There is a level of abstraction sitting above all information processing, including that of unstructured data. That level of abstraction is commonly called metadata, which sits above unstructured data just as it sits on top of structured data. It is with metadata that we can see the “larger picture” of what is going on in the systems and components of information processing.
A simplistic definition of metadata is “data about data,” which has been around for as long as there have been information systems. Although the definition gives a flavor of what metadata is, it is not a good definition. A somewhat better description of metadata is that metadata is an abstraction or a classification of data.