In the early days of information technology (1950s – 1970s), computers were mostly mainframes and the information mostly structured data managed by information systems based on hierarchical and then relational databases.

With the emergence of descriptive markup languages such as SGML and XML that add structure other forms of unstructured data or content such as text and streaming data, as well as NoSQL database and knowledge graphs technologies, the distinction between structured and unstructured data or content is less relevant.