The Extensible Markup Language (XML) is a document describing language for structure information. If an XML document satisfies constraints in the specification it is called well-formed . With additional constraints XML document may be valid. A XML document is composed of entities that may refer to other entities. A document entity is the root of an XML document.

XML is a subset of the Standard Generalized Markup Language (SGML) for web. XML is simpler and easier to implement than SGML. Comparing to HTML, whose markup set and semantics are fixed, XML allows authors create new tags. The XML specification includes: (i) "Extensible Markup Language (XML) 1.0" which defines the XML syntax; (ii) "XML Pointer Language (XPointer)" and "XML Linking Language (XLink) which defines the links among resources; (iii) "Extensible Style Language (XSL)" defines the XML stylesheet language; and (iv) "XML Namespaces" defines the XML namespaces.

Snaml adapts the specification of XML and integrate it into a programming language. With the set of XML commands, Snaml can generate XML documents. You may think Snaml as an XML generator. The Snaml codes for XML document are programable, managable, and reusable. A XML example is:

__pi "xml 1.0"
_welcome "Welcome to the World of Snaml."
  _topic "Today I am going to discuss snake."
  topic_
  _content "Long, long ago, ..."
    _quote "From B.C. ..."
  content_
welcome_