Standard Generalised Markup Language (SGML)
SGML controls the formatting of electronic documents for publication, either as printed output or electronic display. XML (Extensible Markup Language) is sometimes referred to as 'next generation SGML', while HTML (Hyper Text Markup Language) is a subset of SGML.
The text of a document is divided into a number of elements and sub-elements, each of which is named and allocated a start and end tag, defined by paired angle brackets. Tag names can be single letters (e.g. <p> for paragraph), abbreviated words (e.g. <li> for list), single words (e.g. <title>) or several words run together without spaces (e.g. <publisherName>. The end tag has a forward slash before the tag name (e.g.</p>).
The actual data text sits between the start and end tags, for example:
<title>Demystifying metadata</title> <p>Text of the paragraph is typed here.</p>
The structure also contains sub-divisions of some elements, such as ordered (i.e. numbered) and unordered (e.g. bulleted) lists. Within the list element the actual list items are repeated instances of <li>; this is sometimes referred to as 'nesting'. For clarity, it is standard practice to use separate lines for each element and where one element contains sub-elements.
<ol> <li> 1. Apologies </li> <li> 2. Minutes of previous meeting. </li> <li> 3. Matters arising. </li> </ol>