By the Numbers

Richard Wilhelm

Form and Style Describes Use of the Modified Decimal Numbering System

Properly organizing the sections of your standard is a crucial part of the standards development process. While the entire Form and Style for ASTM Standards manual is an aid in achieving this order, Part D, Use of the Modified Decimal Numbering System, specifically addresses the means by which information is organized in a standard. Following the rules of Part D will result in standards that flow well and are more easily understood by users.

According to Part D's introduction, ASTM International adopted the use of the modified decimal numbering system in 1963. Using the MDN system, each division in a standard is assigned a unique number that shows the relationship of that section to all previous sections.

Section D2 advises that standards writers should not use a combination of the MDN system and other numbering systems. For example, 8.4 would not be divided into subsections 8.4 (a) and 8.4 (b); instead these would become 8.4.1 and 8.4.2.

Each standard consists of primary sections, which may include one or more secondary sections. In turn, secondary sections may include ternary sections, which, finally, may include quaternary sections. Here is what this arrangement looks like:

1. (primary section)

1.1 (secondary section)

1.1.1 (ternary section) (quaternary section)

Details on the assignment of numbers in the main body of the standard using the MDN system are given in D3. A preliminary section such as a foreword or introduction should not be assigned a number, so that the scope of the standard can be designated with the number "1."

Section D also explains how other parts of a standard should be numbered. These include the following:

  • Supplementary Requirements (D4). Each such requirement is numbered with the letter S followed by a consecutive number, beginning with 1.
  • Literature References (D5). Where a document includes five or more literature references, list them in an unnumbered section at the end of the document, preceding annexes and appendixes. Section G21 of Form and Style provides more information.
  • Annexes and Appendixes (D6). Precede the title of each annex (mandatory information placed outside the body of the standard) by the letter A, followed by a number in consecutive order, beginning with 1. Precede the title of each appendix (nonmandatory information placed outside the body of the standard) by the letter X, followed by a number in consecutive order, beginning with 1.
  • Equations (D7). Equations should be numbered when two or more are included in the main text. Equations are numbered with consecutive arabic numbers beginning with 1, in the order in which each appears.
  • Tables and Figures (D8 and D9). Tables and figures are assigned consecutive arabic numbers throughout the main text of the standard without regard to the number assigned to the section in which the table is referenced. Tables in annexes and appendixes are numbered by the designation of the annex or appendix, followed by consecutive numbers beginning with 1 (for example, Table A1.1 or X3.2). This is also how equations in annexes or appendixes would be designated.
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