searching and indexing weighted tags / catagory ratings, ideally in the plone catalog
===

My use case is that content objects can have weighted tags:

- ArticleA: java 5, mysql 3, php 1
- ArticleB: crypto 3, mysql 2
- ArticleC: plone 5, networking 1, security 4, agile 1
- ArticleD: plone4, mysql3, php 3
...

The list of tags is user extendible, the range of values is fixed to e.g. 1 - 5 

Now: how can I can I answer the following questions (ideally using portal_catalog):

- show all Articles that are tagged with java>2 and mysql>3
- whats the average value for mysql
- whats the highest rated plone Article?
- show all Articles that contain 'foobar' and are about plone

Possible solutions that come to my mind or were suggested so far are:

- go SQL
- create extra 'rating' content types that are indexed in a sperate catalog (pretty much like 
  references)
- encode the rating into 'java3', 'java4', 'java5', stick them into and KeywordIndex  and check if 
  AdvancedQuery can search them
- write a custom pluginindex

I guess though that others had the same task before. Any ideas on how to (best) move forward on this?