all, We're wanting to implement network wide categories.

Hi all,

We're wanting to implement network wide categories. The idea is:

1) All shops have a basic set of netowrk deinfed categories
2) the main blog uses these categories to allow visitors to navigate for products easier
3) individual shop owners can add their own cateogries if they wish.

We found this site which seems to have the networkwide categories already:

http://www.comicsy.co.uk/

The links across the top are to the categories and each product in the category is on a shop somewhere on the network.

Any idea how this is acheived? Am I missing a big part of the configuration or something?

Thanks in advance.
Gavin