Any numeric value that can be represented as a decimal number.

In addition, the range of values that can be represented in an IEEE double precision (i.e., 64-bit) floating point number may be represented using scientific notation. Roughly that range is ±10⁻³²³ to ±10³⁰⁸.

To represent a number expressed in scientific notation, E notation, a variant of exponential notation, is used in the attribute value. A number is represented in exponential notation as a value between 1 and 10 (or -1 and -10) which is multiplied by ten raised to some integral power. When reading E notation, the letter E is read as times 10 to the power.

That is, the significand (sometimes called the mantissa) is written as a decimal number, followed by the letter E, followed by an integer exponent. The multiplication sign and the base itself (10) are implied. Either the significand or the exponent (or both) may be a negative number, in which case it should be preceded by a minus sign. There should be no whitespace separating the significand from the E from the exponent. E.g., 3×10⁸ can be expressed as 3E8.

Other examples of scientific notation include: 3E10 (the speed of light in centimetres per second)9.12E-31 (the mass of an electron in Kg)4E11 (estimated number of stars in our galaxy)-1.76E11 (electron charge to mass quotient in coulombs per Kg)

Either e or E may be used to separate the significand from the exponent, however these Guidelines recommend E be used both for consistency with other standards bodies and to avoid confusion with the mathematical constant e.

10進数を作る数値．

また，IEEE倍精度浮動小数点(64bit長)をとることもできる．例えば， ±10⁻³²³ から ±10³⁰⁸など．

科学的数値を評点する際，指数表現は，属性値と して記述される． 10進数による仮数部，続いて記号E，続いて指数 部がくる． 乗算記号と底(10)は省略される．仮数部と指数 部には負になるかもしれない．記号Eと指数部を 分けるために空白文字を入れる必要はない．例えば，3×10⁸ は 3E8と書かれる．

他の例として，以下のようなものがある． 3E10 (光の速度(cm/秒))9.12E-31 (電子の質量(kg))4E11 (銀河系にある恒星の数(推定値))-1.76E11 (電子の電荷(クローン))

仮数部と指数部を分ける記号はeまたは Eのどちらでもよいが，当ガイドラインでは Eを使うことを推奨する．これは，他の規格との 整合性を保ち，数学における定数との混同を避けるためである．