bnf.xsd

<?xml version='1.0' encoding="utf-8"?>
<xsd:schema
  xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
  xsi:schemaLocation='http://www.w3.org/2001/XMLSchema
                      http://www.w3.org/2001/XMLSchema.xsd'
  xmlns:xsd='http://www.w3.org/2001/XMLSchema'>

  <xsd:element name='bnf' type='BNFType'/>

  <xsd:complexType name='BNFType'>
    <xsd:sequence>
      <xsd:element name='section' type='SectionType' maxOccurs='unbounded'/>
    </xsd:sequence>
    <xsd:attribute name='version' type='VersionType' use='required'/>
    <xsd:attribute name='update' type='DateType' use='required'/>
  </xsd:complexType>

  <xsd:simpleType name='VersionType'>
    <xsd:restriction base='xsd:string'>
      <xsd:pattern value='\d+\.\d+'/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name='DateType'>
    <xsd:restriction base='xsd:string'>
      <xsd:pattern value='[1-3]?\d-[A-Z][a-z][a-z]-\d\d\d\d'/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name='SectionType'>
    <xsd:sequence>
      <xsd:element name='rule' type='RuleType' maxOccurs='unbounded'/>
    </xsd:sequence>
    <xsd:attribute name='id' type='SectionIDType' use='required'/>
  </xsd:complexType>

  <xsd:simpleType name='SectionIDType'>
    <xsd:restriction base='xsd:string'>
      <xsd:pattern value='[a-z]+(\.[a-z]+)*'/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name='RuleType'>
    <xsd:sequence>
      <xsd:element name='syntax' type='NonTerminalNameType'/>
      <xsd:element name='sequence' type='SequenceType'/>
    </xsd:sequence>
    <xsd:attribute name='issue' type='xsd:unsignedShort' use='optional'/>
  </xsd:complexType>

  <xsd:simpleType name='NonTerminalNameType'>
    <xsd:restriction base='xsd:string'>
      <xsd:pattern value='([_a-z])+(\-[_a-z]+)*'/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name='SequenceType'>
    <xsd:sequence>
      <xsd:element name='alternative' type='AlternativeType' maxOccurs='unbounded'/>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name='AlternativeType'>
    <xsd:choice maxOccurs='unbounded'>
      <xsd:element name='terminal' type='TerminalType'/>
      <xsd:element name='non-terminal' type='NonTerminalType'/>
    </xsd:choice>
    <xsd:attribute name='issue' type='xsd:unsignedShort' use='optional'/>
    <xsd:attribute name='note' type='xsd:string' use='optional'/>
  </xsd:complexType>

  <xsd:simpleType name='BooleanType'>
    <xsd:restriction base='xsd:string'>
      <xsd:enumeration value='true'/>
      <xsd:enumeration value='false'/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name='TerminalType'>
    <xsd:simpleContent>
      <xsd:extension base='xsd:string'>
        <xsd:attribute name='optional' type='BooleanType' default='false'/>
        <xsd:attribute name='sentence' type='BooleanType' default='false'/>
      </xsd:extension>
    </xsd:simpleContent>
  </xsd:complexType>

  <xsd:complexType name='NonTerminalType'>
    <xsd:simpleContent>
      <xsd:extension base='NonTerminalNameType'>
        <xsd:attribute name='optional' type='BooleanType' default='false'/>
      </xsd:extension>
    </xsd:simpleContent>
  </xsd:complexType>

</xsd:schema>