associations...

You can always add an assignment table like this:

class Teacher < ActiveRecord::Base   belongs_to :location   has_many :qualifications

  # location_id end

class Location < ActiveRecord::Base   has_many :teachers end

class Qualification < ActiveRecord::Base   belongs_to :quality   belongs_to :user

  # teacher_id, quality_id end

class Quality < ActiveRecord::Base   has_many :qualifications end

User.location # New York User.qualifications # List of qualities