XML basic concepts: XPath, XSLT, XQuery, and xqueryx

XML involves a series of technical specifications and related technologies, with many and complex concepts. Here, we will briefly introduce four concepts: XPath, XSLT, XQuery, and xqueryx, which are W3C specifications.

XPath is the XML Path Language. XPath provides general syntax and semantics for locating and linking information in an XML document. It is an expression language that can be used to easily identify nodes in XML documents. XPath is designed to be used by other standards, such as XSLT and XQuery.

XSLT: Extensible Stylesheet Language transformations. It is a W3C recommendation standard and is mainly used to convert XML documents into XHTML documents or other XML documents. XSLT is used to format XML documents, just like CSS is used to HTML.

XQuery is the XML query language. XQuery is like SQL language in relational databases. XQuery is actually integrated into three languages:
(1) The surface syntax is the easiest language to see and most likely accessible to users. In many aspects, the language version is XQuery.
(2) XML-based alternative syntax replaces xqueryx with a language that is easier for machine processing ).
(3) The formal algebra language describes the XQuery processing in detail. ProgramInternal working mechanism.

Xqueryx, that is, XML syntax for XQuery. It is an XML-based syntax specification that replaces the surface language and is one of the files that have been added to the XQuery archive family earlier. It mainly provides an XML syntax for computer processing.
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