Declaring a class within a module

Surveying work code (in a module called Surveyor, no less), trying to understand it. I ran across this section that contains a class within a module. Is this the same as including the module? If not, what is the advantage of doing it this way? Thanks. (BONUS POINTS: Why are we appending self to class, is that not already implied?) ``` module Surveyor class Common RAND_CHARS = [('a'..'z'), ('A'..'Z'), (0..9)].map{|r| r.to_a}.flatten.join OPERATORS = %w(== != < > <= >= =~) class << self def make_tiny_code(len = 10) if RUBY_VERSION < "1.8.7" (1..len).to_a.map{|i| RAND_CHARS[rand(RAND_CHARS.size), 1] }.join else len.times.map{|i| RAND_CHARS[rand(RAND_CHARS.size), 1] }.join end end def to_normalized_string(text) words_to_omit = %w(a be but has have in is it of on or the to when) col_text = text.to_s.gsub(/(<[^>]*>)|\n|\t/su, ' ') # Remove html tags col_text.downcase! # Remove capitalization col_text.gsub!(/\"|\'/u, '') # Remove potential problem characters col_text.gsub!(/\(.*?\)/u,'') # Remove text inside parens col_text.gsub!(/\W/u, ' ') # Remove all other non-word characters cols = (col_text.split(' ') - words_to_omit) (cols.size > 5 ? cols[-5..-1] : cols).join("_") end def equal_json_excluding_wildcards(a,b) return false if a.nil? or b.nil? a = a.is_a?(String) ? JSON.load(a) : JSON.load(a.to_json) b = b.is_a?(String) ? JSON.load(b) : JSON.load(b.to_json) deep_compare_excluding_wildcards(a,b) end def deep_compare_excluding_wildcards(a,b) return false if a.class != b.class if a.is_a?(Hash) return false if a.size != b.size a.each do |k,v| return false if deep_compare_excluding_wildcards(v,b[k]) == false end elsif a.is_a?(Array) return false if a.size != b.size a.each_with_index{|e,i| return false if deep_compare_excluding_wildcards(e,b[i]) == false } else return (a == "*") || (b == "*") || (a == b) end true end alias :normalize :to_normalized_string def generate_api_id UUIDTools::UUID.random_create.to_s end end end end ```