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rfc:rfc3741

Network Working Group J. Boyer Request for Comments: 3741 PureEdge Solutions Category: Informational D. Eastlake 3rd

                                                              Motorola
                                                             J. Reagle
                                                                   W3C
                                                            March 2004
            Exclusive XML Canonicalization, Version 1.0

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

 Canonical XML specifies a standard serialization of XML that, when
 applied to a subdocument, includes the subdocument's ancestor context
 including all of the namespace declarations and attributes in the
 "xml:" namespace.  However, some applications require a method which,
 to the extent practical, excludes ancestor context from a
 canonicalized subdocument.  For example, one might require a digital
 signature over an XML payload (subdocument) in an XML message that
 will not break when that subdocument is removed from its original
 message and/or inserted into a different context.  This requirement
 is satisfied by Exclusive XML Canonicalization.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Terminology. . . . . . . . . . . . . . . . . . . . . . .  2
     1.2.  Applications . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Limitations. . . . . . . . . . . . . . . . . . . . . . .  5
 2.  The Need for Exclusive XML Canonicalization. . . . . . . . . .  5
     2.1.  A Simple Example . . . . . . . . . . . . . . . . . . . .  6
     2.2.  General Problems with re-Enveloping. . . . . . . . . . .  7
 3.  Specification of Exclusive XML Canonicalization. . . . . . . .  8
     3.1.  Constrained Implementation (non-normative) . . . . . . .  9
 4.  Use in XML Security. . . . . . . . . . . . . . . . . . . . . . 10
 5.  Security Considerations. . . . . . . . . . . . . . . . . . . . 12
     5.1.  Target Context . . . . . . . . . . . . . . . . . . . . . 12

Boyer, et al. Informational [Page 1] RFC 3741 Exclusive XML Canonicalization March 2004

     5.2.  'Esoteric' Node-sets . . . . . . . . . . . . . . . . . . 13
 6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     6.1.  Normative References . . . . . . . . . . . . . . . . . . 13
     6.2.  Informative References . . . . . . . . . . . . . . . . . 14
 7.  Acknowledgements (Informative) . . . . . . . . . . . . . . . . 14
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 16

1. Introduction

 The XML Recommendation [XML] specifies the syntax of a class of
 objects called XML documents.  The Namespaces in XML Recommendation
 [XML-NS] specifies additional syntax and semantics for XML documents.
 It is normal for XML documents and subdocuments which are equivalent
 for the purposes of many applications to differ in their physical
 representation.  For example, they may differ in their entity
 structure, attribute ordering, and character encoding.  The goal of
 this specification is to establish a method for serializing the XPath
 node-set representation of an XML document or subset such that:
    1. The node-set is minimally affected by any XML context which has
       been omitted.
    2. The canonicalization of a node-set representing well-balanced
       XML [XML-Fragment] will be unaltered by further applications of
       exclusive canonicalization.
    3. It can be determined whether two node-sets are identical except
       for transformations considered insignificant by this
       specification under [XML, XML-NS].
 An understanding of the Canonical XML Recommendation [XML-C14N] is
 required.
 The World Wide Web Consortium Recommendation corresponding to this
 RFC is at: http://www.w3.org/TR/xml-exc-c14n.  Errata are located at
 http://www.w3.org/2002/07/xml-exc-c14n-errata.

1.1. Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [Keywords].
 The XPath 1.0 Recommendation [XPath] defines the term node-set and
 specifies a data model for representing an input XML document as a
 set of nodes of various types (element, attribute, namespace, text,
 comment, processing instruction, and root).  The nodes are included
 in or excluded from a node-set based on the evaluation of an
 expression.  Within this specification and [XML-C14N], a node-set is

Boyer, et al. Informational [Page 2] RFC 3741 Exclusive XML Canonicalization March 2004

 used to directly indicate whether or not each node should be rendered
 in the canonical form (in this sense, it is used as a formal
 mathematical set).  A node that is excluded from the set is not
 rendered in the canonical form being generated, even if its parent
 node is included in the node-set.  However, an omitted node may still
 impact the rendering of its descendants (e.g., by affecting the
 namespace context of the descendants).
 A document subset is a portion of an XML document indicated by an
 XPath node-set that may not include all of the nodes in the document.
 As defined in [XPath] every node (e.g., element, attribute, and
 namespace), has exactly one parent, which is either an element node
 or the root node.  An apex node is an element node in a document
 subset having no element node ancestor in the document subset.  An
 orphan node is an element node whose parent element node is not in
 the document subset.  The output parent of an orphan node that is not
 an apex node is the nearest ancestor element of the orphan node that
 is in the document subset; an apex node has no output parent.  The
 output parent of a non-orphan node is the parent of the node.  An
 output ancestor is any ancestor element node in the document subset.
 For example given a document tree with three generations under the
 root node A and where capitalization denotes the node is in the
 document subset (A,E,G).
 Pictorial Representation:
   [diagram of nodes,
    http://www.w3.org/TR/xml-exc-c14n/exc-c14n.png]
 Textual Representation:
   A-+-b
     `-c-+-d
         `-E-+-f
             `-G
 The following characteristics apply:
  • A is an apex node, output parent of E, and output ancestor of

(E,G);

  • E is an orphan node and the output parent of G.
 An element E in a document subset visibly utilizes a namespace
 declaration, i.e., a namespace prefix P and bound value V, if E or an
 attribute node in the document subset with parent E has a qualified
 name in which P is the namespace prefix.  A similar definition

Boyer, et al. Informational [Page 3] RFC 3741 Exclusive XML Canonicalization March 2004

 applies for an element E in a document subset that visibly utilizes
 the default namespace declaration, which occurs if E has no namespace
 prefix.
 The namespace axis of an element contains nodes for all non-default
 namespace declarations made within the element as well as non-default
 namespace declarations inherited from ancestors of the element.  The
 namespace axis also contains a node representing the default
 namespace if it is not the empty string, whether the default
 namespace was declared within the element or by an ancestor of the
 element.  Any subset of the nodes in a namespace axis can be included
 in a document subset.
 The method of canonicalization described in this specification
 receives an InclusiveNamespaces PrefixList parameter, which lists
 namespace prefixes that are handled in the manner described by the
 Canonical XML Recommendation [XML-C14N].
 The exclusive canonical form of a document subset is a physical
 representation of the XPath node-set, as an octet sequence, produced
 by the method described in this specification.  It is as defined in
 the Canonical XML Recommendation [XML-C14N] except for the changes
 summarized as follows:
  • attributes in the XML namespace, such as xml:lang and xml:space

are not imported into orphan nodes of the document subset, and

  • namespace nodes that are not on the InclusiveNamespaces

PrefixList are expressed only in start tags where they are

       visible and if they are not in effect from an output ancestor
       of that tag.
 The term exclusive canonical XML refers to XML that is in exclusive
 canonical form.  The exclusive XML canonicalization method is the
 algorithm defined by this specification that generates the exclusive
 canonical form of a given XML document subset.  The term exclusive
 XML canonicalization refers to the process of applying the exclusive
 XML canonicalization method to an XML document subset.

1.2. Applications

 The applications of Exclusive XML Canonicalization are very similar
 to those for Canonical XML [XML-C14N].  However, exclusive
 canonicalization, or equivalent means of excluding most XML context,
 is necessary for signature applications where the XML context of
 signed XML will change.  This sort of change is typical of many
 protocol applications.

Boyer, et al. Informational [Page 4] RFC 3741 Exclusive XML Canonicalization March 2004

 Note that in the case of the SignedInfo element of [XML-DSig], the
 specification of an appropriate canonicalization method is the only
 technique available to protect the signature from insignificant
 changes in physical form and changes in XML context.

1.3. Limitations

 Exclusive XML Canonicalization has the limitations of Canonical XML
 [XML-C14N] plus two additional limitations as follows:
    1. The XML being canonicalized may depend on the effect of XML
       namespace attributes, such as xml:lang, xml:space, and xml:base
       appearing in ancestor nodes.  To avoid problems due to the
       non-importation of such attributes into an enveloped document
       subset, either they MUST be explicitly given in a node of the
       XML document subset being canonicalized where their effect is
       needed or which is an ancestor of the node where their effect
       is needed or they MUST always be declared with an equivalent
       value in every context in which the XML document subset will be
       interpreted.
    2. Applications that use the XML being canonicalized may depend on
       the effect of XML namespace declarations where the namespace
       prefix being bound is not visibly utilized.  An example would
       be an attribute whose value is an XPath expression and whose
       evaluation therefore depends upon namespace prefixes referenced
       in the expression.  Or, an attribute value might be considered
       a QName [XML-NS] by some applications, but it is only a
       string-value to XPath:
       <number xsi:type="xsd:decimal">10.09</number>.
    To avoid problems with such namespace declarations,
    o  the XML MUST be modified so that use of the namespace prefix
       involved is visible, or
    o  the namespace declarations MUST appear and be bound to the same
       values in every context in which the XML will be interpreted,
       or
    o  the prefixes for such namespaces MUST appear in the
       InclusiveNamespaces PrefixList.

2. The Need for Exclusive XML Canonicalization

 In some cases, particularly for signed XML in protocol applications,
 there is a need to canonicalize a subdocument in such a way that it
 is substantially independent of its XML context.  This is because, in
 protocol applications, it is common to envelope XML in various layers
 of message or transport elements, to strip off such enveloping, and

Boyer, et al. Informational [Page 5] RFC 3741 Exclusive XML Canonicalization March 2004

 to construct new protocol messages, parts of which were extracted
 from different messages previously received.  If the pieces of XML in
 question are signed, they need to be canonicalized in a way such that
 these operations do not break the signature but the signature still
 provides as much security as can be practically obtained.

2.1. A Simple Example

 As a simple example of the type of problem that changes in XML
 context can cause for signatures, consider the following document:
    <n1:elem1 xmlns:n1="http://b.example">
        content
    </n1:elem1>
 this is then enveloped in another document:
    <n0:pdu xmlns:n0="http://a.example">
       <n1:elem1 xmlns:n1="http://b.example">
           content
       </n1:elem1>
    </n0:pdu>
 The first document above is in canonical form.  But assume that
 document is enveloped as in the second case.  The subdocument with
 elem1 as its apex node can be extracted from this second case with an
 XPath expression such as:
  (//. | //@* | //namespace::*)[ancestor-or-self::n1:elem1]
 The result of applying Canonical XML to the resulting XPath node-set
 is the following (except for line wrapping to fit this document):
    <n1:elem1 xmlns:n0="http://a.example"
              xmlns:n1="http://b.example">
        content
    </n1:elem1>
 Note that the n0 namespace has been included by Canonical XML because
 it includes namespace context.  This change which would break a
 signature over elem1 based on the first version.

Boyer, et al. Informational [Page 6] RFC 3741 Exclusive XML Canonicalization March 2004

2.2. General Problems with re-Enveloping

 As a more complete example of the changes in canonical form that can
 occur when the enveloping context of a document subset is changed,
 consider the following document:
    <n0:local xmlns:n0="foo:bar"
              xmlns:n3="ftp://example.org">
       <n1:elem2 xmlns:n1="http://example.net"
                 xml:lang="en">
           <n3:stuff xmlns:n3="ftp://example.org"/>
       </n1:elem2>
    </n0:local>
 And the following which has been produced by changing the enveloping
 of elem2:
    <n2:pdu xmlns:n1="http://example.com"
            xmlns:n2="http://foo.example"
            xml:lang="fr"
            xml:space="retain">
       <n1:elem2 xmlns:n1="http://example.net"
                 xml:lang="en">
           <n3:stuff xmlns:n3="ftp://example.org"/>
       </n1:elem2>
    </n2:pdu>
 Assume an XPath node-set produced from each case by applying the
 following XPath expression:
  (//. | //@* | //namespace::*)[ancestor-or-self::n1:elem2]
 Applying Canonical XML to the node-set produced from the first
 document yields the following serialization (except for line wrapping
 to fit in this document):
    <n1:elem2 xmlns:n0="foo:bar"
              xmlns:n1="http://example.net"
              xmlns:n3="ftp://example.org"
              xml:lang="en">
        <n3:stuff></n3:stuff>
    </n1:elem2>

Boyer, et al. Informational [Page 7] RFC 3741 Exclusive XML Canonicalization March 2004

 However, although elem2 is represented by the same octet sequence in
 both pieces of external XML above, the Canonical XML version of elem2
 from the second case would be (except for line wrapping so it will
 fit into this document) as follows:
   <n1:elem2 xmlns:n1="http://example.net"
              xmlns:n2="http://foo.example"
              xml:lang="en"
              xml:space="retain">
        <n3:stuff xmlns:n3="ftp://example.org"></n3:stuff>
    </n1:elem2>
 Note that the change in context has resulted in lots of changes in
 the subdocument as serialized by the inclusive Canonical XML [XML-
 C14N].  In the first example, n0 had been included from the context
 and the presence of an identical n3 namespace declaration in the
 context had elevated that declaration to the apex of the
 canonicalized form.  In the second example, n0 has gone away but n2
 has appeared, n3 is no longer elevated, and an xml:space declaration
 has appeared, due to changes in context.  But not all context changes
 have effect.  In the second example, the presence at ancestor nodes
 of an xml:lang and n1 prefix namespace declaration have no effect
 because of existing declarations at the elem2 node.
 On the other hand, using Exclusive XML Canonicalization as specified
 herein, the physical form of elem2 as extracted by the XPath
 expression above is (except for line wrapping so it will fit into
 this document) as follows:
    <n1:elem2 xmlns:n1="http://example.net"
              xml:lang="en">
        <n3:stuff xmlns:n3="ftp://example.org"></n3:stuff>
    </n1:elem2>
 in both cases.

3. Specification of Exclusive XML Canonicalization

 The data model, processing, input parameters, and output data for
 Exclusive XML Canonicalization are the same as for Canonical XML
 [XML-C14N] with the following exceptions:
    1. Canonical XML applied to a document subset requires the search
       of the ancestor nodes of each orphan element node for
       attributes in the XML namespace, such as xml:lang and
       xml:space.  These are copied into the element node except if a
       declaration of the same attribute is already in the attribute
       axis of the element (whether or not it is included in the

Boyer, et al. Informational [Page 8] RFC 3741 Exclusive XML Canonicalization March 2004

       document subset).  This search and copying are omitted from the
       Exclusive XML Canonicalization method.
    2. The Exclusive XML Canonicalization method may receive an
       additional, possibly null, parameter InclusiveNamespaces
       PrefixList containing a list of namespace prefixes and/or a
       token indicating the presence of the default namespace.  All
       namespace nodes appearing on this list are handled as provided
       in Canonical XML [XML-C14N].
    3. A namespace node N with a prefix that does not appear in the
       InclusiveNamespaces PrefixList is rendered if all of the
       conditions are met:
       1. Its parent element is in the node-set, and
       2. it is visibly utilized by its parent element, and
       3. the prefix has not yet been rendered by any output ancestor,
          or the nearest output ancestor of its parent element that
          visibly utilizes the namespace prefix does not have a
          namespace node in the node-set with the same namespace
          prefix and value as N.
    4. If the token representing the default namespace is not present
       in InclusiveNamespaces PrefixList, then the rules for rendering
       xmlns="" are changed as follows.  When canonicalizing the
       namespace axis of an element E that is in the node-set, output
       xmlns="" if and only if all of the conditions are met:
       1. E visibly utilizes the default namespace (i.e., it has no
          namespace prefix), and
       2. it has no default namespace node in the node-set, and
       3. the nearest output ancestor of E that visibly utilizes the
          default namespace has a default namespace node in the node-
          set.  (This step for xmlns="" is necessary because it is not
          represented in the XPath data model as a namespace node, but
          as the absence of a namespace node; see  Section 4.7
          Propagation of Default Namespace Declaration in Document
          Subsets [XML-C14N].)

3.1. Constrained Implementation (non-normative)

 The following is a (non-normative) method for implementing the
 Exclusive XML Canonicalization method for many straightforward cases
 -- it assumes a well-formed subset and that if an element is in the
 node-set, so is all of its namespace axis; if the element is not in
 the subset, neither is its namespace axis.
    1. Recursively process the entire tree (from which the XPath
       node-set was selected) in document order starting with the
       root. (The operation of copying ancestor xml: namespace
       attributes into output apex element nodes is not done.)
    2. If the node is not in the XPath subset, continue to process its
       children element nodes recursively.

Boyer, et al. Informational [Page 9] RFC 3741 Exclusive XML Canonicalization March 2004

    3. If the element node is in the XPath subset then output the node
       in accordance with Canonical XML except for namespace nodes
       which are rendered as follows:
       1. ns_rendered is a copy of a dictionary, off the top of the
          state stack, of prefixes and their values which have already
          been rendered by an output ancestor of the namespace node's
          parent element.
       2. Render each namespace node if and only if all of the
          conditions are met:
          1. it is visibly utilized by the immediate parent element or
             one of its attributes, or is present in
             InclusiveNamespaces PrefixList, and
          2. its prefix and value do not appear in ns_rendered.
       3. Render xmlns="" if and only if all of the conditions are
          met:
          1. The default namespace is visibly utilized by the
             immediate parent element node, or the default prefix
             token is present in InclusiveNamespaces PrefixList, and
          2. the element does not have a namespace node in the node-
             set declaring a value for the default namespace, and
          3. the default namespace prefix is present in the dictionary
             ns_rendered.
       4. Insert all the rendered namespace nodes (including xmlns="")
          into the ns_rendered dictionary, replacing any existing
          entries.  Push ns_rendered onto the state stack and recurse.
       5. After the recursion returns, pop the state stack.

4. Use in XML Security

 Exclusive Canonicalization may be used as a Transform or
 CanonicalizationMethod algorithm in XML Digital Signature [XML-DSig]
 and XML Encryption [XML-Enc].
 Identifier:
      http://www.w3.org/2001/10/xml-exc-c14n#
      http://www.w3.org/2001/10/xml-exc-c14n#WithComments
 Just as with [XML-C14N] one may use the "#WithComments" parameter to
 include the serialization of XML comments.  This algorithm also takes
 an optional explicit parameter of an empty InclusiveNamespaces
 element with a PrefixList attribute.  The value of this attribute is
 a white space delimited list of namespace prefixes, and where
 #default indicates the default namespace, to be handled as per [XML-
 C14N].  The list is in NMTOKENS format (a white space separated
 list).  For example:

Boyer, et al. Informational [Page 10] RFC 3741 Exclusive XML Canonicalization March 2004

    <ds:Transform
       Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#">
       <ec:InclusiveNamespaces PrefixList="dsig soap #default"
           xmlns:ec="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    </ds:Transform>
 indicates the exclusive canonicalization transform, but that
 namespaces with prefix "dsig" or "soap" and default namespaces should
 be processed according to [XML-C14N].
    Schema Definition (expressed in [XML-schema]):
    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE schema
      PUBLIC "-//W3C//DTD XMLSchema 200102//EN"
             "http://www.w3.org/2001/XMLSchema.dtd"
     [
       <!ATTLIST schema xmlns:ec CDATA
                 #FIXED 'http://www.w3.org/2001/10/xml-exc-c14n#'>
       <!ENTITY ec 'http://www.w3.org/2001/10/xml-exc-c14n#'>
       <!ENTITY % p ''>
       <!ENTITY % s ''>
      ]>
    <schema xmlns="http://www.w3.org/2001/XMLSchema"
            xmlns:ec="http://www.w3.org/2001/10/xml-exc-c14n#"
            targetNamespace="http://www.w3.org/2001/10/xml-exc-c14n#"
            version="0.1" elementFormDefault="qualified">
      <element name="InclusiveNamespaces"
               type="ec:InclusiveNamespaces"/>
      <complexType name="InclusiveNamespaces">
         <attribute name="PrefixList" type="NMTOKENS"/>
      </complexType>
    </schema>
    DTD:
    <!ELEMENT InclusiveNamespaces    EMPTY >
    <!ATTLIST InclusiveNamespaces
       PrefixList    NMTOKENS    #REQUIRED >

Boyer, et al. Informational [Page 11] RFC 3741 Exclusive XML Canonicalization March 2004

5. Security Considerations

 This specification is used to serialize an XPath node-set under
 certain assumptions given in [XML-C14N] and this specification.
 Three such examples include:
 1. implementations of [XML-C14N] and this specification do not render
    an XML declaration;
 2. implementations of this specification only render attributes from
    the "XML" namespace (e.g., xml:lang, xml:space, and xml:base) when
    they are in the subset being serialized;
 3. implementations of this specification do not consider the
    appearance of a namespace prefix within an attribute value to be
    visibly utilized.
 While such choices are consistent with other XML specifications and
 satisfy the Working Group's application requirements it is important
 that an XML application carefully construct its transforms such that
 the result is meaningful and unambiguous in its application context.
 In addition to this section, the Limitations of this specification,
 the Resolutions of [XML-C14N], and the Security Considerations of
 [XML-DSig] should be carefully attended to.

5.1. Target Context

 The requirement of this specification is to satisfy applications that
 "require a method which, to the extent practical, excludes ancestor
 context from a canonicalized subdocument." Given a fragment being
 removed from its source instance, this specification satisfies this
 requirement by excluding from the fragment any context from its
 ancestors that is not utilized.  Consequently, a signature [XML-DSig]
 over that fragment will remain valid in its source context, removed
 from the source context, and even in a new target context.  However,
 this specification does not insulate the fragment against confused
 interpretation in a target context.
 For example, if the <Foo/> element is signed in its source instance
 of <Bar/><Foo/></Bar> and then removed and placed in the target
 instance <Baz xmlns="http://example.org/bar"/><Foo/></Baz>, the
 signature should still be valid, but won't be if <Foo/> is
 interpreted as belonging to the http://example.org/bar namespace:
 this is dependent on how nodes are processed.
 This specification does not define mechanisms of removing, inserting,
 and "fixing up" a node-set. (For an example of this sort of
 specification, see the processing required of Creating the Result
 Infoset (section 4.5) when an [XInclude] is performed.) Instead,
 applications must carefully specify the XML (i.e., source, fragment,

Boyer, et al. Informational [Page 12] RFC 3741 Exclusive XML Canonicalization March 2004

 and target) or define the node-set processing (i.e., removal,
 replacement, and insertion) with respect to default namespace
 declarations (e.g., xmlns="") and XML attributes (e.g., xml:lang,
 xml:space, and xml:base).

5.2. 'Esoteric' Node-sets

 Consider an application that might use this specification or [XML-
 C14N] to serialize a single attribute node.  An implementation of
 either specification will not emit a namespace declaration for that
 single attribute node.  Consequently, a "carefully constructed"
 transform should create a node-set containing the attribute and the
 relevant namespace declaration for serialization.
 This example is provided to caution that as one moves beyond well-
 formed [XML] and then well-balanced XML [XML-Fragment], it becomes
 increasingly difficult to create a result that "is meaningful and
 unambiguous in its application context."

6. References

6.1. Normative References

 [Keywords]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 [XML]          Extensible Markup Language (XML) 1.0 (Second Edition).
                T.  Bray, E.  Maler, J. Paoli, and C. M. Sperberg-
                McQueen.  W3C Recommendation, October 2000.  Available
                at http://www.w3.org/TR/2000/REC-xml-20001006
 [XML-C14N]     Boyer, J., "Canonical XML", RFC 3076, March 2001.
                Also a W3C Recommendation available at
                http://www.w3.org/TR/2001/REC-xml-c14n-20010315
 [XML-NS]       Namespaces in XML.  T.  Bray, D. Hollander, and A.
                Layman.  W3C Recommendation, January 1999.  Available
                at http://www.w3.org/TR/1999/REC-xml-names-19990114/
 [XML-schema]   XML Schema Part 1: Structures D. Beech, M. Maloney, N.
                Mendelsohn, and H. Thompson.  W3C Recommendation, May
                2001.  Available at http://www.w3.org/TR/2001/REC-
                xmlschema-2-20010502/
 [XPath]        XML Path Language (XPath) Version 1.0. J. Clark and S.
                DeRose.  W3C Recommendation, November 1999.  Available
                at http://www.w3.org/TR/1999/REC-xpath-19991116

Boyer, et al. Informational [Page 13] RFC 3741 Exclusive XML Canonicalization March 2004

6.2. Informative References

 [URI]          Berners-Lee, T., Fielding, R. and L. Masinter,
                "Uniform Resource Identifiers (URI): Generic Syntax",
                RFC 2396, August 1998.
 [XInclude]     XML Inclusions (XInclude) Version 1.0. J. Marsh, and
                D.  Orchad.  W3C Candidate Recommendation, February
                2002.  Available at http://www.w3.org/TR/2002/CR-
                xinclude-20020221/
 [XML-DSig]     Eastlake, D., Reagle, J. and D. Solo, "XML-Signature
                Syntax and Processing", RFC 3275, March 2002.
                Available at http://www.w3.org/TR/2002/REC-xmldsig-
                core-20020212/
 [XML-Enc]      XML Encryption Syntax and Processing.  D.  Eastlake,
                and J.  Reagle.  W3C Candidate Recommendation, March
                2002.  Available at http://www.w3.org/TR/2002/CR-
                xmlenc-core-20020304/
 [XML-Fragment] XML Fragment Interchange.  P. Grosso, and D.
                Veillard.  W3C Candidate Recommendation, February
                2001.  Available at http://www.w3.org/TR/2001/CR-xml-
                fragment-20010212

7. Acknowledgements (Informative)

 The following people provided valuable feedback that improved the
 quality of this specification:
  • Merlin Hughes, Baltimore
  • Thomas Maslen, DSTC
  • Paul Denning, MITRE
  • Christian Geuer-Pollmann, University Siegen
  • Bob Atkinson, Microsoft

Boyer, et al. Informational [Page 14] RFC 3741 Exclusive XML Canonicalization March 2004

Authors' Addresses

 John Boyer
 PureEdge Solutions Inc.
 4396 West Saanich Rd.
 Victoria, BC, Canada V8Z 3E9
 Phone: +1-888-517-2675
 EMail: jboyer@PureEdge.com
 Donald E. Eastlake 3rd
 Motorola
 155 Beaver Street
 Milford, MA 01757 USA
 Phone: +1-508-634-2066 (h)
        +1-508-786-7554 (w)
 EMail: Donald.Eastlake@motorola.com
 Joseph M. Reagle Jr., W3C
 Massachusetts Institute of Technology
 Laboratory for Computer Science
 NE43-350, 545 Technology Square
 Cambridge, MA 02139
 Phone: +1-617-258-7621
 EMail: reagle@mit.edu

Boyer, et al. Informational [Page 15] RFC 3741 Exclusive XML Canonicalization March 2004

Full Copyright Statement

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Boyer, et al. Informational [Page 16]

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