XML Model Glossary
union | Derivation of a simple type to restrict its values to a collection of   | 
  | simple data types  | 
unique | An identity constraint used to specify that an element or attribute value (or set  | 
  | of values) must be unique or null within a specified scope  | 
URI  | Uniform Resource Identifier. A string of characters which identifies an  | 
  | Internet resource  | 
XDR | |
  | file. It is a simplified XSD (or schema)  | 
XML | Extensible Markup Language. Used for structuring documents with self-  | 
  | describing tags in plain text format  | 
XML language | Language used to define the structure of an XML model. It can be Document  | 
  | Type Definition 1.0 or XML Schema Definition 1.0  | 
XPath | XML Path Language. A language to address parts of an XML document  | 
  | For more information on XPath, see XPath abbreviated syntax in  | 
  | section Defining an identity constraint selector, in chapter Building an XML  | 
  | model  | 
XSD | XML Schema Definition (or schema). An XML language defining the  | 
  | structure of an XML file. It supports namespaces and datatypes  | 
270 | PowerDesigner  |