I was thinking - at the moment Calibre supports the concept of tags and you can have multiple tags associated with a book. I was wondering if this could be extended to assign a value to a particular tag instance? That would allow the tags to effectively be treated as dynamic fields extensible by the user, with tag name effectively becoming the field name. Leaving the value empty would make the tags work just as they currently do.
A possible extension to this idea might be to support extending the current search syntax to support items like:
Code:
tag:publishyear=1980
The main restriction I would see remaining in place is not being able to sort at the GUI level on tag values.
This might avoid ongoing requests for new meta-data fields.
Anyway just throwing this out as a thought - not to worried if it is not thought worth following up on.