Declare attribute to apply to any element

[herb plews]

I have an xml schema (w3c style), very complex, lots of elements, highly structured. Now I'm told to add a "private" attribute to every element. How do I do that without declaring it individually for every element? How do I define an attribute and declare that it may be used anywhere, for any element?

[herb plews]

Now don't everyone speak at once! Wait your turn, you'll all get a chance.

[herb plews]

Thanks everyone, for the overwhelming response.

(What a lame forum.)