   <!-- DTD for XML Signatures
        http://www.w3.org/2000/09/xmldsig#
        Joseph Reagle $last changed 20001215$ -->


   <!--

   The following entity declarations enable external/flexible content in
   the Signature content model.

   #PCDATA emulates schema string; when combined with element types it
   emulates schema's mixed content type.

   %foo.ANY permits the user to include their own element types from
   other namespaces, for example:
     <!ENTITY % KeyValue.ANY '| ecds:ECDSAKeyValue'>
     ...
     <!ELEMENT ecds:ECDSAKeyValue (#PCDATA)  >

   -->

   <!ENTITY % Object.ANY ''>
   <!ENTITY % Method.ANY ''>
   <!ENTITY % Transform.ANY ''>
   <!ENTITY % SignatureProperty.ANY ''>
   <!ENTITY % KeyInfo.ANY ''>
   <!ENTITY % KeyValue.ANY ''>
   <!ENTITY % PGPData.ANY ''>
   <!ENTITY % X509Data.ANY ''>
   <!ENTITY % SPKIData.ANY ''>


   <!-- Start Core Signature declarations, these should NOT be altered -->

   <!ELEMENT Signature (SignedInfo, SignatureValue, KeyInfo?, Object*)  >
   <!ATTLIST Signature  
   	xmlns	CDATA	#FIXED 'http://www.w3.org/2000/09/xmldsig#'
   	Id  	ID	#IMPLIED >

   <!ELEMENT SignatureValue (#PCDATA) >
   <!ATTLIST SignatureValue  
             Id  ID      #IMPLIED>

   <!ELEMENT SignedInfo (CanonicalizationMethod, 
   	SignatureMethod,  Reference+)  >
   <!ATTLIST SignedInfo  
   	Id	 ID 	 #IMPLIED 
    >

   <!ELEMENT CanonicalizationMethod (#PCDATA %Method.ANY;)* > 
   <!ATTLIST CanonicalizationMethod 
   	Algorithm CDATA #REQUIRED > 

   <!ELEMENT SignatureMethod (#PCDATA|HMACOutputLength %Method.ANY;)* >
   <!ATTLIST SignatureMethod 
   	Algorithm CDATA #REQUIRED > 

   <!ELEMENT Reference (Transforms?, DigestMethod, DigestValue)  >
   <!ATTLIST Reference  
   	Id	ID	#IMPLIED
   	URI	CDATA	#IMPLIED
   	Type	CDATA	#IMPLIED>


   <!ELEMENT Transforms (Transform+)>

   <!ELEMENT Transform (#PCDATA|XPath %Transform.ANY;)* >
   <!ATTLIST Transform 
   	Algorithm    CDATA    #REQUIRED >

   <!ELEMENT XPath (#PCDATA) >

   <!ELEMENT DigestMethod (#PCDATA %Method.ANY;)* >
   <!ATTLIST DigestMethod  
   	Algorithm		CDATA	#REQUIRED >

   <!ELEMENT DigestValue  (#PCDATA)  >

   <!ELEMENT KeyInfo	(#PCDATA|KeyName|KeyValue|RetrievalMethod|
               X509Data|PGPData|SPKIData|MgmtData %KeyInfo.ANY;)* >
   <!ATTLIST KeyInfo  
   	Id	ID	 #IMPLIED >

   <!-- Key Information -->

   <!ELEMENT KeyName (#PCDATA) >
   <!ELEMENT KeyValue (#PCDATA|DSAKeyValue|RSAKeyValue %KeyValue.ANY;)* >
   <!ELEMENT MgmtData (#PCDATA) >

   <!ELEMENT RetrievalMethod (Transforms?) >
   <!ATTLIST RetrievalMethod
      URI	CDATA #REQUIRED 
      Type	CDATA #IMPLIED > 

   <!-- X.509 Data -->

   <!ELEMENT X509Data ((X509IssuerSerial | X509SKI | X509SubjectName |
                        X509Certificate)+ | X509CRL %X509Data.ANY;)>
   <!ELEMENT X509IssuerSerial (X509IssuerName, X509SerialNumber) >
   <!ELEMENT X509IssuerName (#PCDATA) >
   <!ELEMENT X509SubjectName (#PCDATA) >
   <!ELEMENT X509SerialNumber (#PCDATA) >
   <!ELEMENT X509SKI (#PCDATA) >
   <!ELEMENT X509Certificate (#PCDATA) >
   <!ELEMENT X509CRL (#PCDATA) >

   <!-- PGPData -->

   <!ELEMENT PGPData ((PGPKeyID, PGPKeyPacket?) | (PGPKeyPacket) %PGPData.ANY;) >
   <!ELEMENT PGPKeyPacket  (#PCDATA)  >
   <!ELEMENT PGPKeyID  (#PCDATA)  >

   <!-- SPKI Data -->

   <!ELEMENT SPKIData (SPKISexp %SPKIData.ANY;)  >
   <!ELEMENT SPKISexp  (#PCDATA)  >

   <!-- Extensible Content -->

   <!ELEMENT Object (#PCDATA|Signature|SignatureProperties|Manifest %Object.ANY;)* >
   <!ATTLIST Object  
   	Id	ID	#IMPLIED 
   	MimeType	CDATA	#IMPLIED 
   	Encoding	CDATA	#IMPLIED >

   <!ELEMENT Manifest (Reference+)  >
   <!ATTLIST Manifest  
   	Id	ID	#IMPLIED >

   <!ELEMENT SignatureProperties (SignatureProperty+)  >
   <!ATTLIST SignatureProperties  
   	Id	ID	 #IMPLIED  >

   <!ELEMENT SignatureProperty (#PCDATA %SignatureProperty.ANY;)* >
   <!ATTLIST SignatureProperty  
   	Target 	CDATA	 #REQUIRED
   	Id	ID	 #IMPLIED  >

   <!-- Algorithm Parameters -->

   <!ELEMENT HMACOutputLength (#PCDATA) >

   <!ELEMENT DSAKeyValue (P, Q, G, Y, J?, (Seed, PgenCounter)?) > 
   <!ELEMENT P (#PCDATA) >
   <!ELEMENT Q (#PCDATA) >
   <!ELEMENT G (#PCDATA) >
   <!ELEMENT Y (#PCDATA) >
   <!ELEMENT J (#PCDATA) >
   <!ELEMENT Seed (#PCDATA) >
   <!ELEMENT PgenCounter (#PCDATA) >

   <!ELEMENT RSAKeyValue (Modulus, Exponent) > 
   <!ELEMENT Modulus (#PCDATA) >
   <!ELEMENT Exponent (#PCDATA) >