The evaporating cloud is one of the six thinking processes in the theory of constraints (TOC). The evaporating cloud (EC) – also referred to in the literature as "the cloud", or as a "conflict resolution diagram" – is a logical diagram representing a problem that has no obvious satisfactory solution.<!-- need peer-reviewed examples/refs. This is internally published. -->

The most commonly used of the TOC tools, the EC was designed to address conflict or dilemma situations (trade-off situations where there is no acceptable compromise) by diagramming the logic behind the conflict and methodically examining the assumptions behind the logic.

The evaporating cloud tool is intended to similarly "vapourize" difficult problems by resolving an underlying conflict.

:[Goldratt teaches] that every problem is a conflict, and that conflicts arise because we create them by believing at least one erroneous assumption. Thus, simply by thinking about the assumptions that enforce the existence of a conflict, we should be able to resolve any conflict by evaporating it with the power of our thinking.

Usage

thumb|The generic structure of an evaporating cloud diagram

Building a cloud

The EC has a set format with five boxes, labelled A, B, C, D and D’, where B and C both lead to the goal of A, D leads to B, and D’ leads to C, and D and D’ are in "conflict".

The boxes represent two opposing wants that represent the conflict (D, D’),

The lines or arrows connecting the nodes represent the rationale or causal assumptions that are used to link the nodes. When communicating the cloud, the arrows should be read as "in order to" or "because" or "so that". For example: "In order to achieve A we require B because there is no way we can have A without B." Or: "There is no way we can have D and have D’ (read as "D-prime") at the same time."

Clouds are "built" by filling in the appropriate boxes with statements about the situation. Both the wording of the statements and the sequence of filling the boxes can be important. Below is a guide to the recommended sequence and questions for building Day-to-day Conflict or Inner Dilemma clouds.

  1. Identify the type of problem (there are variations in the way the diagrams are constructed for different types of problems.)
  2. Write a storyline of this problem in a factual, objective way, even if the problem causes an emotional upset.
  3. Build the cloud.
  4. Check the logical statements of the cloud and make necessary corrections and upgrades.
  5. Surface the assumptions behind the logical connections to find the one that is supporting the conflict.