Week 10: XML

eXtensive Markup Language:

• XML is a derivative of SGML used to give structure to online documents
• better suited for web based documents than SGML
• does not use a predetermined set of tags like HTML
• It's primary use is to allow the format of documents to be read across platforms - standard of rules
• XML can be used to describe the formats of many types of documents
• XML hierarchy:
• Document
• Entities
• Elements
• Attributes

• All of this tells the computer how the document is formatted 

• XML is the container in which the parts of the document are contained and clearly defines each one
• XML cross checks with the document type definition (DTD) and to tell it how all of these part relate to one another
•  DTD defines the structure of the document
• tags are determined by organizations with their own language that will fit their specific needs
• the tags clearly show the beginning and end of each element but say nothing of how the document is to be formatted.  This is the point of XML the data can be adapted to any format the user may desire

• XML catalogs - defines the format described by the entities in an XML document
• XML namespaces - allows for naming of elements and attributes 
• useful when the same name is used for elements by different codes

• XLINK, XPointer, XPath - ways of linking to paths of other documents contained on the web
• XML's way of hyperlinking

• Like HTML, XML has a stylesheet 
• XSLT - allows XML be turned into HTML - skips formatting language