How is XML defined?
XML is defined by a number of related specifications:
- Extensible Markup Language (XML) 1.0
Defines the syntax of XML. The XML specification is the primary focus of this article.
- XML Pointer Language (XPointer) and XML Linking Language (XLink)
Defines a standard way to represent links between resources. In addition to simple links, XML has mechanisms for links between multiple resources and links between read-only resources. XPointer describes how to address a resource, XLink describes how to associate two or more resources.
- Extensible Style Language (XSL)
Defines the standard stylesheet language for XML.
As time goes on, additional requirements will be addressed by other specifications. Currently (Sep, 1998), namespaces (dealing with tags from multiple tag sets), a query language (finding out what's in a document or a collection of documents), and a schema language (describing the relationships between tags, DTDs in XML) are all being actively pursued.