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The type xsd:ID is used for an attribute that uniquely identifies an element in an XML document. An xsd:ID value must be an NCName. This means that it must start with a letter or underscore, and can only contain letters, digits, underscores, hyphens, and periods.

xsd:ID carries several additional constraints:

  • Their values must be unique within an XML instance, regardless of the attribute's name or its element name.
  • A complex type cannot include more than one attribute of type xsd:ID, or any type derived from xsd:ID.
  • xsd:ID attributes cannot have default or fixed values specified.

Simple Type Information


Schema Document: datatypes.xsd


Type Inheritance Chain

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