noun
notation declaration
Technical term in computing, used in contexts such as XML or markup languages to declare the notation of external data.
XMLでは、記法宣言を使って外部データの形式を指定できる。
In XML, you can specify the format of external data using a notation declaration.
Compound of 記法 (notation) and 宣言 (declaration), likely a calque from English 'notation declaration'.