def define_dimension(name, &block)
      add Schema::Builders::DimensionBuilder.new(self).build(name, &block)
    end
def define_dimension(name, &block)
      add Schema::Builders::DimensionBuilder.new(self).build(name, &block)
    end
Defines a dimension table named +name+ in this schema.

 For example:

    @schema.define_dimension(:date) do
      columns do
        date   :date
        year   :year
        string :month
        ...
      end

      natural_key :date
      null_record :id => 1, :month => "Unknown Month"
    end

 @see Chicago::Schema::Builders::DimensionBuilder
 @return [Chicago::Schema::Dimension] the defined dimension.