noun
contextually optional element
Technical computing term for an element that is optional depending on the context, such as in markup languages or configuration files.
XMLでは、文脈上の選択要素は状況に応じて省略できる。
In XML, contextually optional elements can be omitted depending on the situation.
Compound of 文脈 (context) + 上 (on, in terms of) + 選択 (selection, choice) + 要素 (element). The exact historical derivation is uncertain; the term is a modern technical coinage.