multi to multi relationship with multiple business view.

Hi
i am new for dimensional modeling. we have a problem for our survey dimensional model design:

each question we have category, theme and sub-category.

each themes can only belong to one category, and different sub-categories can belong to more than one themes and vice versa (multi to multi relationship). the problems is different department can have different 'theme to sub-category' mapping rule.
for example:
for dep1 the theme - sub-category mapping is like this
theme1 subcat1
theme1 subcat2
theme2 subcat1

for dep 2 the theme - sub-category mapping is like this
theme1 subcat1
theme1 subcat2
theme3 subcat1

the dimension model should provide different 'theme - sub-category mapping' views to different departments. so in dep1's view, subcat1 belongs to theme1 and theme2 and for dep2 the subcat1 belongs to theme1 and theme3
we have at least 10 different departments they may all have different mapping rules on this.

i know we need to fix the multi to multi relationship in fact table, but i just don't know how to do it.

any help?
thanks
Howard