Traditional academic libraries usually consist of many shelves of books, filing cabinets of papers and a pile of documents on the desk, chairs and (maybe) floor. I've moved all of that to digital files. By scanning, mostly. Lots of scanning.
The Digital Library Indices
The Digital Library consists mainly of scanned items. The collection is divided into 22 categories. These are personally-meaningful groupings (read: don't nag me about them).
Library items generally occur in a single collection. Sometimes, an item's content will fit with several categories; duplicates are placed in each relevant category.
An overall Author index is provided. It shows the collection in which the document resides.
Each Collection has a date index.