Sometimes the basic information of XPath and XQuery is organized in the process of learning. In the process of checking the information, it feels very painful, because the information in mainland is too small. After using it, I want to put it and put it. It is better to hang it online. Personally hope to hang more information in this regard. If there is time, I will translate XQuery's norms - just for your convenience. XPath Query Language 1. XPath Introduction XPath is also created by W3C. In the W3C specification, the description of XPath 1.0 is this: "XPath 1.0 is a common syntax and semantic result of the common function of XSLT and XPointer. The main purpose of xpath is to find an XML document. Address. To support this main purpose, it also provides some basic functions for manipulating strings, numerical and Boolean values. XPath uses a compact, non-XML syntax to facilitate the use of XPath in the URI and XML properties. XPath operates on an abstraction of the XML document, not on its surface syntax. XPath is named in the hierarchy of an XML document because the path representation similar to the URL is used. "In addition to being used, XPath is also designed to include a natural subset that can be used to match (testing a node and a style matching), this method of XPath is defined in the XSLT specification." Xpath, you have to start with XSLT. Since the time, people are required to separate the contents of the data and the data, and the way to achieve this purpose is to format and use data using a general markup language. In this regard, W3C starts to design DSSSL (Document Style Semantics and Specification Language) specification, DSSSL is originally designed to work with SGML, however, unfortunately, SGML is not popular. After the XML is popular, W3c creates XSL (Extensible Stylesheet Language) to format XML, but XSL itself is too complicated, which greatly limits its use, and now the big software companies are formatted using CSS. XML. However, there is a part in XSL is useful, that is, XSLT (Extensible Stylesheet Language Transformations), XSLT enables users to easily access data in the XML document, and convert them into another format, such as HTML format Document. Because you can use XSLT to convert an XML document to another structure or an XML document containing additional data, you can convert XML to a normal text file or an RTF file or even a JavaScript file, in fact, you can convert to any document you want format. Here, XSLT exhibits its powerful power that can process XML data without complicating programming. You only need to create an XSLT processor and give the remaining things to this processor. For this reason, XSLT succeeded and eventually detached from the XSL specification. When W3C starts to create XSLT 1.0, they immediately realize that people use simple path expressions to access data in XML documents, so XPath 1.0 is born. XPath 1.0 is the core of XSLT 1.0. In fact, these two specifications have become the recommended standards for W3C on the same day (November 6, 1999). The XPath 1.0 can be separated from XSLT 1.0 and becomes a specification because W3C realizes that many other XML specifications need to address access to each part of the document.
