I'm not from the department, I know, I know...
I recently have looked a bit on this:
http://nwn.bioware.com/developers/General remarks:
This is industry-standard thingy. Successfull. With a 6 or 7 digit budget. We cannot mimick it, but we can learn from them. This knowledge is for free. Documents are short, most often this are tables you can only draw conclusion from, don't even have to read it all, just have a glance (unless you're into, lets say generic attributes and character design). This are great docs and they describe creating content for a great engine throughly. There are some specific things to the genre - 3D things, what is creature leaving after death, would it be respawned, also map is presented as a set of waypoints, so in ordinary way for 3D games to implement A* thingy easily.
Just a quick summary:
The engines utilizes files for its purpose and its "how to store data" to be described. Files are in format brewed for the purpose of reading data from them extremely fast. I don't know if there is a database-like backend for that (looks so), or are they opened in other way.
Remarkable things @ GFF file format:
File format is uniform.
File has an index at the beginning with info where each entry is stored within it
Entries have different, fixed types (like integers, bytes, strings)
Many files may be compressed into one, and its engine to handle it later.
Things I have noticed with file structure:
Assets, like inventory item "icon" bitmap file, can be found easily, they have name generated in very rigid and disciplined way. Also all the things seem to reside in a single directory.
There is still some redundancy - unused or obsolete fields are in specs.
Data is really atomized into host of smaller files. But a single files stores only information for a single purpose (like journal entries).
Data is really carefully planed. Makes big interconnected structure.
I've been trying to pin down if there are some "quest files", but apparently no, and the quest is handled as a flow of chats, journal entries, inventory items and its usage, map and so on.