RFC3629 日本語訳
3629 UTF-8, a transformation format of ISO 10646. F. Yergeau. November 2003. (Format: TXT=33856 bytes) (Obsoletes RFC2279) (Also STD0063) (Status: STANDARD)
プログラムでの自動翻訳です。
英語原文
Network Working Group F. Yergeau Request for Comments: 3629 Alis Technologies STD: 63 November 2003 Obsoletes: 2279 Category: Standards Track
Network Working Group F. Yergeau Request for Comments: 3629 Alis Technologies STD: 63 November 2003 Obsoletes: 2279 Category: Standards Track
UTF-8, a transformation format of ISO 10646
UTF-8, a transformation format of ISO 10646
Status of this Memo
Status 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.
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.
Copyright Notice
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
Abstract
ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.
ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.
Table of Contents
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Notational conventions . . . . . . . . . . . . . . . . . . . . 3 3. UTF-8 definition . . . . . . . . . . . . . . . . . . . . . . . 4 4. Syntax of UTF-8 Byte Sequences . . . . . . . . . . . . . . . . 5 5. Versions of the standards . . . . . . . . . . . . . . . . . . 6 6. Byte order mark (BOM) . . . . . . . . . . . . . . . . . . . . 6 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. MIME registration . . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 12. Changes from RFC 2279 . . . . . . . . . . . . . . . . . . . . 11 13. Normative References . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Notational conventions . . . . . . . . . . . . . . . . . . . . 3 3. UTF-8 definition . . . . . . . . . . . . . . . . . . . . . . . 4 4. Syntax of UTF-8 Byte Sequences . . . . . . . . . . . . . . . . 5 5. Versions of the standards . . . . . . . . . . . . . . . . . . 6 6. Byte order mark (BOM) . . . . . . . . . . . . . . . . . . . . 6 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. MIME registration . . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 12. Changes from RFC 2279 . . . . . . . . . . . . . . . . . . . . 11 13. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Yergeau Standards Track [Page 1] RFC 3629 UTF-8 November 2003
Yergeau Standards Track [Page 1] RFC 3629 UTF-8 November 2003
14. Informative References . . . . . . . . . . . . . . . . . . . . 12 15. URI's . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 16. Intellectual Property Statement . . . . . . . . . . . . . . . 13 17. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 13 18. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14
14. Informative References . . . . . . . . . . . . . . . . . . . . 12 15. URI's . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 16. Intellectual Property Statement . . . . . . . . . . . . . . . 13 17. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 13 18. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14
1. Introduction
1. Introduction
ISO/IEC 10646 [ISO.10646] defines a large character set called the Universal Character Set (UCS), which encompasses most of the world's writing systems. The same set of characters is defined by the Unicode standard [UNICODE], which further defines additional character properties and other application details of great interest to implementers. Up to the present time, changes in Unicode and amendments and additions to ISO/IEC 10646 have tracked each other, so that the character repertoires and code point assignments have remained in sync. The relevant standardization committees have committed to maintain this very useful synchronism.
ISO/IEC 10646 [ISO.10646] defines a large character set called the Universal Character Set (UCS), which encompasses most of the world's writing systems. The same set of characters is defined by the Unicode standard [UNICODE], which further defines additional character properties and other application details of great interest to implementers. Up to the present time, changes in Unicode and amendments and additions to ISO/IEC 10646 have tracked each other, so that the character repertoires and code point assignments have remained in sync. The relevant standardization committees have committed to maintain this very useful synchronism.
ISO/IEC 10646 and Unicode define several encoding forms of their common repertoire: UTF-8, UCS-2, UTF-16, UCS-4 and UTF-32. In an encoding form, each character is represented as one or more encoding units. All standard UCS encoding forms except UTF-8 have an encoding unit larger than one octet, making them hard to use in many current applications and protocols that assume 8 or even 7 bit characters.
ISO/IEC 10646 and Unicode define several encoding forms of their common repertoire: UTF-8, UCS-2, UTF-16, UCS-4 and UTF-32. In an encoding form, each character is represented as one or more encoding units. All standard UCS encoding forms except UTF-8 have an encoding unit larger than one octet, making them hard to use in many current applications and protocols that assume 8 or even 7 bit characters.
UTF-8, the object of this memo, has a one-octet encoding unit. It uses all bits of an octet, but has the quality of preserving the full US-ASCII [US-ASCII] range: US-ASCII characters are encoded in one octet having the normal US-ASCII value, and any octet with such a value can only stand for a US-ASCII character, and nothing else.
UTF-8, the object of this memo, has a one-octet encoding unit. It uses all bits of an octet, but has the quality of preserving the full US-ASCII [US-ASCII] range: US-ASCII characters are encoded in one octet having the normal US-ASCII value, and any octet with such a value can only stand for a US-ASCII character, and nothing else.
UTF-8 encodes UCS characters as a varying number of octets, where the number of octets, and the value of each, depend on the integer value assigned to the character in ISO/IEC 10646 (the character number, a.k.a. code position, code point or Unicode scalar value). This encoding form has the following characteristics (all values are in hexadecimal):
UTF-8 encodes UCS characters as a varying number of octets, where the number of octets, and the value of each, depend on the integer value assigned to the character in ISO/IEC 10646 (the character number, a.k.a. code position, code point or Unicode scalar value). This encoding form has the following characteristics (all values are in hexadecimal):
o Character numbers from U+0000 to U+007F (US-ASCII repertoire)
correspond to octets 00 to 7F (7 bit US-ASCII values). A direct
consequence is that a plain ASCII string is also a valid UTF-8
string.
o Character numbers from U+0000 to U+007F (US-ASCII repertoire) correspond to octets 00 to 7F (7 bit US-ASCII values). A direct consequence is that a plain ASCII string is also a valid UTF-8 string.
Yergeau Standards Track [Page 2] RFC 3629 UTF-8 November 2003
Yergeau Standards Track [Page 2] RFC 3629 UTF-8 November 2003
o US-ASCII octet values do not appear otherwise in a UTF-8 encoded
character stream. This provides compatibility with file systems
or other software (e.g., the printf() function in C libraries)
that parse based on US-ASCII values but are transparent to other
values.
o US-ASCII octet values do not appear otherwise in a UTF-8 encoded character stream. This provides compatibility with file systems or other software (e.g., the printf() function in C libraries) that parse based on US-ASCII values but are transparent to other values.
o Round-trip conversion is easy between UTF-8 and other encoding
forms.
o Round-trip conversion is easy between UTF-8 and other encoding forms.
o The first octet of a multi-octet sequence indicates the number of
octets in the sequence.
o The first octet of a multi-octet sequence indicates the number of octets in the sequence.
o The octet values C0, C1, F5 to FF never appear.
o The octet values C0, C1, F5 to FF never appear.
o Character boundaries are easily found from anywhere in an octet
stream.
o Character boundaries are easily found from anywhere in an octet stream.
o The byte-value lexicographic sorting order of UTF-8 strings is the
same as if ordered by character numbers. Of course this is of
limited interest since a sort order based on character numbers is
almost never culturally valid.
o The byte-value lexicographic sorting order of UTF-8 strings is the same as if ordered by character numbers. Of course this is of limited interest since a sort order based on character numbers is almost never culturally valid.
o The Boyer-Moore fast search algorithm can be used with UTF-8 data.
o The Boyer-Moore fast search algorithm can be used with UTF-8 data.
o UTF-8 strings can be fairly reliably recognized as such by a
simple algorithm, i.e., the probability that a string of
characters in any other encoding appears as valid UTF-8 is low,
diminishing with increasing string length.
o UTF-8 strings can be fairly reliably recognized as such by a simple algorithm, i.e., the probability that a string of characters in any other encoding appears as valid UTF-8 is low, diminishing with increasing string length.
UTF-8 was devised in September 1992 by Ken Thompson, guided by design criteria specified by Rob Pike, with the objective of defining a UCS transformation format usable in the Plan9 operating system in a non- disruptive manner. Thompson's design was stewarded through standardization by the X/Open Joint Internationalization Group XOJIG (see [FSS_UTF]), bearing the names FSS-UTF (variant FSS/UTF), UTF-2 and finally UTF-8 along the way.
UTF-8 was devised in September 1992 by Ken Thompson, guided by design criteria specified by Rob Pike, with the objective of defining a UCS transformation format usable in the Plan9 operating system in a non- disruptive manner. Thompson's design was stewarded through standardization by the X/Open Joint Internationalization Group XOJIG (see [FSS_UTF]), bearing the names FSS-UTF (variant FSS/UTF), UTF-2 and finally UTF-8 along the way.
2. Notational conventions
2. Notational conventions
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 [RFC2119].
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 [RFC2119].
UCS characters are designated by the U+HHHH notation, where HHHH is a string of from 4 to 6 hexadecimal digits representing the character number in ISO/IEC 10646.
UCS characters are designated by the U+HHHH notation, where HHHH is a string of from 4 to 6 hexadecimal digits representing the character number in ISO/IEC 10646.
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Yergeau Standards Track [Page 3] RFC 3629 UTF-8 November 2003
3. UTF-8 definition
3. UTF-8 definition
UTF-8 is defined by the Unicode Standard [UNICODE]. Descriptions and formulae can also be found in Annex D of ISO/IEC 10646-1 [ISO.10646]
UTF-8 is defined by the Unicode Standard [UNICODE]. Descriptions and formulae can also be found in Annex D of ISO/IEC 10646-1 [ISO.10646]
In UTF-8, characters from the U+0000..U+10FFFF range (the UTF-16 accessible range) are encoded using sequences of 1 to 4 octets. The only octet of a "sequence" of one has the higher-order bit set to 0, the remaining 7 bits being used to encode the character number. In a sequence of n octets, n>1, the initial octet has the n higher-order bits set to 1, followed by a bit set to 0. The remaining bit(s) of that octet contain bits from the number of the character to be encoded. The following octet(s) all have the higher-order bit set to 1 and the following bit set to 0, leaving 6 bits in each to contain bits from the character to be encoded.
In UTF-8, characters from the U+0000..U+10FFFF range (the UTF-16 accessible range) are encoded using sequences of 1 to 4 octets. The only octet of a "sequence" of one has the higher-order bit set to 0, the remaining 7 bits being used to encode the character number. In a sequence of n octets, n>1, the initial octet has the n higher-order bits set to 1, followed by a bit set to 0. The remaining bit(s) of that octet contain bits from the number of the character to be encoded. The following octet(s) all have the higher-order bit set to 1 and the following bit set to 0, leaving 6 bits in each to contain bits from the character to be encoded.
The table below summarizes the format of these different octet types. The letter x indicates bits available for encoding bits of the character number.
The table below summarizes the format of these different octet types. The letter x indicates bits available for encoding bits of the character number.
Char. number range | UTF-8 octet sequence
(hexadecimal) | (binary)
--------------------+---------------------------------------------
0000 0000-0000 007F | 0xxxxxxx
0000 0080-0000 07FF | 110xxxxx 10xxxxxx
0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
Char. number range | UTF-8 octet sequence (hexadecimal) | (binary) --------------------+--------------------------------------------- 0000 0000-0000 007F | 0xxxxxxx 0000 0080-0000 07FF | 110xxxxx 10xxxxxx 0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx 0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
Encoding a character to UTF-8 proceeds as follows:
Encoding a character to UTF-8 proceeds as follows:
1. Determine the number of octets required from the character number
and the first column of the table above. It is important to note
that the rows of the table are mutually exclusive, i.e., there is
only one valid way to encode a given character.
1. Determine the number of octets required from the character number and the first column of the table above. It is important to note that the rows of the table are mutually exclusive, i.e., there is only one valid way to encode a given character.
2. Prepare the high-order bits of the octets as per the second
column of the table.
2. Prepare the high-order bits of the octets as per the second column of the table.
3. Fill in the bits marked x from the bits of the character number,
expressed in binary. Start by putting the lowest-order bit of
the character number in the lowest-order position of the last
octet of the sequence, then put the next higher-order bit of the
character number in the next higher-order position of that octet,
etc. When the x bits of the last octet are filled in, move on to
the next to last octet, then to the preceding one, etc. until all
x bits are filled in.
3. Fill in the bits marked x from the bits of the character number, expressed in binary. Start by putting the lowest-order bit of the character number in the lowest-order position of the last octet of the sequence, then put the next higher-order bit of the character number in the next higher-order position of that octet, etc. When the x bits of the last octet are filled in, move on to the next to last octet, then to the preceding one, etc. until all x bits are filled in.
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Yergeau Standards Track [Page 4] RFC 3629 UTF-8 November 2003
The definition of UTF-8 prohibits encoding character numbers between U+D800 and U+DFFF, which are reserved for use with the UTF-16 encoding form (as surrogate pairs) and do not directly represent characters. When encoding in UTF-8 from UTF-16 data, it is necessary to first decode the UTF-16 data to obtain character numbers, which are then encoded in UTF-8 as described above. This contrasts with CESU-8 [CESU-8], which is a UTF-8-like encoding that is not meant for use on the Internet. CESU-8 operates similarly to UTF-8 but encodes the UTF-16 code values (16-bit quantities) instead of the character number (code point). This leads to different results for character numbers above 0xFFFF; the CESU-8 encoding of those characters is NOT valid UTF-8.
The definition of UTF-8 prohibits encoding character numbers between U+D800 and U+DFFF, which are reserved for use with the UTF-16 encoding form (as surrogate pairs) and do not directly represent characters. When encoding in UTF-8 from UTF-16 data, it is necessary to first decode the UTF-16 data to obtain character numbers, which are then encoded in UTF-8 as described above. This contrasts with CESU-8 [CESU-8], which is a UTF-8-like encoding that is not meant for use on the Internet. CESU-8 operates similarly to UTF-8 but encodes the UTF-16 code values (16-bit quantities) instead of the character number (code point). This leads to different results for character numbers above 0xFFFF; the CESU-8 encoding of those characters is NOT valid UTF-8.
Decoding a UTF-8 character proceeds as follows:
Decoding a UTF-8 character proceeds as follows:
1. Initialize a binary number with all bits set to 0. Up to 21 bits
may be needed.
1. Initialize a binary number with all bits set to 0. Up to 21 bits may be needed.
2. Determine which bits encode the character number from the number
of octets in the sequence and the second column of the table
above (the bits marked x).
2. Determine which bits encode the character number from the number of octets in the sequence and the second column of the table above (the bits marked x).
3. Distribute the bits from the sequence to the binary number, first
the lower-order bits from the last octet of the sequence and
proceeding to the left until no x bits are left. The binary
number is now equal to the character number.
3. Distribute the bits from the sequence to the binary number, first the lower-order bits from the last octet of the sequence and proceeding to the left until no x bits are left. The binary number is now equal to the character number.
Implementations of the decoding algorithm above MUST protect against decoding invalid sequences. For instance, a naive implementation may decode the overlong UTF-8 sequence C0 80 into the character U+0000, or the surrogate pair ED A1 8C ED BE B4 into U+233B4. Decoding invalid sequences may have security consequences or cause other problems. See Security Considerations (Section 10) below.
Implementations of the decoding algorithm above MUST protect against decoding invalid sequences. For instance, a naive implementation may decode the overlong UTF-8 sequence C0 80 into the character U+0000, or the surrogate pair ED A1 8C ED BE B4 into U+233B4. Decoding invalid sequences may have security consequences or cause other problems. See Security Considerations (Section 10) below.
4. Syntax of UTF-8 Byte Sequences
4. Syntax of UTF-8 Byte Sequences
For the convenience of implementors using ABNF, a definition of UTF-8 in ABNF syntax is given here.
For the convenience of implementors using ABNF, a definition of UTF-8 in ABNF syntax is given here.
A UTF-8 string is a sequence of octets representing a sequence of UCS characters. An octet sequence is valid UTF-8 only if it matches the following syntax, which is derived from the rules for encoding UTF-8 and is expressed in the ABNF of [RFC2234].
A UTF-8 string is a sequence of octets representing a sequence of UCS characters. An octet sequence is valid UTF-8 only if it matches the following syntax, which is derived from the rules for encoding UTF-8 and is expressed in the ABNF of [RFC2234].
UTF8-octets = *( UTF8-char ) UTF8-char = UTF8-1 / UTF8-2 / UTF8-3 / UTF8-4 UTF8-1 = %x00-7F UTF8-2 = %xC2-DF UTF8-tail
UTF8-octets = *( UTF8-char ) UTF8-char = UTF8-1 / UTF8-2 / UTF8-3 / UTF8-4 UTF8-1 = %x00-7F UTF8-2 = %xC2-DF UTF8-tail
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Yergeau Standards Track [Page 5] RFC 3629 UTF-8 November 2003
UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) /
%xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail )
UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) /
%xF4 %x80-8F 2( UTF8-tail )
UTF8-tail = %x80-BF
UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) / %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail ) UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) / %xF4 %x80-8F 2( UTF8-tail ) UTF8-tail = %x80-BF
NOTE -- The authoritative definition of UTF-8 is in [UNICODE]. This grammar is believed to describe the same thing Unicode describes, but does not claim to be authoritative. Implementors are urged to rely on the authoritative source, rather than on this ABNF.
NOTE -- The authoritative definition of UTF-8 is in [UNICODE]. This grammar is believed to describe the same thing Unicode describes, but does not claim to be authoritative. Implementors are urged to rely on the authoritative source, rather than on this ABNF.
5. Versions of the standards
5. Versions of the standards
ISO/IEC 10646 is updated from time to time by publication of amendments and additional parts; similarly, new versions of the Unicode standard are published over time. Each new version obsoletes and replaces the previous one, but implementations, and more significantly data, are not updated instantly.
ISO/IEC 10646 is updated from time to time by publication of amendments and additional parts; similarly, new versions of the Unicode standard are published over time. Each new version obsoletes and replaces the previous one, but implementations, and more significantly data, are not updated instantly.
In general, the changes amount to adding new characters, which does not pose particular problems with old data. In 1996, Amendment 5 to the 1993 edition of ISO/IEC 10646 and Unicode 2.0 moved and expanded the Korean Hangul block, thereby making any previous data containing Hangul characters invalid under the new version. Unicode 2.0 has the same difference from Unicode 1.1. The justification for allowing such an incompatible change was that there were no major implementations and no significant amounts of data containing Hangul. The incident has been dubbed the "Korean mess", and the relevant committees have pledged to never, ever again make such an incompatible change (see Unicode Consortium Policies [1]).
In general, the changes amount to adding new characters, which does not pose particular problems with old data. In 1996, Amendment 5 to the 1993 edition of ISO/IEC 10646 and Unicode 2.0 moved and expanded the Korean Hangul block, thereby making any previous data containing Hangul characters invalid under the new version. Unicode 2.0 has the same difference from Unicode 1.1. The justification for allowing such an incompatible change was that there were no major implementations and no significant amounts of data containing Hangul. The incident has been dubbed the "Korean mess", and the relevant committees have pledged to never, ever again make such an incompatible change (see Unicode Consortium Policies [1]).
New versions, and in particular any incompatible changes, have consequences regarding MIME charset labels, to be discussed in MIME registration (Section 8).
New versions, and in particular any incompatible changes, have consequences regarding MIME charset labels, to be discussed in MIME registration (Section 8).
6. Byte order mark (BOM)
6. Byte order mark (BOM)
The UCS character U+FEFF "ZERO WIDTH NO-BREAK SPACE" is also known informally as "BYTE ORDER MARK" (abbreviated "BOM"). This character can be used as a genuine "ZERO WIDTH NO-BREAK SPACE" within text, but the BOM name hints at a second possible usage of the character: to prepend a U+FEFF character to a stream of UCS characters as a "signature". A receiver of such a serialized stream may then use the initial character as a hint that the stream consists of UCS characters and also to recognize which UCS encoding is involved and, with encodings having a multi-octet encoding unit, as a way to
The UCS character U+FEFF "ZERO WIDTH NO-BREAK SPACE" is also known informally as "BYTE ORDER MARK" (abbreviated "BOM"). This character can be used as a genuine "ZERO WIDTH NO-BREAK SPACE" within text, but the BOM name hints at a second possible usage of the character: to prepend a U+FEFF character to a stream of UCS characters as a "signature". A receiver of such a serialized stream may then use the initial character as a hint that the stream consists of UCS characters and also to recognize which UCS encoding is involved and, with encodings having a multi-octet encoding unit, as a way to
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Yergeau Standards Track [Page 6] RFC 3629 UTF-8 November 2003
recognize the serialization order of the octets. UTF-8 having a single-octet encoding unit, this last function is useless and the BOM will always appear as the octet sequence EF BB BF.
recognize the serialization order of the octets. UTF-8 having a single-octet encoding unit, this last function is useless and the BOM will always appear as the octet sequence EF BB BF.
It is important to understand that the character U+FEFF appearing at any position other than the beginning of a stream MUST be interpreted with the semantics for the zero-width non-breaking space, and MUST NOT be interpreted as a signature. When interpreted as a signature, the Unicode standard suggests than an initial U+FEFF character may be stripped before processing the text. Such stripping is necessary in some cases (e.g., when concatenating two strings, because otherwise the resulting string may contain an unintended "ZERO WIDTH NO-BREAK SPACE" at the connection point), but might affect an external process at a different layer (such as a digital signature or a count of the characters) that is relying on the presence of all characters in the stream. It is therefore RECOMMENDED to avoid stripping an initial U+FEFF interpreted as a signature without a good reason, to ignore it instead of stripping it when appropriate (such as for display) and to strip it only when really necessary.
It is important to understand that the character U+FEFF appearing at any position other than the beginning of a stream MUST be interpreted with the semantics for the zero-width non-breaking space, and MUST NOT be interpreted as a signature. When interpreted as a signature, the Unicode standard suggests than an initial U+FEFF character may be stripped before processing the text. Such stripping is necessary in some cases (e.g., when concatenating two strings, because otherwise the resulting string may contain an unintended "ZERO WIDTH NO-BREAK SPACE" at the connection point), but might affect an external process at a different layer (such as a digital signature or a count of the characters) that is relying on the presence of all characters in the stream. It is therefore RECOMMENDED to avoid stripping an initial U+FEFF interpreted as a signature without a good reason, to ignore it instead of stripping it when appropriate (such as for display) and to strip it only when really necessary.
U+FEFF in the first position of a stream MAY be interpreted as a zero-width non-breaking space, and is not always a signature. In an attempt at diminishing this uncertainty, Unicode 3.2 adds a new character, U+2060 "WORD JOINER", with exactly the same semantics and usage as U+FEFF except for the signature function, and strongly recommends its exclusive use for expressing word-joining semantics. Eventually, following this recommendation will make it all but certain that any initial U+FEFF is a signature, not an intended "ZERO WIDTH NO-BREAK SPACE".
U+FEFF in the first position of a stream MAY be interpreted as a zero-width non-breaking space, and is not always a signature. In an attempt at diminishing this uncertainty, Unicode 3.2 adds a new character, U+2060 "WORD JOINER", with exactly the same semantics and usage as U+FEFF except for the signature function, and strongly recommends its exclusive use for expressing word-joining semantics. Eventually, following this recommendation will make it all but certain that any initial U+FEFF is a signature, not an intended "ZERO WIDTH NO-BREAK SPACE".
In the meantime, the uncertainty unfortunately remains and may affect Internet protocols. Protocol specifications MAY restrict usage of U+FEFF as a signature in order to reduce or eliminate the potential ill effects of this uncertainty. In the interest of striking a balance between the advantages (reduction of uncertainty) and drawbacks (loss of the signature function) of such restrictions, it is useful to distinguish a few cases:
In the meantime, the uncertainty unfortunately remains and may affect Internet protocols. Protocol specifications MAY restrict usage of U+FEFF as a signature in order to reduce or eliminate the potential ill effects of this uncertainty. In the interest of striking a balance between the advantages (reduction of uncertainty) and drawbacks (loss of the signature function) of such restrictions, it is useful to distinguish a few cases:
o A protocol SHOULD forbid use of U+FEFF as a signature for those
textual protocol elements that the protocol mandates to be always
UTF-8, the signature function being totally useless in those
cases.
o A protocol SHOULD forbid use of U+FEFF as a signature for those textual protocol elements that the protocol mandates to be always UTF-8, the signature function being totally useless in those cases.
o A protocol SHOULD also forbid use of U+FEFF as a signature for
those textual protocol elements for which the protocol provides
character encoding identification mechanisms, when it is expected
that implementations of the protocol will be in a position to
always use the mechanisms properly. This will be the case when
o A protocol SHOULD also forbid use of U+FEFF as a signature for those textual protocol elements for which the protocol provides character encoding identification mechanisms, when it is expected that implementations of the protocol will be in a position to always use the mechanisms properly. This will be the case when
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the protocol elements are maintained tightly under the control of
the implementation from the time of their creation to the time of
their (properly labeled) transmission.
the protocol elements are maintained tightly under the control of the implementation from the time of their creation to the time of their (properly labeled) transmission.
o A protocol SHOULD NOT forbid use of U+FEFF as a signature for
those textual protocol elements for which the protocol does not
provide character encoding identification mechanisms, when a ban
would be unenforceable, or when it is expected that
implementations of the protocol will not be in a position to
always use the mechanisms properly. The latter two cases are
likely to occur with larger protocol elements such as MIME
entities, especially when implementations of the protocol will
obtain such entities from file systems, from protocols that do not
have encoding identification mechanisms for payloads (such as FTP)
or from other protocols that do not guarantee proper
identification of character encoding (such as HTTP).
o A protocol SHOULD NOT forbid use of U+FEFF as a signature for those textual protocol elements for which the protocol does not provide character encoding identification mechanisms, when a ban would be unenforceable, or when it is expected that implementations of the protocol will not be in a position to always use the mechanisms properly. The latter two cases are likely to occur with larger protocol elements such as MIME entities, especially when implementations of the protocol will obtain such entities from file systems, from protocols that do not have encoding identification mechanisms for payloads (such as FTP) or from other protocols that do not guarantee proper identification of character encoding (such as HTTP).
When a protocol forbids use of U+FEFF as a signature for a certain protocol element, then any initial U+FEFF in that protocol element MUST be interpreted as a "ZERO WIDTH NO-BREAK SPACE". When a protocol does NOT forbid use of U+FEFF as a signature for a certain protocol element, then implementations SHOULD be prepared to handle a signature in that element and react appropriately: using the signature to identify the character encoding as necessary and stripping or ignoring the signature as appropriate.
When a protocol forbids use of U+FEFF as a signature for a certain protocol element, then any initial U+FEFF in that protocol element MUST be interpreted as a "ZERO WIDTH NO-BREAK SPACE". When a protocol does NOT forbid use of U+FEFF as a signature for a certain protocol element, then implementations SHOULD be prepared to handle a signature in that element and react appropriately: using the signature to identify the character encoding as necessary and stripping or ignoring the signature as appropriate.
7. Examples
7. Examples
The character sequence U+0041 U+2262 U+0391 U+002E "A<NOT IDENTICAL TO><ALPHA>." is encoded in UTF-8 as follows:
The character sequence U+0041 U+2262 U+0391 U+002E "A<NOT IDENTICAL TO><ALPHA>." is encoded in UTF-8 as follows:
--+--------+-----+--
41 E2 89 A2 CE 91 2E
--+--------+-----+--
--+--------+-----+-- 41 E2 89 A2 CE 91 2E --+--------+-----+--
The character sequence U+D55C U+AD6D U+C5B4 (Korean "hangugeo", meaning "the Korean language") is encoded in UTF-8 as follows:
The character sequence U+D55C U+AD6D U+C5B4 (Korean "hangugeo", meaning "the Korean language") is encoded in UTF-8 as follows:
--------+--------+--------
ED 95 9C EA B5 AD EC 96 B4
--------+--------+--------
--------+--------+-------- ED 95 9C EA B5 AD EC 96 B4 --------+--------+--------
The character sequence U+65E5 U+672C U+8A9E (Japanese "nihongo", meaning "the Japanese language") is encoded in UTF-8 as follows:
The character sequence U+65E5 U+672C U+8A9E (Japanese "nihongo", meaning "the Japanese language") is encoded in UTF-8 as follows:
--------+--------+--------
E6 97 A5 E6 9C AC E8 AA 9E
--------+--------+--------
--------+--------+-------- E6 97 A5 E6 9C AC E8 AA 9E --------+--------+--------
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The character U+233B4 (a Chinese character meaning 'stump of tree'), prepended with a UTF-8 BOM, is encoded in UTF-8 as follows:
The character U+233B4 (a Chinese character meaning 'stump of tree'), prepended with a UTF-8 BOM, is encoded in UTF-8 as follows:
--------+-----------
EF BB BF F0 A3 8E B4
--------+-----------
--------+----------- EF BB BF F0 A3 8E B4 --------+-----------
8. MIME registration
8. MIME registration
This memo serves as the basis for registration of the MIME charset parameter for UTF-8, according to [RFC2978]. The charset parameter value is "UTF-8". This string labels media types containing text consisting of characters from the repertoire of ISO/IEC 10646 including all amendments at least up to amendment 5 of the 1993 edition (Korean block), encoded to a sequence of octets using the encoding scheme outlined above. UTF-8 is suitable for use in MIME content types under the "text" top-level type.
This memo serves as the basis for registration of the MIME charset parameter for UTF-8, according to [RFC2978]. The charset parameter value is "UTF-8". This string labels media types containing text consisting of characters from the repertoire of ISO/IEC 10646 including all amendments at least up to amendment 5 of the 1993 edition (Korean block), encoded to a sequence of octets using the encoding scheme outlined above. UTF-8 is suitable for use in MIME content types under the "text" top-level type.
It is noteworthy that the label "UTF-8" does not contain a version identification, referring generically to ISO/IEC 10646. This is intentional, the rationale being as follows:
It is noteworthy that the label "UTF-8" does not contain a version identification, referring generically to ISO/IEC 10646. This is intentional, the rationale being as follows:
A MIME charset label is designed to give just the information needed to interpret a sequence of bytes received on the wire into a sequence of characters, nothing more (see [RFC2045], section 2.2). As long as a character set standard does not change incompatibly, version numbers serve no purpose, because one gains nothing by learning from the tag that newly assigned characters may be received that one doesn't know about. The tag itself doesn't teach anything about the new characters, which are going to be received anyway.
A MIME charset label is designed to give just the information needed to interpret a sequence of bytes received on the wire into a sequence of characters, nothing more (see [RFC2045], section 2.2). As long as a character set standard does not change incompatibly, version numbers serve no purpose, because one gains nothing by learning from the tag that newly assigned characters may be received that one doesn't know about. The tag itself doesn't teach anything about the new characters, which are going to be received anyway.
Hence, as long as the standards evolve compatibly, the apparent advantage of having labels that identify the versions is only that, apparent. But there is a disadvantage to such version-dependent labels: when an older application receives data accompanied by a newer, unknown label, it may fail to recognize the label and be completely unable to deal with the data, whereas a generic, known label would have triggered mostly correct processing of the data, which may well not contain any new characters.
Hence, as long as the standards evolve compatibly, the apparent advantage of having labels that identify the versions is only that, apparent. But there is a disadvantage to such version-dependent labels: when an older application receives data accompanied by a newer, unknown label, it may fail to recognize the label and be completely unable to deal with the data, whereas a generic, known label would have triggered mostly correct processing of the data, which may well not contain any new characters.
Now the "Korean mess" (ISO/IEC 10646 amendment 5) is an incompatible change, in principle contradicting the appropriateness of a version independent MIME charset label as described above. But the compatibility problem can only appear with data containing Korean Hangul characters encoded according to Unicode 1.1 (or equivalently ISO/IEC 10646 before amendment 5), and there is arguably no such data to worry about, this being the very reason the incompatible change was deemed acceptable.
Now the "Korean mess" (ISO/IEC 10646 amendment 5) is an incompatible change, in principle contradicting the appropriateness of a version independent MIME charset label as described above. But the compatibility problem can only appear with data containing Korean Hangul characters encoded according to Unicode 1.1 (or equivalently ISO/IEC 10646 before amendment 5), and there is arguably no such data to worry about, this being the very reason the incompatible change was deemed acceptable.
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In practice, then, a version-independent label is warranted, provided the label is understood to refer to all versions after Amendment 5, and provided no incompatible change actually occurs. Should incompatible changes occur in a later version of ISO/IEC 10646, the MIME charset label defined here will stay aligned with the previous version until and unless the IETF specifically decides otherwise.
In practice, then, a version-independent label is warranted, provided the label is understood to refer to all versions after Amendment 5, and provided no incompatible change actually occurs. Should incompatible changes occur in a later version of ISO/IEC 10646, the MIME charset label defined here will stay aligned with the previous version until and unless the IETF specifically decides otherwise.
9. IANA Considerations
9. IANA Considerations
The entry for UTF-8 in the IANA charset registry has been updated to point to this memo.
The entry for UTF-8 in the IANA charset registry has been updated to point to this memo.
10. Security Considerations
10. Security Considerations
Implementers of UTF-8 need to consider the security aspects of how they handle illegal UTF-8 sequences. It is conceivable that in some circumstances an attacker would be able to exploit an incautious UTF-8 parser by sending it an octet sequence that is not permitted by the UTF-8 syntax.
Implementers of UTF-8 need to consider the security aspects of how they handle illegal UTF-8 sequences. It is conceivable that in some circumstances an attacker would be able to exploit an incautious UTF-8 parser by sending it an octet sequence that is not permitted by the UTF-8 syntax.
A particularly subtle form of this attack can be carried out against
a parser which performs security-critical validity checks against the
UTF-8 encoded form of its input, but interprets certain illegal octet
sequences as characters. For example, a parser might prohibit the
NUL character when encoded as the single-octet sequence 00, but
erroneously allow the illegal two-octet sequence C0 80 and interpret
it as a NUL character. Another example might be a parser which
prohibits the octet sequence 2F 2E 2E 2F ("/../"), yet permits the
illegal octet sequence 2F C0 AE 2E 2F. This last exploit has
actually been used in a widespread virus attacking Web servers in
2001; thus, the security threat is very real.
A particularly subtle form of this attack can be carried out against a parser which performs security-critical validity checks against the UTF-8 encoded form of its input, but interprets certain illegal octet sequences as characters. For example, a parser might prohibit the NUL character when encoded as the single-octet sequence 00, but erroneously allow the illegal two-octet sequence C0 80 and interpret it as a NUL character. Another example might be a parser which prohibits the octet sequence 2F 2E 2E 2F ("/../"), yet permits the illegal octet sequence 2F C0 AE 2E 2F. This last exploit has actually been used in a widespread virus attacking Web servers in 2001; thus, the security threat is very real.
Another security issue occurs when encoding to UTF-8: the ISO/IEC 10646 description of UTF-8 allows encoding character numbers up to U+7FFFFFFF, yielding sequences of up to 6 bytes. There is therefore a risk of buffer overflow if the range of character numbers is not explicitly limited to U+10FFFF or if buffer sizing doesn't take into account the possibility of 5- and 6-byte sequences.
以下をUTF-8にコード化するとき、別の安全保障問題は起こります。 UTF-8のISO/IECの10646記述で、最大6バイトの系列をもたらして、U+7FFFFFFFまでのキャラクタ番号をコード化します。 したがって、キャラクタ番号の範囲が明らかにU+10FFFFに制限されないか、またはバッファサイズ処理が5と6バイトの系列の可能性を考慮に入れないなら、バッファオーバーフローのリスクがあります。
Security may also be impacted by a characteristic of several character encodings, including UTF-8: the "same thing" (as far as a user can tell) can be represented by several distinct character sequences. For instance, an e with acute accent can be represented by the precomposed U+00E9 E ACUTE character or by the canonically equivalent sequence U+0065 U+0301 (E + COMBINING ACUTE). Even though UTF-8 provides a single byte sequence for each character sequence, the existence of multiple character sequences for "the same thing" may have security consequences whenever string matching, indexing,
また、UTF-8を含む数個のキャラクタencodingsの特性でセキュリティに影響を与えるかもしれません: いくつかの異なったキャラクタシーケンスは「同じもの」(ユーザが判断できる限り)を表すことができます。 例えば、precomposed U+00E9E ACUTEキャラクタか正準な同等な系列U+0065U+0301(E+COMBINING ACUTE)で鋭アクセントがあるeを表すことができます。 UTF-8はただ一つのバイト列を各キャラクタシーケンスに提供しますが、「同じもの」のための複数のキャラクタシーケンスの存在に、ストリングマッチングであって、索引をつけるときはいつも、セキュリティ結果があるかもしれません。
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searching, sorting, regular expression matching and selection are involved. An example would be string matching of an identifier appearing in a credential and in access control list entries. This issue is amenable to solutions based on Unicode Normalization Forms, see [UAX15].
探すこと、ソーティング、正規表現マッチング、および選択はかかわります。 例は信任状とアクセスコントロールリストエントリーに載っている識別子のストリングマッチングでしょう。 [UAX15]は、この問題がユニコードNormalization Formsに基づく解決策に従順であることを見ます。
11. Acknowledgements
11. 承認
The following have participated in the drafting and discussion of this memo: James E. Agenbroad, Harald Alvestrand, Andries Brouwer, Mark Davis, Martin J. Duerst, Patrick Faltstrom, Ned Freed, David Goldsmith, Tony Hansen, Edwin F. Hart, Paul Hoffman, David Hopwood, Simon Josefsson, Kent Karlsson, Dan Kohn, Markus Kuhn, Michael Kung, Alain LaBonte, Ira McDonald, Alexey Melnikov, MURATA Makoto, John Gardiner Myers, Chris Newman, Dan Oscarsson, Roozbeh Pournader, Murray Sargent, Markus Scherer, Keld Simonsen, Arnold Winkler, Kenneth Whistler and Misha Wolf.
以下はこのメモの草稿と議論に参加しました: サイモンJosefsson、ケントのジェームスE.Agenbroad、ハラルドAlvestrand、Andriesブルーエル、マーク・デイビス、マーチンJ.Duerst、パトリックFaltstrom、解放されたネッド、デヴィッド・ゴールドスミス、トニー・ハンセン、エドウィン・F.ハート、ポール・ホフマン、デヴィッドHopwood、カールソン、ダン・コーン、マーカス・キューン、マイケル・キュング、アランLaBonte、イラ・マクドナルド、Alexeyメリニコフ、誠ムラタ、ジョン・ガーディナー・マイアーズ、クリス・ニューマン、ダン・オスカルソン、Roozbeh Pournader、マレーサージェント、マーカス・シェーラー、Keldシモンセン、アーノルド・ウィンクラー、ケネスウィスラー、およびミーシャ・ヴォルフ。
12. Changes from RFC 2279
12. RFC2279からの変化
o Restricted the range of characters to 0000-10FFFF (the UTF-16
accessible range).
o 0000-10 FFFF(UTF-16のアクセスしやすい範囲)へのキャラクタの範囲を制限しました。
o Made Unicode the source of the normative definition of UTF-8,
keeping ISO/IEC 10646 as the reference for characters.
o キャラクタの参照としてISO/IEC10646を維持して、ユニコードをUTF-8の標準の定義の源にしました。
o Straightened out terminology. UTF-8 now described in terms of an
encoding form of the character number. UCS-2 and UCS-4 almost
disappeared.
o 用語をまっすぐにしました。 現在キャラクタ番号のコード化フォームで説明されているUTF-8。 UCS-2とUCS-4はもう少しで見えなくなるところでした。
o Turned the note warning against decoding of invalid sequences into
a normative MUST NOT.
o aへの標準の無効の系列を解読することに対する警告がターンしてはいけない音をターンしました。
o Added a new section about the UTF-8 BOM, with advice for
protocols.
o プロトコルのためのアドバイスでUTF-8 BOMに関する新しいセクションを加えました。
o Removed suggested UNICODE-1-1-UTF-8 MIME charset registration.
o 提案されたユニコード1-1UTF-8 MIME charset登録を取り除きました。
o Added an ABNF syntax for valid UTF-8 octet sequences
o 有効なUTF-8八重奏系列のためにABNF構文を加えます。
o Expanded Security Considerations section, in particular impact of
Unicode normalization
o ユニコード正常化の特定の影響での拡張Security Considerations部
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13. Normative References
13. 引用規格
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119] ブラドナー、S.、「Indicate Requirement LevelsへのRFCsにおける使用のためのキーワード」、BCP14、RFC2119、1997年3月。
[ISO.10646] International Organization for Standardization,
"Information Technology - Universal Multiple-octet coded
Character Set (UCS)", ISO/IEC Standard 10646, comprised
of ISO/IEC 10646-1:2000, "Information technology --
Universal Multiple-Octet Coded Character Set (UCS) --
Part 1: Architecture and Basic Multilingual Plane",
ISO/IEC 10646-2:2001, "Information technology --
Universal Multiple-Octet Coded Character Set (UCS) --
Part 2: Supplementary Planes" and ISO/IEC 10646-
1:2000/Amd 1:2002, "Mathematical symbols and other
characters".
[ISO.10646]国際標準化機構、「情報Technology--普遍的なMultiple-八重奏は文字コード(UCS)をコード化しました」、ISO/IEC10646-1:2000から成るISO/IEC Standard10646、「情報技術--普遍的なMultiple-八重奏Coded文字コード(UCS)--第1部:、」 「構造と基本多言語水準」、ISO/IEC10646-2:2001、「情報技術--普遍的なMultiple-八重奏Coded文字コード(UCS)--第2部:、」 「補っているプラネス」とISO/IEC10646- 1: 2000/Amd1:2002と、「数学記号と他のキャラクタ。」
[UNICODE] The Unicode Consortium, "The Unicode Standard -- Version
4.0", defined by The Unicode Standard, Version 4.0
(Boston, MA, Addison-Wesley, 2003. ISBN 0-321-18578-1),
April 2003, <http://www.unicode.org/unicode/standard/
versions/enumeratedversions.html#Unicode_4_0_0>.
[ユニコード] ユニコードConsortium、「ユニコード規格、バージョン4.0(ボストン(MA)アディソン-ウエスリー、2003ISBN0-321-18578-1)、2003年4月、<http://www.unicode.org/ユニコード/規格/バージョン/enumeratedversions.html#ユニコード_4_0_0>によってバージョン4インチであって、定義されたユニコード規格。」
14. Informative References
14. 有益な参照
[CESU-8] Phipps, T., "Unicode Technical Report #26: Compatibility
Encoding Scheme for UTF-16: 8-Bit (CESU-8)", UTR 26,
April 2002,
<http://www.unicode.org/unicode/reports/tr26/>.
[CESU-8]フィップス、T.、「ユニコード技術報告書#26:」 UTF-16の互換性コード化計画: 「8ビットの(CESU-8)」、UTR26、2002年4月、<http://www.unicode.org/unicode/reports/tr26/>。
[FSS_UTF] X/Open Company Ltd., "X/Open Preliminary Specification --
File System Safe UCS Transformation Format (FSS-UTF)",
May 1993, <http://wwwold.dkuug.dk/jtc1/sc22/wg20/docs/
N193-FSS-UTF.pdf>.
「X/Openの予備の仕様--システムの安全なUCS変化形式(FSS-UTF)をファイルする」という[FSS_UTF]X/Open会社株式会社は1993、<http://wwwold.dkuug.dk/jtc1/sc22/wg20/docs/N193-FSS-UTF.pdf>がそうするかもしれません。
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
解放された[RFC2045]、N.、およびN.Borenstein、「マルチパーパスインターネットメールエクステンション(MIME)は1つを分けます」。 「インターネットメッセージ本体の形式」、RFC2045、1996年11月。
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2234] クロッカー、D.、およびP.Overell、「構文仕様のための増大しているBNF:」 "ABNF"、1997年11月のRFC2234。
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000.
解放された[RFC2978]とN.とJ.ポステル、「IANA Charset登録手順」、BCP19、RFC2978、2000年10月。
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[UAX15] Davis, M. and M. Duerst, "Unicode Standard Annex #15:
Unicode Normalization Forms", An integral part of The
Unicode Standard, Version 4.0.0, April 2003, <http://
www.unicode.org/unicode/reports/tr15>.
[UAX15] デイヴィス、M.、およびM.Duerst、「ユニコード規格は#15、を付加します」。 「ユニコードNormalization Forms」、ユニコードStandardのAnの不可欠の部分、バージョン、4.0、.0、2003年4月<httpな://www.unicode.org/ユニコード/レポート/tr15>。
[US-ASCII] American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
[米国-ASCII] American National Standards Institut、「7コード化文字集合--ビット、情報交換用米国標準コード、」、ANSI X3.4、1986
15. URIs
15. URI
[1] <http://www.unicode.org/unicode/standard/policies.html>
[1] <http://www.unicode.org/ユニコード/規格/policies.html>。
16. Intellectual Property Statement
16. 知的所有権声明
The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat.
IETFはどんな知的所有権の正当性か範囲、実現に関係すると主張されるかもしれない他の権利、本書では説明された技術の使用またはそのような権利の下におけるどんなライセンスも利用可能であるかもしれない、または利用可能でないかもしれない範囲に関しても立場を全く取りません。 どちらも、それはそれを表しません。いずれもどんなそのような権利も特定するための努力にしました。 BCP-11で標準化過程の権利と規格関連のドキュメンテーションに関するIETFの手順に関する情報を見つけることができます。 権利のクレームのコピーで利用可能に作られるべきライセンスの保証、または一般的なライセンスか許可が作成者によるそのような所有権の使用に得させられた試みの結果が公表といずれにも利用可能になったか、またはIETF事務局からこの仕様のユーザを得ることができます。
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director.
IETFはこの規格を練習するのに必要であるかもしれない技術をカバーするかもしれないどんな著作権もその注目していただくどんな利害関係者、特許、特許出願、または他の所有権も招待します。 IETF専務に情報を記述してください。
17. Author's Address
17. 作者のアドレス
Francois Yergeau Alis Technologies 100, boul. Alexis-Nihon, bureau 600 Montreal, QC H4M 2P2 Canada
フランソアYergeau Alis Technologies100、boul。 アレックサス-日本、局600のモントリオール、QC H4M 2P2カナダ
Phone: +1 514 747 2547 Fax: +1 514 747 2561 EMail: fyergeau@alis.com
以下に電話をしてください。 +1 514 747、2547Fax: +1 2561年の514 747メール: fyergeau@alis.com
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18. Full Copyright Statement
18. 完全な著作権宣言文
Copyright (C) The Internet Society (2003). All Rights Reserved.
Copyright(C)インターネット協会(2003)。 All rights reserved。
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
それに関するこのドキュメントと翻訳は、コピーして、それが批評するか、またはそうでなければわかる他のもの、および派生している作品に提供するか、または準備されているかもしれなくて、コピーされて、発行されて、全体か一部広げられた実現を助けるかもしれません、どんな種類の制限なしでも、上の版権情報とこのパラグラフがそのようなすべてのコピーと派生している作品の上に含まれていれば。 しかしながら、このドキュメント自体は何らかの方法で変更されないかもしれません、インターネット協会か他のインターネット組織の版権情報か参照を取り除くのなどように、それを英語以外の言語に翻訳するのが著作権のための手順がインターネットStandardsの過程で定義したどのケースに従わなければならないか、必要に応じてさもなければ、インターネット標準を開発する目的に必要であるのを除いて。
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees.
上に承諾された限られた許容は、永久であり、そのインターネット協会、後継者または指定代理人によって取り消されないでしょう。
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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.
このドキュメントとそして、「そのままで」という基礎とインターネットの振興発展を目的とする組織に、インターネット・エンジニアリング・タスク・フォースが速達の、または、暗示しているすべての保証を放棄するかどうかというここにことであり、他を含んでいて、含まれて、情報の使用がここに侵害しないどんな保証も少しもまっすぐになるという情報か市場性か特定目的への適合性のどんな黙示的な保証。
Acknowledgement
承認
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC Editor機能のための基金は現在、インターネット協会によって提供されます。
Yergeau Standards Track [Page 14]
Yergeau標準化過程[14ページ]
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