An important aspect of XML is that it allows a DTD to be shared across multiple documents. An XSL file provides a view into a specific set of tags defined in another XML document. The same XSL file can be applied to multiple XML documents, so long as the specifications of the tags are shared by each XML document. An XSL file, also known as a style sheet, contains the rules for selecting and presenting the data from its associated XML documents. If special handling is required for one of the tags defined in the XML document, a template is defined in the XSL file.
Commands exist for navigating both up and down the hierarchy.
XML is rapidly evolving into a robust programming language. What we're seeing is the introduction of yet another technology into our environment. Web developers have realized that they must provide their users with access to corporate data. This is a good thing. However, XML represents an entirely new standard developed to accommodate this requirement, including new techniques for describing data structures.