 The thinking here is that the non–value-adding steps are often preparatory or tidying up to the value-adding step and are closely associated with the person or machine/workstation that executes that value-adding step.Therefore, each vertical line is the "story" of a person or workstation whilst the horizontal line represents the "story" of the product being created.Value-stream mapping is a recognised method used as part of Lean Six Sigma methodologies.