JIS X 0138-1:2004 ＣＡＳＥデータ交換形式－ＣＤＩＦ転送形式－第１部：構文及び符号化の一般規則 | ページ 4

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X 0138-1 : 2004 (ISO/IEC 15475-1 : 2002)
               repeated any number of times. If the ellipsis appears immediately after a
              closing brace "}]", then it applies to the portion of the formula enclosed
               between that closing brace and the corresponding opening brace "[{".
              If an ellipsis appears after any other element, then it applies only to that
                  element.
!!           Introduces normal English text. This is used when the definition of a
                syntactic element is not expressed in BNF.
               Spaces are used to separate syntactic elements. Multiple spaces and line
               breaks are treated as a single space. Apart from those symbols to which
              special functions were given above, other characters and character strings in
              a formula stand for themselves. In addition, if the symbols to the right of the
              definition operator in a production consist entirely of BNF symbols, then
               those symbols stand for themselves and do not take on their special
                  meaning.
Pairs of braces and square brackets may be nested to any depth, and the alternative operator may appear at
any depth within such a nest.
A character string that forms an instance of any syntactic element may be generated from the BNF definition of
that syntactic element by application of the following steps:
a)   elect any one option from those defined in the right hand side of a production rule for the
  element, and replace the element with this option.
b)   eplace each ellipsis and the object to which it applies with one or more instances of that object.
c)   or every portion of the string enclosed in square brackets, either delete the brackets and their
  contents or change the brackets to braces.
d)   or every portion of the string enclosed in braces, apply steps a)   hrough e)   o the substring
  between the braces, then remove the braces.
e)   pply steps a)   hrough e)   o any non-terminal syntactic element (i.e., name enclosed in angle
  brackets)   hat remains in the string.
The expansion or production is complete when no further non-terminal symbols remain in the character string.