What Does Semi-Structured Data Mean?
Semi-structured data is data that is neither raw data, nor typed data in a conventional database system. It is structured data, but it is not organized in a rational model, like a table or an object-based graph. A lot of data found on the Web can be described as semi-structured. Data integration especially makes use of semi-structured data.
Techopedia Explains Semi-Structured Data
Some examples of semi-structured data would be BibTex files or a Standard Generalized Markup Language (SGML) document. Files that are semi-structured may contain rational data made up of records, but that data may not be organized in a recognizable structure. Some fields may be missing or contain information that can't be easily described in a database system.
In semi-structured data, the information that is contained within the data is normally associated with a database schema. This is why the information is sometimes called self-describing.