How do you Validate a Top-Level Taxonomy?

My Governance and Taxonomy Workshops invest a great deal of time "proving" that the custom taxonomy being developed is valid.  How can you know if your taxonomy is valid?  The process is long and hard in practice (we often spend between four and eight hours on this step), but the concept is pretty simple.  So, here are a few "best practices" in validating your taxonomy.  Always remember that it is better to find problems on the white board than to find them after you've deployed!

1. The starting taxonomy has NO MORE THAN seven (7) top-level categories.  Neither six nor eight shall the counting of the categories be, but seven.  Count them, seven.  Can you get by with fewer?  I've seen valid taxonomies with as few as three categories, but never more than seven.
2. Everyone can easily recite the categories from memory.  If your top-level taxonomy doesn't come easily to mind, then people aren't going to remember it and "own" it.  If they don't own it, then they won't do it.  The fastest way to make your taxonomy fail is to come up with one that isn't easy for people to remember.
3. It makes sense.  When colleagues from across the company look at the taxonomy, do they say "Yes, that is who we are and what we do?"
4. It survives the "brainstorming test."  After an hour or two of brainstorming, has anyone been able to come up with a topic or idea that doesn't fit, doesn't have a home, or can't be associated with one "primary" category?
5. Are the categories stable?  Will the top-level categories withstand re-organizations, buyouts, the creation of new business units, and changes in marketing strategies?  If not, then the top-level taxonomy will become awkward and ultimately fail.
6. Can you find stuff?  Ultimately, the usefulness of a top-level taxonomy is whether or not a user can find the right information at the right time.  If not, then you may need to rethink your taxonomy.
7. Audiences, views and roles.  When the group reviews the top-level taxonomy, is it easy to see how information will tailored to the various audiences and roles?  As an example, the taxonomy category "Our Company" should display very different information for the CEO than it will for a guest visiting the company's Internet site.  Does the top-level taxonomy clearly help identify information that will be presented (or suppressed) for each audience and role?

The above list represents some of the more effective methods for validating the top-level taxonomy.  Remember, it is easy to establish a top-level taxonomy during SharePoint implementation, but it is very difficult and painful to change it afterward.  Inspect what you expect!