Editing XML (section)

== Key terminology ==
The material in this section is based on the XML [[Specification]]. This is not an exhaustive list of all the constructs that appear in XML; it provides an introduction to the key constructs most often encountered in day-to-day use.

;{{visible anchor|Character}}: An XML document is a string of ''characters''. [[Valid characters in XML#Characters allowed but discouraged|Every]] legal [[Unicode]] character (except Null) may appear in an (1.1) XML document (while some are discouraged).

;{{visible anchor|Processor and application}}: The ''processor'' analyzes the markup and passes structured information to an ''application''. The specification places requirements on what an XML processor must do and not do, but the application is outside its scope. The [[Process (computing)|processor]] (as the specification calls it) is often referred to colloquially as an ''XML [[Parsing|parser]]''.

;{{visible anchor|Markup and content}}: The characters making up an XML document are divided into ''markup'' and ''content'', which may be distinguished by the application of simple [[Phrase structure rules|syntactic rules]]. Generally, strings that constitute markup either begin with the character <code>&lt;</code> and end with a <code>></code>, or they begin with the character <code>&</code> and end with a <code>;</code>. Strings of characters that are not markup are content. However, in a [[CDATA]] section, the delimiters <code>&lt;![CDATA[</code> and <code>]]></code> are classified as markup, while the text between them is classified as content. In addition, whitespace before and after the outermost element is classified as markup.

;{{visible anchor|Tag}}: A ''tag'' is a markup construct that begins with <code>&lt;</code> and ends with <code>></code>. There are three types of tag:
:* ''start-tag'', such as <code>&lt;section></code>;
:* ''end-tag'', such as <code>&lt;/section></code>;
:* ''empty-element tag'', such as <code>&lt;line-break /></code>.

;{{visible anchor|Element}}: An ''element'' is a logical document component that either begins with a start-tag and ends with a matching end-tag or consists only of an empty-element tag. The characters between the start-tag and end-tag, if any, are the element's ''content'', and may contain markup, including other elements, which are called ''child elements''. An example is <code>&lt;greeting>Hello, world!&lt;/greeting></code>. Another is <code>&lt;line-break&nbsp;/></code>.

;{{visible anchor|Attribute}}: An ''attribute'' is a markup construct consisting of a [[name–value pair]] that exists within a start-tag or empty-element tag. An example is <code>&lt;img src="madonna.jpg" alt="Madonna" /></code>, where the names of the attributes are "src" and "alt", and their values are "madonna.jpg" and "Madonna" respectively. Another example is <code>&lt;step number="3">Connect A to B.&lt;/step></code>, where the name of the attribute is "number" and its value is "3". An XML attribute can only have a single value and each attribute can appear at most once on each element. In the common situation where a list of multiple values is desired, this must be done by encoding the list into a well-formed XML attribute{{efn-lr|i.e., embedded quote characters would be a problem}} with some format beyond what XML defines itself. Usually this is either a comma or semi-colon delimited list or, if the individual values are known not to contain spaces,{{efn-lr|A common example of this is [[CSS]] class or identifier names.}} a space-delimited list can be used. An example with space as a delimiter is <code>&lt;div class="inner greeting-box">Welcome!&lt;/div></code>, where the attribute "class" both has the value "inner greeting-box" and also indicates the two [[CSS]] class names "inner" and "greeting-box".

;{{visible anchor|XML declaration}}: XML documents may begin with an ''XML declaration'' that describes some information about themselves. An example is <code>&lt;?xml version="1.0" encoding="UTF-8"?></code>.