Consider four basic types of documents—guides, practices, references, and specifications. The documents written by ASTM E07.03 on Penetrant and Magnetic Particle Methods have traditionally been guides, practices, and references. This subcommittee will now include specifications. Guides and practices instruct or guide the user, define good industry practices, and always give the user every possible option from which to select. They supply detailed how-to information to the user on how to apply the process. The references are a collection of graded anomalies that furnish the engineer with a very useful tool by which he can define acceptance criteria. A specification is a control document that establishes the basic parameters within which the process must be controlled. They are thou shall documents and supply very little howto information.
In order to call out guides and practices on an engineering drawing, in a specification, or in a contract, many qualifying statements are required, making these documents undesirable for this purpose. Specifications supply a minimum amount of instructions or how-to information—they define the parameters within which the process is applied or controlled. There are, basically, three types of specifications: (1) those that control the process, (2) those that establish the acceptance criteria, and (3) those that do both.