XML Information Set in Brief
  - 
    data model for tree of elements with attributes
    
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	largely implicit in the XML 1.0 spec
      
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	motivated by questions from DOM development
    
 
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    named properties: children, base URI, etc.
    
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	provides shared terminology for future specs
    
 
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    other specs (e.g. XML Schema) may refine this model with other properties