Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
node type, which may occur anywhere in the document, intended to carry instructions to the application.
The Document Object Model is a cross-platform and language-independent convention for representing and interacting with objects in HTML, XHTML and XML documents. Aspects of the DOM may be addressed and manipulated within the syntax of the programming language in use...
as Node.PROCESSING_INSTRUCTION_NODE, and they can be used in XPath
XPath
XPath is a language for selecting nodes from an XML document. In addition, XPath may be used to compute values from the content of an XML document...
- Features :XQuery provides the means to extract and manipulate data from XML documents or any data source that can be viewed as XML, such as relational databases or office documents....
with the 'processing-instruction' command.
Syntax
An SGML processing instruction is enclosed within ''.
An XML processing instruction is enclosed within '', and contains a target and optionally some content, which is the node value, that cannot contain the sequence '?>'.
The XML Declaration at the beginning of an XML document (shown below) is not a processing instruction, however its similar syntax has often resulted in it being referred to as a processing instruction.
Examples
The most common use of a processing instruction is to request the XML document be rendered using a stylesheet using the 'xml-stylesheet' target, which was standardized in 1999. It can be used for both XSLT
XSLT
XSLT is a declarative, XML-based language used for the transformation of XML documents. The original document is not changed; rather, a new document is created based on the content of an existing one. The new document may be serialized by the processor in standard XML syntax or in another format,...
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
DocBook is a semantic markup language for technical documentation. It was originally intended for writing technical documents related to computer hardware and software but it can be used for any other sort of documentation....
XSLT stylesheets understand a number of processing instructions to override the default behaviour.
The Robot Exclusion Standard, also known as the Robots Exclusion Protocol or robots.txt protocol, is a convention to prevent cooperating web crawlers and other web robots from accessing all or part of a website which is otherwise publicly viewable. Robots are often used by search engines to...
