With the current interest in visualisation (of data, issues and processes), it’s worth reminding ourselves of the pioneering work done in the 1960s by Brian Lewis, Ivan Horabin and others, who developed flow chart versions of complex rules and regulations they called ‘algorithms’, or often ‘ordinary language algorithms’ to distinguish them from computer programmes. Two good sources are

  • Brian Lewis, Ivan Horabin, and Chris Gane (1967) Flow charts, logical trees and algorithms for rules and regulations. London: HMSO.
  • Ivan Horabin, and Brian Lewis (1978). Algorithms. Englewood Cliffs, NJ: Educational Technology Publications.


They list 5 key characteristics of algorithms, which I think we’d do well to apply to any design approach to complex information:

  1. You need only read those parts of the algorithm relevant to the specific problem you are faced with solving.
  2. You need only read each part once.
  3. You do not have to remember prior decisions made in the algorithm.
  4. The language of each part is simple.
  5. You are confident that you have the right answer at each step and at the conclusion.


Here’s a before-and-after from a 1966 tax letter sent to several million UK taxpayers:


If the asset consists of stocks or shares which have values quoted or a stock exchange (see also paragraph G below), or unit trust units whose values are regularly quoted, the gain or loss (subject to expenses accruing after 6 April 1965, is the difference between the amount you received on disposal and the market value on 6 April 1965, except that in the case of a gain where the actual cost of the asset was higher than the value at 6 April 1965, the chargeable gain is the excess of the amount you received on disposal over the original cost or acquisition price; and in the case of a loss, where the actual cost of the asset was lower than the value of 6 April 1965, the allowable loss is the excess of the original cost or acquisition price over the amount received on disposal.

If the substitution of original cost for the value at 6 April 1965, turns a gain into a loss, or a loss into a gain, there is, for the purpose of tax, no chargeable gain or allowable loss.

Their version:

diagram of complex tax rules