Exists method should be useful

ie.frame(:name, 'foo').exists?

adding src as a way of finding frames should also be useful
ie.frame(:src, /foo/).exists?


Iterators for frames would make it more compatible with the rest of the api
ie.frames.each do |f|

Originally reported on Rubyforge: http://rubyforge.org/tracker/index.php?func=detail&aid=1860&group_id=104&atid=1999