What Does This Text Really Mean?

Imagine that you were tasked with indexing (categorizing and summarizing) the contents of a large collection of randomly formatted text documents to make them easily accessible throughout your company. Perhaps this use case contains legal documents as well as medical records (with various levels of sensitivity). Suppose that the size of this collection contained over 100 million documents that you had to analyze. Besides categorizing each document as medical or legal, you must also assign them to subcategories like cardiology or probate. Finally, you must capture the meaning of each document for reporting and analytics.