You should start by familiarizing yourself with Elgg's data model
http://learn.elgg.org/en/stable/guides/database.html#adding-reading-and-deleting-annotations
I'll check if I can find someone who likes to help me on this topic.
Next week I'll be together with my friends at http://www.opensource.co.at/ and I will ask them for their support (since I am no technical administrator, nor engineer or developer). :-)
Best Regards
Manfred
Using the Profile Manager plugin you can probably create the needed information. With the profile manager plugin you can extend specific profile fields and add rating type fields to enter amount of experience for example. https://github.com/ColdTrick/profile_manager
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