My basic assumption to hold up to light of reason:
1 - there are files.
2 - there are data about those files.
Files can live in a file storage system
Data can live in a database.
at a user level (without getting into the tech of how a relational database is implemented on disk) databases should not be stored in unstable environments, such as distributed, non-local file systems which don’t honour file locking mechanisms (etc) of databases.
Files can be stored in any good-enough file store, given necessary and sufficient backup and security protocols are implemented.
This is so general that it can be true and false at the same time. Files contain data. Files can live in a database. „Data about the files“ can live in the file system (think extended attributes and Spotlight meta data).
The Apple dictionary app has this definition of “data”:
• facts and statistics collected together for reference or analysis …
• the quantities, characters, or symbols on which operations are performed by a computer, which may be stored and transmitted in the form of electrical signals and recorded on magnetic, optical, or mechanical recording media.
• Philosophy: things known or assumed as facts, making the basis of reasoning or calculation.
Data is basically information. It can live in your head, on a piece of paper, or even on a road sign. In social psychology a narrative or a discourse between two people may be data – even their gestures and facial expressions may be usable information for the purposes of certain studies, not to mention their clothes and many other things.
Your division isn’t wrong but perhaps clearer terms would help. I would recommend documents and metadata. So restating and clarifying your thesis…
There are documents. Documents do live in the filesystem. They may live in a Finder folder and indexed into a database or inside the database’s internals for imported documents.
There is metadata about those documents. This would include file attributes, full text of indexable formats, and user-defined metadata, including tags/ratings/etc. Re: DEVONthink, metadata is located inside the database’s internal structure.
We try not to be too pedantic but we do try to encourage consistent terminology for easier communication.
Some helpful resources beyond this forum are the Getting Started chapter and the Appendix > Glossary in the built-in Help and manual. Also the Help > Tutorials > Understand the UI.