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Network Working Group                                           E. WildeRequest for Comments: 5147                                   UC BerkeleyUpdates:2046                                                  M. DuerstCategory: Standards Track                       Aoyama Gakuin University                                                              April 2008URI Fragment Identifiers for the text/plain Media TypeStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   This memo defines URI fragment identifiers for text/plain MIME   entities.  These fragment identifiers make it possible to refer to   parts of a text/plain MIME entity, either identified by character   position or range, or by line position or range.  Fragment   identifiers may also contain information for integrity checks to make   them more robust.Wilde & Duerst              Standards Track                     [Page 1]

RFC 5147            text/plain Fragment Identifiers           April 2008Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .31.1.  What Is text/plain?  . . . . . . . . . . . . . . . . . . .31.2.  What Is a URI Fragment Identifier? . . . . . . . . . . . .41.3.  Why text/plain Fragment Identifiers? . . . . . . . . . . .41.4.  Incremental Deployment . . . . . . . . . . . . . . . . . .51.5.  Notation Used in This Memo . . . . . . . . . . . . . . . .52.  Fragment Identification Methods  . . . . . . . . . . . . . . .52.1.  Fragment Identification Principles . . . . . . . . . . . .62.1.1.  Positions and Ranges . . . . . . . . . . . . . . . . .62.1.2.  Characters and Lines . . . . . . . . . . . . . . . . .72.2.  Combining the Principles . . . . . . . . . . . . . . . . .72.2.1.  Character Position . . . . . . . . . . . . . . . . . .72.2.2.  Character Range  . . . . . . . . . . . . . . . . . . .82.2.3.  Line Position  . . . . . . . . . . . . . . . . . . . .82.2.4.  Line Range . . . . . . . . . . . . . . . . . . . . . .82.3.  Fragment Identifier Robustness . . . . . . . . . . . . . .83.  Fragment Identification Syntax . . . . . . . . . . . . . . . .93.1.  Integrity Checks . . . . . . . . . . . . . . . . . . . . .94.  Fragment Identifier Processing . . . . . . . . . . . . . . . .104.1.  Handling of Line Endings in text/plain MIME Entities . . .104.2.  Handling of Position Values  . . . . . . . . . . . . . . .114.3.  Handling of Integrity Checks . . . . . . . . . . . . . . .114.4.  Syntax Errors in Fragment Identifiers  . . . . . . . . . .125.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .126.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .137.  Security Considerations  . . . . . . . . . . . . . . . . . . .138.  References . . . . . . . . . . . . . . . . . . . . . . . . . .148.1.  Normative References . . . . . . . . . . . . . . . . . . .148.2.  Informative References . . . . . . . . . . . . . . . . . .14Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . .16Wilde & Duerst              Standards Track                     [Page 2]

RFC 5147 text/plain Fragment Identifiers April 20081. Introduction This memo updates the text/plain media type defined inRFC 2046 [3] by defining URI fragment identifiers for text/plain MIME entities. This makes it possible to refer to parts of a text/plain MIME entity. Such parts can be identified by either character position or range, or by line position or range. Integrity checking information can be added to a fragment identifier to make it more robust, enabling applications to detect changes of the entity. This section gives an introduction to the general concepts of text/ plain MIME entities and URI fragment identifiers, and it discusses the need for fragment identifiers for text/plain and deployment issues.Section 2 discusses the principles and methods on which this memo is based.Section 3 defines the syntax, andSection 4 discusses processing of text/plain fragment identifiers.Section 5 shows some examples.1.1. What Is text/plain? Internet Media Types (often referred to as "MIME types"), as defined inRFC 2045 [2] andRFC 2046 [3], are used to identify different types and sub-types of media.RFC 2046 [3] andRFC 3676 [6] specify the text/plain media type, which is used for simple, unformatted text. Quoting fromRFC 2046 [3]: "Plain text does not provide for or allow formatting commands, font attribute specifications, processing instructions, interpretation directives, or content markup. Plain text is seen simply as a linear sequence of characters, possibly interrupted by line breaks or page breaks". The text/plain media type does not restrict the character encoding; any character encoding may be used. In the absence of an explicit character encoding declaration, US-ASCII [13] is assumed as the default character encoding. This variability of the character encoding makes it impossible to count characters in a text/plain MIME entity without taking the character encoding into account, because there are many character encodings using more than one octet per character. The biggest advantage of text/plain MIME entities is their ease of use and their portability among different platforms. As long as they use popular character encodings (such as US-ASCII or UTF-8 [12]), they can be displayed and processed on virtually every computer system. The only remaining interoperability issue is the representation of line endings, which is discussed inSection 4.1.Wilde & Duerst Standards Track [Page 3]

RFC 5147 text/plain Fragment Identifiers April 20081.2. What Is a URI Fragment Identifier? URIs are the identification mechanism for resources on the Web. The URI syntax specified inRFC 3986 [7] optionally includes a so-called "fragment identifier", separated by a number sign ('#'). The fragment identifier consists of additional reference information to be interpreted by the user agent after the retrieval action has been successfully completed. The semantics of a fragment identifier are a property of the data resulting from a retrieval action, regardless of the type of URI used in the reference. Therefore, the format and interpretation of fragment identifiers is dependent on the media type of the retrieval result. The most popular fragment identifier is defined for text/html (defined inRFC 2854 [10]) and makes it possible to refer to a specific element (identified by the value of a 'name' or 'id' attribute) of an HTML document. This makes it possible to reference a specific part of a Web page, rather than a Web page as a whole.1.3. Why text/plain Fragment Identifiers? Referring to specific parts of a resource can be very useful because it enables users and applications to create more specific references. Users can create references to the part they really are interested in or want to talk about, rather than always pointing to a complete resource. Even though it is suggested that fragment identification methods are specified in a media type's MIME registration (see [15]), many media types do not have fragment identification methods associated with them. Fragment identifiers are only useful if supported by the client, because they are only interpreted by the client. Therefore, a new fragment identification method will require some time to be adopted by clients, and older clients will not support it. However, because the URI still works even if the fragment identifier is not supported (the resource is retrieved, but the fragment identifier is not interpreted), rapid adoption is not highly critical to ensure the success of a new fragment identification method. Fragment identifiers for text/plain, as defined in this memo, make it possible to refer to specific parts of a text/plain MIME entity, using concepts of positions and ranges, which may be applied to characters and lines. Thus, text/plain fragment identifiers enable users to exchange information more specifically, thereby reducing the time and effort that is necessary to manually search for the relevant part of a text/plain MIME entity.Wilde & Duerst Standards Track [Page 4]

RFC 5147            text/plain Fragment Identifiers           April 2008   The text/plain format does not support the embedding of links, so in   most environments, text/plain resources can only serve as targets for   links, and not as sources.  However, when combining the text/plain   fragment identifiers specified in this memo with out-of-line linking   mechanisms such as XLink [14], it becomes possible to "bind" link   resources to text/plain resources and thereby "embed" links into   text/plain resources.  Thus, the text/plain fragment identifiers   specified in this memo open a path for text/plain files to become   bidirectionally navigable resources in hypermedia systems such as the   Web.1.4.  Incremental Deployment   As long as text/plain fragment identifiers are not supported   universally, it is important to consider the implications of   incremental deployment.  Clients (for example, Web browsers) not   supporting the text/plain fragment identifier described in this memo   will work with URI references to text/plain MIME entities, but they   will fail to locate the sub-resource identified by the fragment   identifier.  This is a reasonable fallback behavior, and in general,   users should take into account the possibility that a program   interpreting a given URI will fail to interpret the fragment   identifier part.  Since fragment identifier evaluation is local to   the client (and happens after retrieving the MIME entity), there is   no reliable way for a server to determine whether a requesting client   is using a URI containing a fragment identifier.1.5.  Notation Used in This Memo   The capitalized 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 inRFC2119 [4].2.  Fragment Identification Methods   The identification of fragments of text/plain MIME entities can be   based on different foundations.  Since it is not possible to insert   explicit, invisible identifiers into a text/plain MIME entity (for   example, as used in HTML documents, implemented through dedicated   attributes), fragment identification has to rely on certain inherent   properties of the MIME entity.  This memo specifies fragment   identification using four different methods, which are character   positions and ranges, and line positions and ranges, augmented by an   integrity check mechanism for improving the robustness of fragment   identifiers.Wilde & Duerst              Standards Track                     [Page 5]

RFC 5147            text/plain Fragment Identifiers           April 2008   When interpreting character or line numbers, implementations MUST   take the character encoding of the MIME entity into account, because   character count and octet count may differ for the character encoding   being used.  For example, a MIME entity using the UTF-16 encoding (as   specified inRFC 2781 [11]) uses two octets per character in most   cases, and sometimes four octets per character.  It can also have a   leading BOM (Byte-Order Mark), which does not count as a character   and thus also affects the mapping from a simple octet count to a   character count.2.1.  Fragment Identification Principles   Fragment identification can be done by combining two orthogonal   principles, which are positions and ranges, and characters and lines.   This section describes the principles themselves, whileSection 2.2   describes the combination of the principles.2.1.1.  Positions and Ranges   A position does not identify an actual fragment of the MIME entity,   but a position inside the MIME entity, which can be regarded as a   fragment of length zero.  The use case for positions is to provide   pointers for applications that may use them to implement   functionalities such as "insert some text here", which needs a   position rather than a fragment.  Positions are counted from zero;   position zero being before the first character or line of a text/   plain MIME entity.  Thus, a text/plain MIME entity having one   character has two positions, one before the first character (position   zero), and one after the first character (position 1).   Since positions are fragments of length zero, applications SHOULD use   other methods than highlighting to indicate positions, the most   obvious way being the positioning of a cursor (if the application   supports the concept of a cursor).   Ranges, on the other hand, identify fragments of a MIME entity that   have a length that may be greater than zero.  As a general principle   for ranges, they specify both a lower and an upper bound.  The start   or the end of a range specification may be omitted, defaulting to the   first or last position of the MIME entity, respectively.  The end of   a range must have a value greater than or equal to the start.  A   range with identical start and end is legal and identifies a range of   length zero, which is equivalent to a position.   Applications that support a concept such as highlighting SHOULD use   such a concept to indicate fragments of lengths greater than zero to   the user.Wilde & Duerst              Standards Track                     [Page 6]

RFC 5147            text/plain Fragment Identifiers           April 2008   For positions and ranges, it is implicitly assumed that if a number   is greater than the actual number of elements in the MIME entity,   then it is referring to the last element of the MIME entity (seeSection 4 for details).2.1.2.  Characters and Lines   The concept of positions and ranges can be applied to characters or   lines.  In both cases, positions indicate points between these   entities, while ranges identify zero or more of these entities by   indicating positions.   Character positions are numbered starting with zero (ignoring initial   BOM marks or similar concepts that are not part of the actual textual   content of a text/plain MIME entity), and counting each character   separately, with the exception of line endings, which are always   counted as one character (seeSection 4.1 for details).   Line positions are numbered starting with zero (with line position   zero always being identical with character position zero);Section 4.1 describes how line endings are identified.  Fragments   identified by lines include the line endings, so applications   identifying line-based fragments MUST include the line endings in the   fragment identification they are using (e.g., the highlighted   selection).  If a MIME entity does not contain any line endings, then   it consists of a single (the first) line.2.2.  Combining the Principles   In the following sections, the principles described in the preceding   section (positions/ranges and characters/lines) are combined,   resulting in four use cases.  The schemes mentioned below refer to   the fragment identifier syntax, described in detail inSection 3.2.2.1.  Character Position   To identify a character position (i.e., a fragment of length zero   between two characters), the 'char' scheme followed by a single   number is used.  This method identifies a position between two   characters (or before the first or after the last character), rather   than identifying a fragment consisting of a number of characters.   Character position counting starts with zero, so the character   position before the first character of a text/plain MIME entity has   the character position zero, and a MIME entity containing n distinct   characters has n+1 distinct character positions, the last one having   the character position n.Wilde & Duerst              Standards Track                     [Page 7]

RFC 5147 text/plain Fragment Identifiers April 20082.2.2. Character Range To identify a fragment of one or more characters (a character range), the 'char' scheme followed by a range specification is used. A character range is a consecutive region of the MIME entity that extends from the starting character position of the range to the ending character position of the range.2.2.3. Line Position To identify a line position (i.e., a fragment of length zero between two lines), the 'line' scheme followed by a single number is used. This method identifies a position between two lines (or before the first or after the last line), rather than identifying a fragment consisting of a number of lines. Line position counting starts with zero, so the line position before the first line of a text/plain MIME entity has the line position zero, and a MIME entity containing n distinct lines has n+1 distinct line positions, the last one having the line position n.2.2.4. Line Range To identify a fragment of one or more lines (a line range), the 'line' scheme followed by a range specification is used. A line range is a consecutive region of the MIME entity that extends from the starting line position of the range to the ending line position of the range.2.3. Fragment Identifier Robustness It is easily possible that a modification of the referenced resource will break a fragment identifier. If applications want to create more robust fragment identifiers, they may do so by adding integrity- check information to fragment identifiers. Such information is used to detect changes in the resource. Applications can then warn users about the possibility that a fragment identifier might have been broken by a modification of the resource. Fragment identifiers are interpreted by clients, and therefore integrity-check information is defined on MIME entities rather than on the resource itself. This means that the integrity-check information is specific to a certain entity. Specifically, content encodings and/or content transfer encodings must be removed before using integrity-check information. Integrity-check information may specify the character encoding that has been used when creating the information, and if such a specification is present, clients MUST check whether the characterWilde & Duerst Standards Track [Page 8]

RFC 5147            text/plain Fragment Identifiers           April 2008   encoding specified and the character encoding of the retrieved MIME   entity are equal, and clients MUST NOT use the integrity check   information if these values differ.  However, clients MAY choose to   transcode the retrieved MIME entity in the case of differing   character encodings, and after doing so, apply integrity checks.   Please note that this method is inherently unreliable because certain   characters or character sequences may have been lost or normalized   due to restrictions in one of the character encodings used.3.  Fragment Identification Syntax   The syntax for the text/plain fragment identifiers is   straightforward.  The syntax defines four schemes, 'char', 'line',   and integrity check (which can either be 'length' or 'md5').  The   'char' and 'line' schemes can be used in two different variants,   either the position variant (with a single number), or the range   variant (with two comma-separated numbers).  An integrity check can   either use the 'length' or the 'md5' scheme to specify a value.   'length' in this case serves as a very weak but easy to calculate   integrity check.   The following syntax definition uses ABNF as defined inRFC 5234 [9],   including the rules DIGIT and HEXDIG.  The mime-charset rule is   defined inRFC 2978 [5].   NOTE:  In the descriptions that follow, specified text values MUST be      used exactly as given, using exactly the indicated lower-case      letters.  In this respect, the ABNF usage differs from [9].   text-fragment   =  text-scheme 0*( ";" integrity-check )   text-scheme     =  ( char-scheme / line-scheme )   char-scheme     =  "char=" ( position / range )   line-scheme     =  "line=" ( position / range )   integrity-check =  ( length-scheme / md5-scheme )                        [ "," mime-charset ]   position        =  number   range           =  ( position "," [ position ] ) / ( "," position )   number          =  1*( DIGIT )   length-scheme   =  "length=" number   md5-scheme      =  "md5=" md5-value   md5-value       =  32HEXDIG3.1.  Integrity Checks   An integrity check can either specify a MIME entity's length, or its   MD5 fingerprint.  In both cases, it can optionally specify the   character encoding that has been used when calculating the integrityWilde & Duerst              Standards Track                     [Page 9]

RFC 5147 text/plain Fragment Identifiers April 2008 check, so that clients interpreting the fragment identifier may check whether they are using the same character encoding for their calculations. For lengths, the character encoding can be necessary because it can influence the character count. As an example, Unicode includes precomposed characters for writing Vietnamese, but in the windows-1258 encoding, also used for writing Vietnamese, some characters have to be encoded with separate diacritics, which means that two characters will be counted. Applying Unicode terminology, this means that the length of a text/plain MIME entity is computed based on its "code points". For MD5 fingerprints, the character encoding is necessary because the MD5 algorithm works on the binary representation of the text/plain resource. To allow future changes to this specification to address developments in cryptography, implementations MUST ignore new types of integrity checks, with names other than 'length' and 'md5'. If several integrity checks are present, an application can use whatever integrity checks it understands, and among these, those integrity checks that provide an appropriate trade-off between performance and the need for integrity checking. Please seeSection 4.3 for further details. The length of a text/plain MIME entity is calculated by using the principles defined inSection 2.1.2. The MD5 fingerprint of a text/ plain MIME entity is calculated by using the algorithm presented in [1], encoding the result in 32 hexadecimal digits (using uppercase or lowercase letters) as a representation of the 128 bits that are the result of the MD5 algorithm. Calculation of integrity checks is done after stripping any potential content-encodings or content-transfer- encodings of the transport mechanism.4. Fragment Identifier Processing Applications implementing support for the mechanism described in this memo MUST behave as described in the following sections.4.1. Handling of Line Endings in text/plain MIME Entities In Internet messages, line endings in text/plain MIME entities are represented by CR+LF character sequences (seeRFC 2046 [3] andRFC3676 [6]). However, some protocols (such as HTTP) additionally allow other conventions for line endings. Also, some operating systems store text/plain entities locally with different line endings (in most cases, Unix uses LF, MacOS traditionally uses CR, and Windows uses CR+LF). Independent of the number of bytes or characters used to represent a line ending, each line ending MUST be counted as one singleWilde & Duerst Standards Track [Page 10]

RFC 5147 text/plain Fragment Identifiers April 2008 character. Implementations interpreting text/plain fragment identifiers MUST take into account the line ending conventions of the protocols and other contexts that they work in. As an example, an implementation working in the context of a Web browser supporting http: URIs has to support the various line ending conventions permitted by HTTP. As another example, an implementation used on local files (e.g., with the file: URI scheme) has to support the conventions used for local storage. All implementations SHOULD support the Internet-wide CR+LF line ending convention, and MAY support additional conventions not related to the protocols or systems they work with. Implementers should be aware of the fact that line endings in plain text entities can be represented by other characters or character sequences than CR+LF. Besides the abovementioned CR and LF, there are also NEL and CR+NEL. In general, the encoding of line endings can also depend on the character encoding of the MIME entity, and implementations have to take this into account where necessary.4.2. Handling of Position Values If any position value (as a position or as part of a range) is greater than the length of the actual MIME entity, then it identifies the last character position or line position of the MIME entity. If the first position value in a range is not present, then the range extends from the start of the MIME entity. If the second position value in a range is not present, then the range extends to the end of the MIME entity. If a range scheme's positions are not properly ordered (i.e., the first number is less than the second), then the fragment identifier MUST be ignored.4.3. Handling of Integrity Checks Clients are not required to implement the handling of integrity checks, so they MAY choose to ignore integrity check information altogether. However, if they do implement integrity checking, the following applies: If a fragment identifier contains one or more integrity checks, and a client retrieves a MIME entity and, using some integrity check(s), detects that the entity has changed (observing the character encoding specification as described inSection 3.1, if present), then the client SHOULD NOT interpret the text/plain fragment identifier. A client MAY signal this situation to the user.Wilde & Duerst Standards Track [Page 11]

RFC 5147 text/plain Fragment Identifiers April 20084.4. Syntax Errors in Fragment Identifiers If a fragment identifier contains a syntax error (i.e., does not conform to the syntax specified inSection 3), then it MUST be ignored by clients. Clients MUST NOT make any attempt to correct or guess fragment identifiers. Syntax errors MAY be reported by clients.5. Examples The following examples show some usages for the fragment identifiers defined in this memo. http://example.com/text.txt#char=100 This URI identifies the position after the 100th character of the text.txt MIME entity. It should be noted that it is not clear which octet(s) of the MIME entity this will be without retrieving the MIME entity and thus knowing which character encoding it is using (in case of HTTP, this information will be given in the Content-Type header of the response). If the MIME entity has fewer than 100 characters, the URI identifies the position after the MIME entity's last character. http://example.com/text.txt#line=10,20 This URI identifies lines 11 to 20 of the text.txt MIME entity. If the MIME entity has fewer than 11 lines, it identifies the position after the last line. If the MIME entity has less than 20 but at least 11 lines, it identifies the range from line 11 to the last line of the MIME entity. https://example.com/text.txt#line=,1 This URI identifies the first line. Please note that the URI scheme has been changed to https. ftp://example.com/text.txt#line=10,20;length=9876,UTF-8 As in the second example, this URI identifies lines 11 to 20 of the text.txt MIME entity. The additional length integrity check specifies that the MIME entity has a length of 9876 characters when encoded in UTF-8. If the client supports the length scheme, it may test the retrieved MIME entity for its length, but only if the retrieved MIME entity uses the UTF-8 encoding or has been locally transcoded into this encoding.Wilde & Duerst Standards Track [Page 12]

RFC 5147 text/plain Fragment Identifiers April 2008 Please note that the FTP protocol, as well as some other protocols underlying some other URI schemes, do not provide explicit information about the media type of the resource being retrieved. Using fragment identifiers with such URI schemes is therefore inherently unreliable. Current user agents use various heuristics to infer some media type for further processing. Processing of the fragment identifier according to this memo is only appropriate if the inferred media type is text/plain.6. IANA Considerations IANA has added a reference to this specification in the text/plain Media Type registration.7. Security Considerations The fact that software implementing fragment identifiers for plain text and software not implementing them differs in behavior, and the fact that different software may show documents or fragments to users in different ways, can lead to misunderstandings on the part of users. Such misunderstandings might be exploited in a way similar to spoofing or phishing. In particular, care has to be taken if fragment identifiers are used together with a mechanism that allows showing only the part of a document identified by a fragment. One scenario may be the use of a fragment identifier to hide small-print legal text. Another scenario may be the inclusion of site-key-like material, which may give the user the impression of using the real site rather than a fake site; other scenarios may also be possible. Possible countermeasures may include but are not limited to displaying the included content within clearly visible boundaries and limiting inclusion to material from the same security realm or from realms that give explicit permission to be included in another realm. Please note that the above issues all apply to the client side; fragment identifiers are not used when resolving a URI to retrieve the representation of a resource, but are only applied on the client side. Implementers and users of fragment identifiers for plain text should also be aware of the security considerations inRFC 3986 [7] andRFC3987 [8].Wilde & Duerst Standards Track [Page 13]

RFC 5147            text/plain Fragment Identifiers           April 20088.  References8.1.  Normative References   [1]   Rivest, R., "The MD5 Message-Digest Algorithm",RFC 1321,         April 1992.   [2]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail         Extensions (MIME) Part One: Format of Internet Message Bodies",RFC 2045, November 1996.   [3]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail         Extensions (MIME) Part Two: Media Types",RFC 2046,         November 1996.   [4]   Bradner, S., "Key words for use in RFCs to Indicate Requirement         Levels",BCP 14,RFC 2119, March 1997.   [5]   Freed, N. and J. Postel, "IANA Charset Registration         Procedures",BCP 19,RFC 2978, October 2000.   [6]   Gellens, R., "The Text/Plain Format and DelSp Parameters",RFC 3676, February 2004.   [7]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform         Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986,         January 2005.   [8]   Duerst, M. and M. Suignard, "Internationalized Resource         Identifiers (IRI)",RFC 3987, January 2005.   [9]   Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax         Specifications: ABNF", STD 68,RFC 5234, January 2008.8.2.  Informative References   [10]  Connolly, D. and L. Masinter, "The 'text/html' Media Type",RFC 2854, June 2000.   [11]  Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 10646",RFC 2781, February 2000.   [12]  Yergeau, F., "UTF-8, a transformation format of ISO 10646",         STD 63,RFC 3629, November 2003.   [13]  ANSI X3.4-1986, "Coded Character Set - 7-Bit American National         Standard Code for Information Interchange", 1986.Wilde & Duerst              Standards Track                    [Page 14]

RFC 5147            text/plain Fragment Identifiers           April 2008   [14]  DeRose, S., Maler, E., and D. Orchard, "XML Linking Language         (XLink) Version 1.0", World Wide Web Consortium Recommendation,         June 2001, <http://www.w3.org/TR/xlink/>.   [15]  Freed, N. and J. Klensin, "Media Type Specifications and         Registration Procedures",BCP 13,RFC 4288, December 2005.Wilde & Duerst              Standards Track                    [Page 15]

RFC 5147            text/plain Fragment Identifiers           April 2008Appendix A.  Acknowledgements   Thanks for comments and suggestions provided by Marcel Baschnagel,   Stephane Bortzmeyer, Tim Bray, Iain Calder, John Cowan, Spencer   Dawkins, Lisa Dusseault, Benja Fallenstein, Ted Hardie, Sam Hartman,   Sandro Hawke, Jeffrey Hutzelman, Cullen Jennings, Graham Klyne, Dan   Kohn, Henrik Levkowetz, Chris Newman, Mark Nottingham, Conrad Parker,   and Tim Polk.Authors' Addresses   Erik Wilde   UC Berkeley   School of Information, 311 South Hall   Berkeley, CA 94720-4600   U.S.A.   Phone: +1-510-6432253   EMail: dret@berkeley.edu   URI:http://dret.net/netdret/   Martin Duerst (Note: Please write "Duerst" with u-umlaut wherever                 possible, for example as "D&#252;rst" in XML and HTML.)   Aoyama Gakuin University   5-10-1 Fuchinobe   Sagamihara, Kanagawa  229-8558   Japan   Phone: +81 42 759 6329   Fax:   +81 42 759 6495   EMail: duerst@it.aoyama.ac.jp   URI:http://www.sw.it.aoyama.ac.jp/D%C3%BCrst/Wilde & Duerst              Standards Track                    [Page 16]

RFC 5147            text/plain Fragment Identifiers           April 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Wilde & Duerst              Standards Track                    [Page 17]

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