After looking at the best way to implement the recently released schema.org Vocabularies, I decided to allow vocabularies to be included into other vocabularies. This would not only reduce repetition when specifying the same properties repeatedly, but would also allow vocabularies that include another vocabulary to be used in place of that vocabulary. It is used as follows:

class Thing < Mida::Vocabulary
  itemtype %r{http://example.com/vocab/thing}i
  has_one 'name', 'description'
end

class Book < Mida::Vocabulary
  itemtype %r{http://example.com/vocab/book}i
  include_vocabulary Thing
  has_one 'title', 'author'
end

class Collection < Mida::Vocabulary
  itemtype %r{http://example.com/vocab/collection}i
  has_many 'item' do
    extract Thing
  end
end

In the above if you gave a Book as an item of Collection this would be accepted because it includes the Thing vocabulary. When examining the item you would find #vocabulary set to Book and you would have access to all the properties of Thing and all the properties of Book.

This release also has a small bug fix so that mida no longer defaults to searches for %r{} and will only make searches if a type regexp is given.