Syntax for allowed tags and attributes

I've been thinking about the way I'd like to specify allowed tags and their attributes. Specifying a comma-separated list of allowed tags is fine, but in order to specify allowed attributes you need to use KSES's array syntax, which is awfully verbose.

I'd like to use a CSS-like syntax with attribute names appearing in square brackets:

`a[href][rel], strong, em`

This could even be extended to support KSES's bizarre attribute value functionality:

`a[href="valueless:n"][rel][target], strong, em`

This is a concise syntax and should be familiar to anyone who's familiar with CSS selectors.

Thoughts?