Editing Kolmogorov complexity (section)

===Chain rule for Kolmogorov complexity===
{{Main| Chain rule for Kolmogorov complexity}}
The chain rule<ref>{{cite journal
  | first = A.
  | last = Zvonkin
  |author2=L. Levin
  | title = The complexity of finite objects and the development of the concepts of information and randomness by means of the theory of algorithms.
  | journal = Russian Mathematical Surveys
  | volume = 25
  | number = 6
  | pages = 83–124
  | year = 1970
  | doi = 10.1070/RM1970v025n06ABEH001269
 | bibcode = 1970RuMaS..25...83Z
 | s2cid = 250850390
 | url = http://alexander.shen.free.fr/library/Zvonkin_Levin_70.pdf}}</ref> for Kolmogorov complexity states that there exists a constant ''c'' such that for all ''X'' and ''Y'':

:''K''(''X'',''Y'') = ''K''(''X'') + ''K''(''Y''|''X'') + c*max(1,log(''K''(''X'',''Y''))).

It states that the shortest program that reproduces ''X'' and ''Y'' is [[Big-O notation|no more]] than a logarithmic term larger than a program to reproduce ''X'' and a program to reproduce ''Y'' given ''X''. Using this statement, one can define [[Mutual information#Absolute mutual information|an analogue of mutual information for Kolmogorov complexity]].