Only after syntax checking is passed, can an XML document be confirmed as well formed and can the logical structure of the document be parsed.
只有语法检查通过之后，才能确认XML文档格式良好并可以解析文档的逻辑结构。
2
Entities provide a logical name for a specific file that you want to include. The basic syntax of an external entity is.
实体为需要包含的特定文件提供一个逻辑名。
3
You can also use an XPath syntax to retrieve the contents of a message. The following Java code accesses the first chapter element in the logical tree using the XPath syntax.