XML & XML Schema

XML & XML Schema

1. What is XML?

   • Extensible Markup Language
     • Similar to HTML, but XML describes data - focus on what the data is
       • XML documents must have a root element
         • Child elements
           • Elements nested in elements
       • Attributes
         • Text strings in double quotes e.g. <input type = "hidden">
       • Well formed

2. Document Object Model (DOM)

   • The standard for accessing documents
     • Defines objects and properties of all XML elements
       • Defines methods (interface) to access them
       • get, change, add and delete XML elements
   • Simple XML
     • PHP built-in XML parser
       • One class: SimpleXMLElement
         • addAttribute(name, value)
         • addChild(name, [,value])
         • asXML([filename])
         • attributes()
         • children()
         • getName()

3. XML Namespaces

   • Uniquely identify collection of element type and attribute names
     • Prevent name conflict
       • Use prefixes
         • Need xmlns attribute to give prefix a qualified name

4. XML Schema

   • Describes structure of XML structure
     • Support data types, namespaces, regular expressions
       • <xs:schema>...</xs:schema>
     • Order indicators: define order of elements
       • <xs:all>
         • Any order
       • <xs:choice>
         • specifies either one child element or another
       • <xs:sequence>
         • Must appear in specific order

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