Adding an attribute to a ActiveRecord::Base instance

I have an instance of ActiveRecord::Base called Site. Is it possible to
add attributes to that class in code, like so

class Site < ActiveRecord::Base
belongs_to :user
attr_accessor :type_site_boolop, :type_program_boolop, :books_only

I don’t want those additional attributed in the DB. The problem is that
given

@site = Site.new
@site.type_site_boolop = ‘foo’

@site.attributes does not include type_site_boolop. Any ideas?

Thanks again, I’m new too Rails and this forum has been most helpful
already!

Felix