Structured Data – data in databases, centrally organized. Can be protected with standard security: host-oriented and application-oriented security.

Unstructured Data – data files that exist throughout an environment. A document management system basically adds structure to it and centralizes it so that you can apply the same controls as above. Unstructured, distributed data requires distributed access control associated with the data = Digital Rights Management.

It is extremely difficult in this day and age to constrain data. Data warehouses are a good example of shared information, even structured data, that loses its location-association very quickly, so applying access control to an application is not a great solution for data.