Extensible Markup Language: XML

2008 Oct 04

For conformity to the XML standard, an XML document must be well-formed and be valid. Related technologies:

Style Sheet Languages:
- CSS - Cascading Style Sheets (element by element)
- XSL - XML Style Language (is XML too) can reorder parts, is context sensitive and has two parts:
  - XSLT - XSL Transformation (can convert to HTML, or perl, ...),
    unlike CSS which only formats an element, XSLT can add or remove info
  - XSL-FO - Formatting Objects, page layout (not yet well supported),
    like Postcript (but without its Turing-complete programming language)
URL - Uniform Resource Locaters
URI - Uniform Resource Identifiers (superset of URL),
focus more on the resource and less on the location;
e.g. this is from book uri:isbn:0764547607
XLinks - to connect XML documents, includes XPointers which can link to internal parts of an XML doc with an A link.
Unicode character sets

Document Type Definition (DTD)

A DTD defines the tags used in an XML document. It is a vocubulary and syntax and specifies relations between elements and default values when no data is present or what fields are required. For example, MOL.DTD is what defines Chemical Markup Language (CML), or OFX is what defines Open Financial Exchange 2.0. An XML document defines structure and meaning. Formatting (appearance) is added with a style sheet.