每项都包含一个细节元素、金额所应用到的账目以及金额本身（可负可正）。

Each entry contains a detail element, the account to which the amount is applied and the amount which can be positive or negative.

youdao

所有空元素必须使用xml空标记语法，在右括号前有一个结尾的正斜杠(例如，becomes)。

All empty elements must use the XML empty tag syntax with a trailing forward slash before the end bracket (for example, becomes).

youdao

最基本的XPath使用元素名和正斜杠。

Basic XPaths use element names and forward slashes.

youdao

So here, I'm going to have delta H, is just the sum for all the products of delta heat of formation right? Here I'm going to put together all the products. So this is a positive heat of formation.

所以这里△H就是所有生成物的,生成热的和,对吧？这里,我要把元素组合成所有这些,生成物，所以这里是正的生成热。

麻省理工公开课 - 热力学与动力学课程节选