# Constraints for an XPath file enumerating all of the possible
# elements and attributes described by a W3C Schema expression.
# Note this expression has limitations (e.g. mixed content cannot
# be expressed).

# $Id: xpath.rnc,v 1.7 2005/05/31 02:24:57 G. Ken Holman Exp $

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datatypes d = "http://www.w3.org/2001/XMLSchema-datatypes"
namespace x = "urn:oasis:names:tc:ubl:schema:XPath-1.0"

start = 
   element x:XPath # container for all xpath information
   {
      attribute id { text }, #identification of instance as a resource
      e #cannot name the pattern "element" so use "e" for short
   }

e = element x:Element
   {
      # name information
      attribute name { d:Name },
      ( 
         attribute prefix { text },
         attribute uri { d:anyURI }?
      )?,
      # data type
      attribute type { d:Name },
      # cardinality
      attribute minOccurs { d:integer },
      attribute maxOccurs { d:integer | "unbounded" },
      # mixed content
      attribute text { "" }?,
      # attributes attached to the element
      element x:Attribute
      {
         attribute name { d:Name },
         attribute use { "optional" | "required" },
         attribute type { d:Name }
      }*,
      # element content
      e*,
      # this only exists if the named element is already in the ancestry
      attribute loop { d:Name }?
   }

# end of file