[feature request] Org as an Excerpt Database (or Multivalue Properties)

["Sven Bretfeld" <sven.bretfeld@gmx.ch>]

Hi all

Is it possible to give a property more than one value? 

I have an org file with a collection of citations and I want to give
them a number of keywords. For example:

* Ethics of a Hacker's Life
  :PROPERTIES:
  :author: Richard Stallmann
  :source: http://www.brainyquote.com/quotes/authors/r/richard_stallman.html
  :keywords:  money, code-writing, career, ethics
  :END:
  I could have made money this way, and perhaps amused myself writing
  code. But I knew that at the end of my career, I would look back on
  years of building walls to divide people, and feel I had spent my life
  making the world a worse place.

A property search for "code-writing" should match this citation and all
others with this property. An additional search for "career" should
narrow the matches down. But orgmode understands "money, ... ethics" as
ONE value, not FOUR. That's the problem.

Of course, this could be done with Tags, but with more than four or five
tags the line would become unreadable. It would also be possible to have
several properties "keyword_1: money", "keyword_2: code-writing" etc.
But then property searches would be useless (because sometimes you have
"money" as keyword_1, sometimes as keyword_2 or keyword_15).

*Why I consider this a worthwhile feature request:*

It is meant for authors or researchers. When I read something, I use to
make and collect excerpts of passages I find useful or interesting. When
writing an article or book, this excerpt-collection can be queried like
a database for certain keywords in order to find what you have read on
the topic. I think that many of us could use such a possibility. 

This should be a fairly easy thing to do with orgmode. Is there already
a module capable of doing what I want?

Thanks

Sven