what metadata is, what are the types of metadata that exist, and some examples of the most common metadata in our daily life on the Internet.
What is metadata?
If we look for the definition of metadata on the Internet we will find different options, as metadata does not have a single definition. The meaning of metadata is best understood by referring to the etymology of the term metadata itself, which comes from two words in Greek and Latin.
The concept of metadata comes, on the one hand, from the Classical Greek word ‘meta’ (μετα), meaning ‘after, beyond, or about’. This prefix is coupled with the Latin concept ‘datum’, i.e. ‘data’. The most basic meaning of metadata according to its etymology would be ‘about data’. On this basis, the most common and widespread definition of metadata is the following: metadata is data about data.
Definition of metadata according to Jack Myers (creator of the concept)
Although the use of and interest in metadata has grown as the digital revolution has flourished, the concept of metadata existed before the Internet. The term ‘metadata’ was coined in 1969 by Jack E. Myers and trademarked in 1986 by his company, The Metadata Company. The first definition of metadata given (very close to the most widespread definition today) was that of data about data, with the understanding that metadata provides the minimum information necessary to identify a resource.
Technical metadata definition according to NISO
But to understand what metadata is, we may need a more precise definition from a technical point of view. Here we find the National Information Standards Organisation (NISO) definition of metadata, which describes metadata as
“structured information that describes, explains, locates or otherwise facilitates the retrieval, use or management of information”.
From a technical point of view, the best way to know what types of metadata exist is to get lost in the extensive knowledge offered by NISO in this field, specifically in its publication ‘Understanding metadata’, which we recommend reading for a deep understanding of our friends the metadata.
In summary, according to this publication, there are different types of metadata according to their function:
Descriptive metadata
This is the metadata that helps us to find or understand a resource. Some examples of this metadata can be found in any word or pdf document, such as the title of the file, the name of the author of the file or the date of publication of the file.
Administrative metadata
They have a multitude of functions and within these we can find:
Technical metadata, to decode and render the files.
Preservation metadata, for the long-term management of the files.
Rights metadata, for the management of intellectual property rights linked to the content.
Structural metadata
They are the ones that establish relationships of parts of resources to each other, using mark-up languages to embed metadata and other structural features or semantic features within the content.
Our friends metadata have a very wide universe, so the classification of metadata can give rise to infinite types of metadata. To understand this, let’s see what meta tags are.
Examples of metadata
Metadata has that ‘hidden’ feel to it and seems to circulate as a ‘dark mass’ in the Internet universe. However, metadata is actually accessible to anyone who is willing to find it. Here are some examples of metadata that are present in our daily lives on the Internet.
Metadata of a pdf document
PDF documents created with Acrobat 5.0 or any later version contain document metadata in XML (Extensible Markup Language) format. Metadata in pdf documents includes relevant information about the file and the content of the file. Examples of metadata in pdf files may include the name of the author, creation and modification dates of the document, keywords or copyright information.
You can view the metadata of a pdf file in the Document Properties (right click – properties). The metadata of this type of document can also be viewed, expanded or modified using products external to Adobe Acrobat.
Metadata of a photo
The issue of photo metadata is particularly interesting. In the case of photographs, metadata is of great importance because of the privacy risk it poses. Through standards such as EXIF (Exchangeable Image File Format), all photographs taken with a digital device have embedded metadata that can reveal a lot of information, this applies to any image file in .jpg, .tiff, .raw, .png, etc. format. Some examples of photo metadata are:
The name of the owner of the device or camera.
GPS coordinates with the exact location where the photo was taken.
Date and time the photo was taken.
Technical data of the photograph such as the model of camera or device with which the photograph was taken, firmware version used, use of flash, focal length, aperture, ISO level, white balance or the size of the image.
Picture size.
Thumbnail view of the photograph.
Metadata of a video
The metadata of a video is very similar to that of a photograph or image. In addition, they include other metadata related to the video format, some examples of video metadata can be the format in which the video is recorded, video duration, bitrate, which indicates the amount of information (file weight) per time unit, the date of recording and editing, the software used or the codec needed to play it.
