For most purposes, the process hierarchy is the most convenient way to structure and use the documentation. However, it is sometimes useful to classify the documentation in other ways: for example, according to the contribution the process makes to the organization's quality objectives. This sort of additional classification can be superimposed on the basic process-oriented structure of the documentation.

This technique can be used for ISO 9000 and ISO 14000 accreditation, and for cross-functional initiatives and processes such as those relating to safety, health, environment, human resources, anti-discrimination, and the like.

This approach means that the organization can document all its processes - because it is good management practice to do so - without automatically exposing those processes to quality audit. The quality audit is restricted to those processes listed in the ISO 9000 cross-reference: that is, the processes that implement the organization's quality policy.