User defined categories in conformed dimension

Hi,
I am creating a conformed product dimension and one of the requirements is to let users create product categories for different reports. The list of products is retrieved from a source system. My initial solution was to just create new columns for each category but I think i will soon run of of columns in that case

Has any one encountered similar issues? Any help will be much appreciated.

Thanks
Syed

Use a separate data structure, most likely a parent/child hierarchy would be appropriate. Build an application to maintain it and treat the tables as separate from the DW. Use an ETL process to apply updates to a bridge table after the user has 'released' their changes.