Semi-structured data uses some formal constructs to indicate semantic elements
Semi-structured data doesn’t conform to a formal data model, but uses formal constructs to indicate separate semantic elements within the data. This often looks like adding markup elements such as XML tags to otherwise unstructured data, to make those elements more easily processable computationally.
This approach can be used to avoid ambiguities, for example by adding an ISO format date markup to a date written in text. Although not as simple to process as structured data, semi-structured data can be used to add information to unstructured data that allows for effective processing in many applications.