Ignore:
Timestamp:
Jan 19, 2014, 11:43:53 PM (6 years ago)
Author:
julian.reschke@…
Message:

update rfc2617.xml (ABNF alignment was off from published version), regen all HTML

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1 edited

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  • draft-ietf-httpbis/orig/rfc5234.html

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    316307      <link rel="Help" title="RFC-Editor's Status Page" href="http://www.rfc-editor.org/info/rfc5234">
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    354345      </table>
    355346      <p class="title">Augmented BNF for Syntax Specifications: ABNF</p>
    356       <h1><a id="rfc.status" href="#rfc.status">Status of This Memo</a></h1>
    357       <p>This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions
    358          for improvements. Please refer to the current edition of the “Internet Official Protocol Standards” (STD 1) for the standardization
    359          state and status of this protocol. Distribution of this memo is unlimited.
    360       </p>
    361       <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
     347      <div id="rfc.status">
     348         <h1><a href="#rfc.status">Status of This Memo</a></h1>
     349         <p>This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions
     350            for improvements. Please refer to the current edition of the “Internet Official Protocol Standards” (STD 1) for the standardization
     351            state and status of this protocol. Distribution of this memo is unlimited.
     352         </p>
     353      </div>
     354      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
    362355      <p>Internet technical specifications often need to define a formal syntax. Over the years, a modified version of Backus-Naur
    363356         Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. The current specification documents
     
    365358         and ABNF involve naming rules, repetition, alternatives, order- independence, and value ranges. This specification also supplies
    366359         additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications.
    367       </p> 
     360      </p>
    368361      <hr class="noprint">
    369362      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
    370363      <ul class="toc">
    371          <li>1.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.1">Introduction</a></li>
    372          <li>2.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2">Rule Definition</a><ul>
    373                <li>2.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.1">Rule Naming</a></li>
    374                <li>2.2&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.2">Rule Form</a></li>
    375                <li>2.3&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.3">Terminal Values</a></li>
    376                <li>2.4&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.4">External Encodings</a></li>
     364         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.1">Introduction</a></li>
     365         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2">Rule Definition</a><ul>
     366               <li><a href="#rfc.section.2.1">2.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.1">Rule Naming</a></li>
     367               <li><a href="#rfc.section.2.2">2.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.2">Rule Form</a></li>
     368               <li><a href="#rfc.section.2.3">2.3</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.3">Terminal Values</a></li>
     369               <li><a href="#rfc.section.2.4">2.4</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.2.4">External Encodings</a></li>
    377370            </ul>
    378371         </li>
    379          <li>3.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3">Operators</a><ul>
    380                <li>3.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3.1">Concatenation:  Rule1 Rule2</a></li>
    381                <li>3.2&nbsp;&nbsp;&nbsp;<a href="#Alternatives">Alternatives:  Rule1 / Rule2</a></li>
    382                <li>3.3&nbsp;&nbsp;&nbsp;<a href="#Incremental">Incremental Alternatives: Rule1 =/ Rule2</a></li>
    383                <li>3.4&nbsp;&nbsp;&nbsp;<a href="#Range">Value Range Alternatives:  %c##-##</a></li>
    384                <li>3.5&nbsp;&nbsp;&nbsp;<a href="#Sequence">Sequence Group:  (Rule1 Rule2)</a></li>
    385                <li>3.6&nbsp;&nbsp;&nbsp;<a href="#VarRep">Variable Repetition:  *Rule</a></li>
    386                <li>3.7&nbsp;&nbsp;&nbsp;<a href="#SpecRep">Specific Repetition:  nRule</a></li>
    387                <li>3.8&nbsp;&nbsp;&nbsp;<a href="#OptSeq">Optional Sequence:  [RULE]</a></li>
    388                <li>3.9&nbsp;&nbsp;&nbsp;<a href="#Comment">Comment:  ; Comment</a></li>
    389                <li>3.10&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3.10">Operator Precedence</a></li>
     372         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3">Operators</a><ul>
     373               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3.1">Concatenation:  Rule1 Rule2</a></li>
     374               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#Alternatives">Alternatives:  Rule1 / Rule2</a></li>
     375               <li><a href="#rfc.section.3.3">3.3</a>&nbsp;&nbsp;&nbsp;<a href="#Incremental">Incremental Alternatives: Rule1 =/ Rule2</a></li>
     376               <li><a href="#rfc.section.3.4">3.4</a>&nbsp;&nbsp;&nbsp;<a href="#Range">Value Range Alternatives:  %c##-##</a></li>
     377               <li><a href="#rfc.section.3.5">3.5</a>&nbsp;&nbsp;&nbsp;<a href="#Sequence">Sequence Group:  (Rule1 Rule2)</a></li>
     378               <li><a href="#rfc.section.3.6">3.6</a>&nbsp;&nbsp;&nbsp;<a href="#VarRep">Variable Repetition:  *Rule</a></li>
     379               <li><a href="#rfc.section.3.7">3.7</a>&nbsp;&nbsp;&nbsp;<a href="#SpecRep">Specific Repetition:  nRule</a></li>
     380               <li><a href="#rfc.section.3.8">3.8</a>&nbsp;&nbsp;&nbsp;<a href="#OptSeq">Optional Sequence:  [RULE]</a></li>
     381               <li><a href="#rfc.section.3.9">3.9</a>&nbsp;&nbsp;&nbsp;<a href="#Comment">Comment:  ; Comment</a></li>
     382               <li><a href="#rfc.section.3.10">3.10</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.3.10">Operator Precedence</a></li>
    390383            </ul>
    391384         </li>
    392          <li>4.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.4">ABNF Definition of ABNF</a></li>
    393          <li>5.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.5">Security Considerations</a></li>
    394          <li>6.&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
    395                <li>6.1&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
    396                <li>6.2&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
     385         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.4">ABNF Definition of ABNF</a></li>
     386         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.5">Security Considerations</a></li>
     387         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
     388               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
     389               <li><a href="#rfc.section.6.2">6.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
    397390            </ul>
    398391         </li>
    399392         <li><a href="#rfc.authors">Authors' Addresses</a></li>
    400          <li>A.&nbsp;&nbsp;&nbsp;<a href="#rfc.section.A">Acknowledgements</a></li>
    401          <li>B.&nbsp;&nbsp;&nbsp;<a href="#CORE">Core ABNF of ABNF</a><ul>
    402                <li>B.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.1">Core Rules</a></li>
    403                <li>B.2&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.2">Common Encoding</a></li>
     393         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.A">Acknowledgements</a></li>
     394         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#CORE">Core ABNF of ABNF</a><ul>
     395               <li><a href="#rfc.section.B.1">B.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.1">Core Rules</a></li>
     396               <li><a href="#rfc.section.B.2">B.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.2">Common Encoding</a></li>
    404397            </ul>
    405398         </li>
    406399         <li><a href="#rfc.ipr">Intellectual Property and Copyright Statements</a></li>
    407400      </ul>
    408       <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;Introduction
    409       </h1>
    410       <p id="rfc.section.1.p.1">Internet technical specifications often need to define a formal syntax and are free to employ whatever notation their authors
    411          deem useful. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among
    412          many Internet specifications. It balances compactness and simplicity with reasonable representational power. In the early
    413          days of the Arpanet, each specification contained its own definition of ABNF. This included the email specifications, <a href="#RFC733"><cite title="Standard for the format of ARPA network text messages">[RFC733]</cite></a> and then <a href="#RFC822"><cite title="Standard for the format of ARPA Internet text messages">[RFC822]</cite></a>, which came to be the common citations for defining ABNF. The current document separates those definitions to permit selective
    414          reference. Predictably, it also provides some modifications and enhancements.
    415       </p>
    416       <p id="rfc.section.1.p.2">The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value
    417          ranges. <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a> supplies rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications.
    418          It is provided as a convenience and is otherwise separate from the meta language defined in the body of this document, and
    419          separate from its formal status.
    420       </p>
    421       <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;Rule Definition
    422       </h1>
    423       <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;Rule Naming
    424       </h2>
    425       <p id="rfc.section.2.1.p.1">The name of a rule is simply the name itself, that is, a sequence of characters, beginning with an alphabetic character, and
    426          followed by a combination of alphabetics, digits, and hyphens (dashes).
    427       </p>
    428       <p id="rfc.section.2.1.p.2"> </p>
    429       <dl>
    430          <dt>NOTE:  </dt>
    431          <dd>Rule names are case insensitive.</dd>
    432       </dl>
    433       <p id="rfc.section.2.1.p.3">The names &lt;rulename&gt;, &lt;Rulename&gt;, &lt;RULENAME&gt;, and &lt;rUlENamE&gt; all refer to the same rule.</p>
    434       <p id="rfc.section.2.1.p.4">Unlike original BNF, angle brackets ("&lt;", "&gt;") are not required. However, angle brackets may be used around a rule name whenever
    435          their presence facilitates in discerning the use of a rule name. This is typically restricted to rule name references in free-form
    436          prose, or to distinguish partial rules that combine into a string not separated by white space, such as shown in the discussion
    437          about repetition, below.
    438       </p>
    439       <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;Rule Form
    440       </h2>
    441       <p id="rfc.section.2.2.p.1">A rule is defined by the following sequence:</p>
    442       <div id="rfc.figure.u.1"></div> <pre>
    443       name =  elements crlf </pre> <p id="rfc.section.2.2.p.3">where &lt;name&gt; is the name of the rule, &lt;elements&gt; is one or more rule names or terminal specifications, and &lt;crlf&gt; is the end-of-line
    444          indicator (carriage return followed by line feed). The equal sign separates the name from the definition of the rule. The
    445          elements form a sequence of one or more rule names and/or value definitions, combined according to the various operators defined
    446          in this document, such as alternative and repetition.
    447       </p>
    448       <p id="rfc.section.2.2.p.4">For visual ease, rule definitions are left aligned. When a rule requires multiple lines, the continuation lines are indented.
    449          The left alignment and indentation are relative to the first lines of the ABNF rules and need not match the left margin of
    450          the document.
    451       </p>
    452       <h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;Terminal Values
    453       </h2>
    454       <p id="rfc.section.2.3.p.1">Rules resolve into a string of terminal values, sometimes called characters. In ABNF, a character is merely a non-negative
    455          integer. In certain contexts, a specific mapping (encoding) of values into a character set (such as ASCII) will be specified.
    456       </p>
    457       <div id="rfc.figure.u.2"></div>
    458       <p>Terminals are specified by one or more numeric characters, with the base interpretation of those characters indicated explicitly.
    459          The following bases are currently defined:
    460       </p>  <pre>
     401      <div>
     402         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;Introduction
     403         </h1>
     404         <p id="rfc.section.1.p.1">Internet technical specifications often need to define a formal syntax and are free to employ whatever notation their authors
     405            deem useful. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among
     406            many Internet specifications. It balances compactness and simplicity with reasonable representational power. In the early
     407            days of the Arpanet, each specification contained its own definition of ABNF. This included the email specifications, <a href="#RFC733"><cite title="Standard for the format of ARPA network text messages">[RFC733]</cite></a> and then <a href="#RFC822"><cite title="Standard for the format of ARPA Internet text messages">[RFC822]</cite></a>, which came to be the common citations for defining ABNF. The current document separates those definitions to permit selective
     408            reference. Predictably, it also provides some modifications and enhancements.
     409         </p>
     410         <p id="rfc.section.1.p.2">The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value
     411            ranges. <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a> supplies rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications.
     412            It is provided as a convenience and is otherwise separate from the meta language defined in the body of this document, and
     413            separate from its formal status.
     414         </p>
     415      </div>
     416      <div>
     417         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;Rule Definition
     418         </h1>
     419         <div>
     420            <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;Rule Naming
     421            </h2>
     422            <p id="rfc.section.2.1.p.1">The name of a rule is simply the name itself, that is, a sequence of characters, beginning with an alphabetic character, and
     423               followed by a combination of alphabetics, digits, and hyphens (dashes).
     424            </p>
     425            <p id="rfc.section.2.1.p.2"></p>
     426            <dl>
     427               <dt>NOTE:  </dt>
     428               <dd>Rule names are case insensitive.</dd>
     429            </dl>
     430            <p id="rfc.section.2.1.p.3">The names &lt;rulename&gt;, &lt;Rulename&gt;, &lt;RULENAME&gt;, and &lt;rUlENamE&gt; all refer to the same rule.</p>
     431            <p id="rfc.section.2.1.p.4">Unlike original BNF, angle brackets ("&lt;", "&gt;") are not required. However, angle brackets may be used around a rule name whenever
     432               their presence facilitates in discerning the use of a rule name. This is typically restricted to rule name references in free-form
     433               prose, or to distinguish partial rules that combine into a string not separated by white space, such as shown in the discussion
     434               about repetition, below.
     435            </p>
     436         </div>
     437         <div>
     438            <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;Rule Form
     439            </h2>
     440            <p id="rfc.section.2.2.p.1">A rule is defined by the following sequence:</p>
     441            <div id="rfc.figure.u.1"></div><pre>
     442      name =  elements crlf </pre><p id="rfc.section.2.2.p.3">where &lt;name&gt; is the name of the rule, &lt;elements&gt; is one or more rule names or terminal specifications, and &lt;crlf&gt; is the end-of-line
     443               indicator (carriage return followed by line feed). The equal sign separates the name from the definition of the rule. The
     444               elements form a sequence of one or more rule names and/or value definitions, combined according to the various operators defined
     445               in this document, such as alternative and repetition.
     446            </p>
     447            <p id="rfc.section.2.2.p.4">For visual ease, rule definitions are left aligned. When a rule requires multiple lines, the continuation lines are indented.
     448               The left alignment and indentation are relative to the first lines of the ABNF rules and need not match the left margin of
     449               the document.
     450            </p>
     451         </div>
     452         <div>
     453            <h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;Terminal Values
     454            </h2>
     455            <p id="rfc.section.2.3.p.1">Rules resolve into a string of terminal values, sometimes called characters. In ABNF, a character is merely a non-negative
     456               integer. In certain contexts, a specific mapping (encoding) of values into a character set (such as ASCII) will be specified.
     457            </p>
     458            <div id="rfc.figure.u.2"></div>
     459            <p>Terminals are specified by one or more numeric characters, with the base interpretation of those characters indicated explicitly.
     460               The following bases are currently defined:
     461            </p><pre>
    461462      b           =  binary
    462463
    463464      d           =  decimal
    464465
    465       x           =  hexadecimal </pre> <div id="rfc.figure.u.3"></div>
    466       <p>Hence:</p>  <pre>
     466      x           =  hexadecimal </pre><div id="rfc.figure.u.3"></div>
     467            <p>Hence:</p><pre>
    467468      CR          =  %d13
    468469
    469470      CR          =  %x0D
    470 </pre>  <p>respectively specify the decimal and hexadecimal representation of <a href="#US-ASCII"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[US-ASCII]</cite></a> for carriage return.
    471       </p>
    472       <div id="rfc.figure.u.4"></div>
    473       <p>A concatenated string of such values is specified compactly, using a period (".") to indicate a separation of characters within
    474          that value. Hence:
    475       </p>  <pre>
    476       CRLF        =  %d13.10 </pre> <div id="rfc.figure.u.5"></div>
    477       <p>ABNF permits the specification of literal text strings directly, enclosed in quotation marks. Hence:</p>  <pre>
    478       command     =  "command string" </pre> <p id="rfc.section.2.3.p.6">Literal text strings are interpreted as a concatenated set of printable characters.</p>
    479       <p id="rfc.section.2.3.p.7"> </p>
    480       <dl>
    481          <dt>NOTE:  </dt>
    482          <dd>ABNF strings are case insensitive and the character set for these strings is US-ASCII.</dd>
    483       </dl>
    484       <div id="rfc.figure.u.6"></div>
    485       <p>Hence:</p>  <pre>
    486       rulename = "abc" </pre> <div id="rfc.figure.u.7"></div>
    487       <p>and:</p>  <pre>
     471</pre><p>respectively specify the decimal and hexadecimal representation of <a href="#US-ASCII"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[US-ASCII]</cite></a> for carriage return.
     472            </p>
     473            <div id="rfc.figure.u.4"></div>
     474            <p>A concatenated string of such values is specified compactly, using a period (".") to indicate a separation of characters within
     475               that value. Hence:
     476            </p><pre>
     477      CRLF        =  %d13.10 </pre><div id="rfc.figure.u.5"></div>
     478            <p>ABNF permits the specification of literal text strings directly, enclosed in quotation marks. Hence:</p><pre>
     479      command     =  "command string" </pre><p id="rfc.section.2.3.p.6">Literal text strings are interpreted as a concatenated set of printable characters.</p>
     480            <p id="rfc.section.2.3.p.7"></p>
     481            <dl>
     482               <dt>NOTE:  </dt>
     483               <dd>ABNF strings are case insensitive and the character set for these strings is US-ASCII.</dd>
     484            </dl>
     485            <div id="rfc.figure.u.6"></div>
     486            <p>Hence:</p><pre>
     487      rulename = "abc" </pre><div id="rfc.figure.u.7"></div>
     488            <p>and:</p><pre>
    488489      rulename = "aBc"
    489 </pre>  <p>will match "abc", "Abc", "aBc", "abC", "ABc", "aBC", "AbC", and "ABC".</p>
    490       <p id="rfc.section.2.3.p.10"> </p>
    491       <ul class="empty">
    492          <li>To specify a rule that is case sensitive, specify the characters individually.</li>
    493       </ul>
    494       <div id="rfc.figure.u.8"></div>
    495       <p>For example:</p>  <pre>
     490</pre><p>will match "abc", "Abc", "aBc", "abC", "ABc", "aBC", "AbC", and "ABC".</p>
     491            <p id="rfc.section.2.3.p.10"></p>
     492            <ul class="empty">
     493               <li>To specify a rule that is case sensitive, specify the characters individually.</li>
     494            </ul>
     495            <div id="rfc.figure.u.8"></div>
     496            <p>For example:</p><pre>
    496497      rulename    =  %d97 %d98 %d99
    497 </pre> <div id="rfc.figure.u.9"></div>
    498       <p>or</p>  <pre>
     498</pre><div id="rfc.figure.u.9"></div>
     499            <p>or</p><pre>
    499500      rulename    =  %d97.98.99
    500 </pre>  <p>will match only the string that comprises only the lowercase characters, abc.</p>
    501       <h2 id="rfc.section.2.4"><a href="#rfc.section.2.4">2.4</a>&nbsp;External Encodings
    502       </h2>
    503       <p id="rfc.section.2.4.p.1">External representations of terminal value characters will vary according to constraints in the storage or transmission environment.
    504          Hence, the same ABNF-based grammar may have multiple external encodings, such as one for a 7-bit US-ASCII environment, another
    505          for a binary octet environment, and still a different one when 16-bit Unicode is used. Encoding details are beyond the scope
    506          of ABNF, although <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a> provides definitions for a 7-bit US-ASCII environment as has been common to much of the Internet.
    507       </p>
    508       <p id="rfc.section.2.4.p.2">By separating external encoding from the syntax, it is intended that alternate encoding environments can be used for the same
    509          syntax.
    510       </p>
    511       <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;Operators
    512       </h1>
    513       <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;Concatenation:  Rule1 Rule2
    514       </h2>
    515       <p id="rfc.section.3.1.p.1">A rule can define a simple, ordered string of values (i.e., a concatenation of contiguous characters) by listing a sequence
    516          of rule names. For example:
    517       </p>
    518       <div id="rfc.figure.u.10"></div> <pre>
     501</pre><p>will match only the string that comprises only the lowercase characters, abc.</p>
     502         </div>
     503         <div>
     504            <h2 id="rfc.section.2.4"><a href="#rfc.section.2.4">2.4</a>&nbsp;External Encodings
     505            </h2>
     506            <p id="rfc.section.2.4.p.1">External representations of terminal value characters will vary according to constraints in the storage or transmission environment.
     507               Hence, the same ABNF-based grammar may have multiple external encodings, such as one for a 7-bit US-ASCII environment, another
     508               for a binary octet environment, and still a different one when 16-bit Unicode is used. Encoding details are beyond the scope
     509               of ABNF, although <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a> provides definitions for a 7-bit US-ASCII environment as has been common to much of the Internet.
     510            </p>
     511            <p id="rfc.section.2.4.p.2">By separating external encoding from the syntax, it is intended that alternate encoding environments can be used for the same
     512               syntax.
     513            </p>
     514         </div>
     515      </div>
     516      <div>
     517         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;Operators
     518         </h1>
     519         <div>
     520            <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;Concatenation:  Rule1 Rule2
     521            </h2>
     522            <p id="rfc.section.3.1.p.1">A rule can define a simple, ordered string of values (i.e., a concatenation of contiguous characters) by listing a sequence
     523               of rule names. For example:
     524            </p>
     525            <div id="rfc.figure.u.10"></div><pre>
    519526      foo         =  %x61           ; a
    520527
    521528      bar         =  %x62           ; b
    522529
    523       mumble      =  foo bar foo </pre> <p id="rfc.section.3.1.p.3">So that the rule &lt;mumble&gt; matches the lowercase string "aba".</p>
    524       <p id="rfc.section.3.1.p.4">Linear white space: Concatenation is at the core of the ABNF parsing model. A string of contiguous characters (values) is
    525          parsed according to the rules defined in ABNF. For Internet specifications, there is some history of permitting linear white
    526          space (space and horizontal tab) to be freely and implicitly interspersed around major constructs, such as delimiting special
    527          characters or atomic strings.
    528       </p>
    529       <p id="rfc.section.3.1.p.5">NOTE: </p>
    530       <ul class="empty">
    531          <li>This specification for ABNF does not provide for implicit specification of linear white space.</li>
    532       </ul>
    533       <p id="rfc.section.3.1.p.6">Any grammar that wishes to permit linear white space around delimiters or string segments must specify it explicitly. It is
    534          often useful to provide for such white space in "core" rules that are then used variously among higher-level rules. The "core"
    535          rules might be formed into a lexical analyzer or simply be part of the main ruleset.
    536       </p>
    537       <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="Alternatives" href="#Alternatives">Alternatives:  Rule1 / Rule2</a></h2>
    538       <p id="rfc.section.3.2.p.1">Elements separated by a forward slash ("/") are alternatives. Therefore,</p>
    539       <div id="rfc.figure.u.11"></div> <pre>
     530      mumble      =  foo bar foo </pre><p id="rfc.section.3.1.p.3">So that the rule &lt;mumble&gt; matches the lowercase string "aba".</p>
     531            <p id="rfc.section.3.1.p.4">Linear white space: Concatenation is at the core of the ABNF parsing model. A string of contiguous characters (values) is
     532               parsed according to the rules defined in ABNF. For Internet specifications, there is some history of permitting linear white
     533               space (space and horizontal tab) to be freely and implicitly interspersed around major constructs, such as delimiting special
     534               characters or atomic strings.
     535            </p>
     536            <p id="rfc.section.3.1.p.5">NOTE: </p>
     537            <ul class="empty">
     538               <li>This specification for ABNF does not provide for implicit specification of linear white space.</li>
     539            </ul>
     540            <p id="rfc.section.3.1.p.6">Any grammar that wishes to permit linear white space around delimiters or string segments must specify it explicitly. It is
     541               often useful to provide for such white space in "core" rules that are then used variously among higher-level rules. The "core"
     542               rules might be formed into a lexical analyzer or simply be part of the main ruleset.
     543            </p>
     544         </div>
     545         <div id="Alternatives">
     546            <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a href="#Alternatives">Alternatives:  Rule1 / Rule2</a></h2>
     547            <p id="rfc.section.3.2.p.1">Elements separated by a forward slash ("/") are alternatives. Therefore,</p>
     548            <div id="rfc.figure.u.11"></div><pre>
    540549      foo / bar 
    541 </pre>  <p>will accept &lt;foo&gt; or &lt;bar&gt;.</p>
    542       <p id="rfc.section.3.2.p.3"> </p>
    543       <dl>
    544          <dt>NOTE:  </dt>
    545          <dd>A quoted string containing alphabetic characters is a special form for specifying alternative characters and is interpreted
    546             as a non-terminal representing the set of combinatorial strings with the contained characters, in the specified order but
    547             with any mixture of upper- and lowercase.
    548          </dd>
    549       </dl>
    550       <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a id="Incremental" href="#Incremental">Incremental Alternatives: Rule1 =/ Rule2</a></h2>
    551       <p id="rfc.section.3.3.p.1">It is sometimes convenient to specify a list of alternatives in fragments. That is, an initial rule may match one or more
    552          alternatives, with later rule definitions adding to the set of alternatives. This is particularly useful for otherwise independent
    553          specifications that derive from the same parent ruleset, such as often occurs with parameter lists. ABNF permits this incremental
    554          definition through the construct:
    555       </p>
    556       <div id="rfc.figure.u.12"></div> <pre>
    557       oldrule     =/ additional-alternatives </pre> <div id="rfc.figure.u.13"></div>
    558       <p>So that the ruleset</p>  <pre>
     550</pre><p>will accept &lt;foo&gt; or &lt;bar&gt;.</p>
     551            <p id="rfc.section.3.2.p.3"></p>
     552            <dl>
     553               <dt>NOTE:  </dt>
     554               <dd>A quoted string containing alphabetic characters is a special form for specifying alternative characters and is interpreted
     555                  as a non-terminal representing the set of combinatorial strings with the contained characters, in the specified order but
     556                  with any mixture of upper- and lowercase.
     557               </dd>
     558            </dl>
     559         </div>
     560         <div id="Incremental">
     561            <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a href="#Incremental">Incremental Alternatives: Rule1 =/ Rule2</a></h2>
     562            <p id="rfc.section.3.3.p.1">It is sometimes convenient to specify a list of alternatives in fragments. That is, an initial rule may match one or more
     563               alternatives, with later rule definitions adding to the set of alternatives. This is particularly useful for otherwise independent
     564               specifications that derive from the same parent ruleset, such as often occurs with parameter lists. ABNF permits this incremental
     565               definition through the construct:
     566            </p>
     567            <div id="rfc.figure.u.12"></div><pre>
     568      oldrule     =/ additional-alternatives </pre><div id="rfc.figure.u.13"></div>
     569            <p>So that the ruleset</p><pre>
    559570      ruleset     =  alt1 / alt2
    560571
    561572      ruleset     =/ alt3
    562573
    563       ruleset     =/ alt4 / alt5 </pre> <div id="rfc.figure.u.14"></div>
    564       <p>is the same as specifying</p>  <pre>
    565       ruleset     =  alt1 / alt2 / alt3 / alt4 / alt5 </pre> <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a id="Range" href="#Range">Value Range Alternatives:  %c##-##</a></h2>
    566       <div id="rfc.figure.u.15"></div>
    567       <p>A range of alternative numeric values can be specified compactly, using a dash ("-") to indicate the range of alternative
    568          values. Hence:
    569       </p>  <pre>
    570       DIGIT       =  %x30-39 </pre> <div id="rfc.figure.u.16"></div>
    571       <p>is equivalent to:</p>  <pre>
     574      ruleset     =/ alt4 / alt5 </pre><div id="rfc.figure.u.14"></div>
     575            <p>is the same as specifying</p><pre>
     576      ruleset     =  alt1 / alt2 / alt3 / alt4 / alt5 </pre></div>
     577         <div id="Range">
     578            <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a href="#Range">Value Range Alternatives:  %c##-##</a></h2>
     579            <div id="rfc.figure.u.15"></div>
     580            <p>A range of alternative numeric values can be specified compactly, using a dash ("-") to indicate the range of alternative
     581               values. Hence:
     582            </p><pre>
     583      DIGIT       =  %x30-39 </pre><div id="rfc.figure.u.16"></div>
     584            <p>is equivalent to:</p><pre>
    572585      DIGIT       =  "0" / "1" / "2" / "3" / "4" / "5" / "6" /
    573586
    574                      "7" / "8" / "9" </pre> <div id="rfc.figure.u.17"></div>
    575       <p>Concatenated numeric values and numeric value ranges cannot be specified in the same string. A numeric value may use the dotted
    576          notation for concatenation or it may use the dash notation to specify one value range. Hence, to specify one printable character
    577          between end-of-line sequences, the specification could be:
    578       </p>  <pre>
    579       char-line = %x0D.0A %x20-7E %x0D.0A </pre> <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a>&nbsp;<a id="Sequence" href="#Sequence">Sequence Group:  (Rule1 Rule2)</a></h2>
    580       <div id="rfc.figure.u.18"></div>
    581       <p>Elements enclosed in parentheses are treated as a single element, whose contents are strictly ordered. Thus,</p>  <pre>
     587                     "7" / "8" / "9" </pre><div id="rfc.figure.u.17"></div>
     588            <p>Concatenated numeric values and numeric value ranges cannot be specified in the same string. A numeric value may use the dotted
     589               notation for concatenation or it may use the dash notation to specify one value range. Hence, to specify one printable character
     590               between end-of-line sequences, the specification could be:
     591            </p><pre>
     592      char-line = %x0D.0A %x20-7E %x0D.0A </pre></div>
     593         <div id="Sequence">
     594            <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a>&nbsp;<a href="#Sequence">Sequence Group:  (Rule1 Rule2)</a></h2>
     595            <div id="rfc.figure.u.18"></div>
     596            <p>Elements enclosed in parentheses are treated as a single element, whose contents are strictly ordered. Thus,</p><pre>
    582597      elem (foo / bar) blat
    583 </pre>  <p>matches (elem foo blat) or (elem bar blat), and</p>
    584       <div id="rfc.figure.u.19"></div> <pre>
     598</pre><p>matches (elem foo blat) or (elem bar blat), and</p>
     599            <div id="rfc.figure.u.19"></div><pre>
    585600      elem foo / bar blat
    586 </pre>  <p>matches (elem foo) or (bar blat).</p>
    587       <p id="rfc.section.3.5.p.3"> </p>
    588       <dl>
    589          <dt>NOTE:  </dt>
    590          <dd>It is strongly advised that grouping notation be used, rather than relying on the proper reading of "bare" alternations, when
    591             alternatives consist of multiple rule names or literals.
    592          </dd>
    593       </dl>
    594       <div id="rfc.figure.u.20"></div>
    595       <p>Hence, it is recommended that the following form be used:</p>  <pre>
     601</pre><p>matches (elem foo) or (bar blat).</p>
     602            <p id="rfc.section.3.5.p.3"></p>
     603            <dl>
     604               <dt>NOTE:  </dt>
     605               <dd>It is strongly advised that grouping notation be used, rather than relying on the proper reading of "bare" alternations, when
     606                  alternatives consist of multiple rule names or literals.
     607               </dd>
     608            </dl>
     609            <div id="rfc.figure.u.20"></div>
     610            <p>Hence, it is recommended that the following form be used:</p><pre>
    596611     (elem foo) / (bar blat)
    597 </pre>  <p>It will avoid misinterpretation by casual readers.</p>
    598       <p id="rfc.section.3.5.p.5">The sequence group notation is also used within free text to set off an element sequence from the prose.</p>
    599       <h2 id="rfc.section.3.6"><a href="#rfc.section.3.6">3.6</a>&nbsp;<a id="VarRep" href="#VarRep">Variable Repetition:  *Rule</a></h2>
    600       <div id="rfc.figure.u.21"></div>
    601       <p>The operator "*" preceding an element indicates repetition. The full form is:</p>  <pre>
     612</pre><p>It will avoid misinterpretation by casual readers.</p>
     613            <p id="rfc.section.3.5.p.5">The sequence group notation is also used within free text to set off an element sequence from the prose.</p>
     614         </div>
     615         <div id="VarRep">
     616            <h2 id="rfc.section.3.6"><a href="#rfc.section.3.6">3.6</a>&nbsp;<a href="#VarRep">Variable Repetition:  *Rule</a></h2>
     617            <div id="rfc.figure.u.21"></div>
     618            <p>The operator "*" preceding an element indicates repetition. The full form is:</p><pre>
    602619      &lt;a&gt;*&lt;b&gt;element
    603 </pre>  <p>where &lt;a&gt; and &lt;b&gt; are optional decimal values, indicating at least &lt;a&gt; and at most &lt;b&gt; occurrences of the element.</p>
    604       <p id="rfc.section.3.6.p.2">Default values are 0 and infinity so that *&lt;element&gt; allows any number, including zero; 1*&lt;element&gt; requires at least one;
    605          3*3&lt;element&gt; allows exactly 3; and 1*2&lt;element&gt; allows one or two.
    606       </p>
    607       <h2 id="rfc.section.3.7"><a href="#rfc.section.3.7">3.7</a>&nbsp;<a id="SpecRep" href="#SpecRep">Specific Repetition:  nRule</a></h2>
    608       <div id="rfc.figure.u.22"></div>
    609       <p>A rule of the form:</p>  <pre>
    610       &lt;n&gt;element </pre> <div id="rfc.figure.u.23"></div>
    611       <p>is equivalent to</p>  <pre>
    612       &lt;n&gt;*&lt;n&gt;element </pre> <p id="rfc.section.3.7.p.3">That is, exactly &lt;n&gt; occurrences of &lt;element&gt;. Thus, 2DIGIT is a 2-digit number, and 3ALPHA is a string of three alphabetic
    613          characters.
    614       </p>
    615       <h2 id="rfc.section.3.8"><a href="#rfc.section.3.8">3.8</a>&nbsp;<a id="OptSeq" href="#OptSeq">Optional Sequence:  [RULE]</a></h2>
    616       <div id="rfc.figure.u.24"></div>
    617       <p>Square brackets enclose an optional element sequence:</p>  <pre>
    618       [foo bar] </pre> <div id="rfc.figure.u.25"></div>
    619       <p>is equivalent to</p>  <pre>
    620       *1(foo bar). </pre> <h2 id="rfc.section.3.9"><a href="#rfc.section.3.9">3.9</a>&nbsp;<a id="Comment" href="#Comment">Comment:  ; Comment</a></h2>
    621       <p id="rfc.section.3.9.p.1">A semicolon starts a comment that continues to the end of line. This is a simple way of including useful notes in parallel
    622          with the specifications.
    623       </p>
    624       <h2 id="rfc.section.3.10"><a href="#rfc.section.3.10">3.10</a>&nbsp;Operator Precedence
    625       </h2>
    626       <p id="rfc.section.3.10.p.1">The various mechanisms described above have the following precedence, from highest (binding tightest) at the top, to lowest
    627          (loosest) at the bottom:
    628       </p>
    629       <ul class="empty">
    630          <li>Rule name, prose-val, Terminal value</li>
    631          <li>Comment</li>
    632          <li>Value range</li>
    633          <li>Repetition</li>
    634          <li>Grouping, Optional</li>
    635          <li>Concatenation</li>
    636          <li>Alternative</li>
    637       </ul>
    638       <p id="rfc.section.3.10.p.2">Use of the alternative operator, freely mixed with concatenations, can be confusing.</p>
    639       <p id="rfc.section.3.10.p.3"> </p>
    640       <ul class="empty">
    641          <li>Again, it is recommended that the grouping operator be used to make explicit concatenation groups.</li>
    642       </ul>
    643       <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;ABNF Definition of ABNF
    644       </h1>
    645       <p id="rfc.section.4.p.1"> </p>
    646       <dl>
    647          <dt>NOTES:</dt>
    648          <dd>
    649             <ol>
    650                <li>This syntax requires a formatting of rules that is relatively strict. Hence, the version of a ruleset included in a specification
    651                   might need preprocessing to ensure that it can be interpreted by an ABNF parser.
    652                </li>
    653                <li>This syntax uses the rules provided in <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a>.
    654                </li>
    655             </ol>
    656          </dd>
    657       </dl>
    658       <div id="rfc.figure.u.26"></div> <pre class="inline">
     620</pre><p>where &lt;a&gt; and &lt;b&gt; are optional decimal values, indicating at least &lt;a&gt; and at most &lt;b&gt; occurrences of the element.</p>
     621            <p id="rfc.section.3.6.p.2">Default values are 0 and infinity so that *&lt;element&gt; allows any number, including zero; 1*&lt;element&gt; requires at least one;
     622               3*3&lt;element&gt; allows exactly 3; and 1*2&lt;element&gt; allows one or two.
     623            </p>
     624         </div>
     625         <div id="SpecRep">
     626            <h2 id="rfc.section.3.7"><a href="#rfc.section.3.7">3.7</a>&nbsp;<a href="#SpecRep">Specific Repetition:  nRule</a></h2>
     627            <div id="rfc.figure.u.22"></div>
     628            <p>A rule of the form:</p><pre>
     629      &lt;n&gt;element </pre><div id="rfc.figure.u.23"></div>
     630            <p>is equivalent to</p><pre>
     631      &lt;n&gt;*&lt;n&gt;element </pre><p id="rfc.section.3.7.p.3">That is, exactly &lt;n&gt; occurrences of &lt;element&gt;. Thus, 2DIGIT is a 2-digit number, and 3ALPHA is a string of three alphabetic
     632               characters.
     633            </p>
     634         </div>
     635         <div id="OptSeq">
     636            <h2 id="rfc.section.3.8"><a href="#rfc.section.3.8">3.8</a>&nbsp;<a href="#OptSeq">Optional Sequence:  [RULE]</a></h2>
     637            <div id="rfc.figure.u.24"></div>
     638            <p>Square brackets enclose an optional element sequence:</p><pre>
     639      [foo bar] </pre><div id="rfc.figure.u.25"></div>
     640            <p>is equivalent to</p><pre>
     641      *1(foo bar). </pre></div>
     642         <div id="Comment">
     643            <h2 id="rfc.section.3.9"><a href="#rfc.section.3.9">3.9</a>&nbsp;<a href="#Comment">Comment:  ; Comment</a></h2>
     644            <p id="rfc.section.3.9.p.1">A semicolon starts a comment that continues to the end of line. This is a simple way of including useful notes in parallel
     645               with the specifications.
     646            </p>
     647         </div>
     648         <div>
     649            <h2 id="rfc.section.3.10"><a href="#rfc.section.3.10">3.10</a>&nbsp;Operator Precedence
     650            </h2>
     651            <p id="rfc.section.3.10.p.1">The various mechanisms described above have the following precedence, from highest (binding tightest) at the top, to lowest
     652               (loosest) at the bottom:
     653            </p>
     654            <ul class="empty">
     655               <li>Rule name, prose-val, Terminal value</li>
     656               <li>Comment</li>
     657               <li>Value range</li>
     658               <li>Repetition</li>
     659               <li>Grouping, Optional</li>
     660               <li>Concatenation</li>
     661               <li>Alternative</li>
     662            </ul>
     663            <p id="rfc.section.3.10.p.2">Use of the alternative operator, freely mixed with concatenations, can be confusing.</p>
     664            <p id="rfc.section.3.10.p.3"></p>
     665            <ul class="empty">
     666               <li>Again, it is recommended that the grouping operator be used to make explicit concatenation groups.</li>
     667            </ul>
     668         </div>
     669      </div>
     670      <div>
     671         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;ABNF Definition of ABNF
     672         </h1>
     673         <p id="rfc.section.4.p.1"></p>
     674         <dl>
     675            <dt>NOTES:</dt>
     676            <dd>
     677               <ol>
     678                  <li>This syntax requires a formatting of rules that is relatively strict. Hence, the version of a ruleset included in a specification
     679                     might need preprocessing to ensure that it can be interpreted by an ABNF parser.
     680                  </li>
     681                  <li>This syntax uses the rules provided in <a href="#CORE" title="Core ABNF of ABNF">Appendix&nbsp;B</a>.
     682                  </li>
     683               </ol>
     684            </dd>
     685         </dl>
     686         <div id="rfc.figure.u.26"></div><pre class="inline">
    659687      rulelist       =  1*( rule / (*c-wsp c-nl) )
    660688
     
    718746                             ;  without angles
    719747                             ; prose description, to be used as
    720                              ;  last resort </pre> <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;Security Considerations
    721       </h1>
    722       <p id="rfc.section.5.p.1">Security is truly believed to be irrelevant to this document.</p>
     748                             ;  last resort </pre></div>
     749      <div>
     750         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;Security Considerations
     751         </h1>
     752         <p id="rfc.section.5.p.1">Security is truly believed to be irrelevant to this document.</p>
     753      </div>
    723754      <h1 id="rfc.references"><a id="rfc.section.6" href="#rfc.section.6">6.</a> References
    724755      </h1>
    725756      <h2 id="rfc.references.1"><a href="#rfc.section.6.1" id="rfc.section.6.1">6.1</a> Normative References
    726757      </h2>
    727       <table> 
     758      <table>
    728759         <tr>
    729760            <td class="reference"><b id="US-ASCII">[US-ASCII]</b></td>
     
    735766      <h2 id="rfc.references.2"><a href="#rfc.section.6.2" id="rfc.section.6.2">6.2</a> Informative References
    736767      </h2>
    737       <table>   
     768      <table>
    738769         <tr>
    739770            <td class="reference"><b id="RFC733">[RFC733]</b></td>
     
    749780      <div class="avoidbreak">
    750781         <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
    751          <address class="vcard"><span class="vcardline"><span class="fn">Dave Crocker</span>
    752                (editor)
    753                <span class="n hidden"><span class="family-name">Crocker</span><span class="given-name">Dave</span></span></span><span class="org vcardline">Brandenburg InternetWorking</span><span class="adr"><span class="street-address vcardline">675 Spruce Dr.</span><span class="vcardline"><span class="locality">Sunnyvale</span>, <span class="region">CA</span>&nbsp;<span class="postal-code">94086</span></span><span class="country-name vcardline">US</span></span><span class="vcardline tel">Phone: <a href="tel:+1.408.246.8253"><span class="value">+1.408.246.8253</span></a></span><span class="vcardline">Email: <a href="mailto:dcrocker@bbiw.net"><span class="email">dcrocker@bbiw.net</span></a></span></address>
    754          <address class="vcard"><span class="vcardline"><span class="fn">Paul Overell</span><span class="n hidden"><span class="family-name">Overell</span><span class="given-name">Paul</span></span></span><span class="org vcardline">THUS plc.</span><span class="adr"><span class="street-address vcardline">1/2 Berkeley Square,</span><span class="street-address vcardline">99 Berkeley Street</span><span class="vcardline"><span class="locality">Glasgow</span>, <span class="postal-code">G3 7HR</span></span><span class="country-name vcardline">UK</span></span><span class="vcardline">Email: <a href="mailto:paul.overell@thus.net"><span class="email">paul.overell@thus.net</span></a></span></address>
     782         <p><b>Dave Crocker</b>
     783            (editor)
     784            <br>Brandenburg InternetWorking<br>675 Spruce Dr.<br>Sunnyvale, CA&nbsp;94086<br>US<br>Phone: <a href="tel:+1.408.246.8253">+1.408.246.8253</a><br>Email: <a href="mailto:dcrocker@bbiw.net">dcrocker@bbiw.net</a></p>
     785         <p><b>Paul Overell</b><br>THUS plc.<br>1/2 Berkeley Square,<br>99 Berkeley Street<br>Glasgow, G3 7HR<br>UK<br>Email: <a href="mailto:paul.overell@thus.net">paul.overell@thus.net</a></p>
    755786      </div>
    756       <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;Acknowledgements
    757       </h1>
    758       <p id="rfc.section.A.p.1">The syntax for ABNF was originally specified in RFC 733. Ken L. Harrenstien, of SRI International, was responsible for re-coding
    759          the BNF into an Augmented BNF that makes the representation smaller and easier to understand.
    760       </p>
    761       <p id="rfc.section.A.p.2">This recent project began as a simple effort to cull out the portion of RFC 822 that has been repeatedly cited by non-email
    762          specification writers, namely the description of Augmented BNF. Rather than simply and blindly converting the existing text
    763          into a separate document, the working group chose to give careful consideration to the deficiencies, as well as benefits,
    764          of the existing specification and related specifications made available over the last 15 years, and therefore to pursue enhancement.
    765          This turned the project into something rather more ambitious than was first intended. Interestingly, the result is not massively
    766          different from that original, although decisions, such as removing the list notation, came as a surprise.
    767       </p>
    768       <p id="rfc.section.A.p.3">This "separated" version of the specification was part of the DRUMS working group, with significant contributions from Jerome
    769          Abela, Harald Alvestrand, Robert Elz, Roger Fajman, Aviva Garrett, Tom Harsch, Dan Kohn, Bill McQuillan, Keith Moore, Chris
    770          Newman, Pete Resnick, and Henning Schulzrinne.
    771       </p>
    772       <p id="rfc.section.A.p.4">Julian Reschke warrants a special thanks for converting the Draft Standard version to XML source form.</p>
    773       <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a id="CORE" href="#CORE">Core ABNF of ABNF</a></h1>
    774       <p id="rfc.section.B.p.1">This appendix contains some basic rules that are in common use. Basic rules are in uppercase. Note that these rules are only
    775          valid for ABNF encoded in 7-bit ASCII or in characters sets that are a superset of 7-bit ASCII.
    776       </p>
    777       <h2 id="rfc.section.B.1"><a href="#rfc.section.B.1">B.1</a>&nbsp;Core Rules
    778       </h2>
    779       <p id="rfc.section.B.1.p.1">Certain basic rules are in uppercase, such as SP, HTAB, CRLF, DIGIT, ALPHA, etc.</p>
    780       <div id="rfc.figure.u.27"></div> <pre class="inline">
     787      <div>
     788         <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;Acknowledgements
     789         </h1>
     790         <p id="rfc.section.A.p.1">The syntax for ABNF was originally specified in RFC 733. Ken L. Harrenstien, of SRI International, was responsible for re-coding
     791            the BNF into an Augmented BNF that makes the representation smaller and easier to understand.
     792         </p>
     793         <p id="rfc.section.A.p.2">This recent project began as a simple effort to cull out the portion of RFC 822 that has been repeatedly cited by non-email
     794            specification writers, namely the description of Augmented BNF. Rather than simply and blindly converting the existing text
     795            into a separate document, the working group chose to give careful consideration to the deficiencies, as well as benefits,
     796            of the existing specification and related specifications made available over the last 15 years, and therefore to pursue enhancement.
     797            This turned the project into something rather more ambitious than was first intended. Interestingly, the result is not massively
     798            different from that original, although decisions, such as removing the list notation, came as a surprise.
     799         </p>
     800         <p id="rfc.section.A.p.3">This "separated" version of the specification was part of the DRUMS working group, with significant contributions from Jerome
     801            Abela, Harald Alvestrand, Robert Elz, Roger Fajman, Aviva Garrett, Tom Harsch, Dan Kohn, Bill McQuillan, Keith Moore, Chris
     802            Newman, Pete Resnick, and Henning Schulzrinne.
     803         </p>
     804         <p id="rfc.section.A.p.4">Julian Reschke warrants a special thanks for converting the Draft Standard version to XML source form.</p>
     805      </div>
     806      <div id="CORE">
     807         <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a href="#CORE">Core ABNF of ABNF</a></h1>
     808         <p id="rfc.section.B.p.1">This appendix contains some basic rules that are in common use. Basic rules are in uppercase. Note that these rules are only
     809            valid for ABNF encoded in 7-bit ASCII or in characters sets that are a superset of 7-bit ASCII.
     810         </p>
     811         <div>
     812            <h2 id="rfc.section.B.1"><a href="#rfc.section.B.1">B.1</a>&nbsp;Core Rules
     813            </h2>
     814            <p id="rfc.section.B.1.p.1">Certain basic rules are in uppercase, such as SP, HTAB, CRLF, DIGIT, ALPHA, etc.</p>
     815            <div id="rfc.figure.u.27"></div><pre class="inline">
    781816      ALPHA          =  %x41-5A / %x61-7A   ; A-Z / a-z
    782817
     
    830865
    831866      WSP            =  SP / HTAB
    832                              ; white space </pre> <h2 id="rfc.section.B.2"><a href="#rfc.section.B.2">B.2</a>&nbsp;Common Encoding
    833       </h2>
    834       <p id="rfc.section.B.2.p.1">Externally, data are represented as "network virtual ASCII" (namely, 7-bit US-ASCII in an 8-bit field), with the high (8th)
    835          bit set to zero. A string of values is in "network byte order", in which the higher-valued bytes are represented on the left-hand
    836          side and are sent over the network first.
    837       </p>
    838       <h1><a id="rfc.copyright" href="#rfc.copyright">Full Copyright Statement</a></h1>
    839       <p>Copyright © The IETF Trust (2008).</p>
    840       <p>This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the
    841          authors retain all their rights.
    842       </p>
    843       <p>This document and the information contained herein are provided on an “AS IS” basis and THE CONTRIBUTOR, THE ORGANIZATION
    844          HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE
    845          DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN
    846          WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
    847       </p>
    848       <h1><a id="rfc.ipr" href="#rfc.ipr">Intellectual Property</a></h1>
    849       <p>The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might
    850          be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any
    851          license under such rights might or might not be available; nor does it represent that it has made any independent effort to
    852          identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and
    853          BCP 79.
    854       </p>
    855       <p>Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result
    856          of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users
    857          of this specification can be obtained from the IETF on-line IPR repository at <a href="http://www.ietf.org/ipr">http://www.ietf.org/ipr</a>.
    858       </p>
    859       <p>The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary
    860          rights that may cover technology that may be required to implement this standard. Please address the information to the IETF
    861          at <a href="mailto:ietf-ipr@ietf.org">ietf-ipr@ietf.org</a>.
    862       </p>
     867                             ; white space </pre></div>
     868         <div>
     869            <h2 id="rfc.section.B.2"><a href="#rfc.section.B.2">B.2</a>&nbsp;Common Encoding
     870            </h2>
     871            <p id="rfc.section.B.2.p.1">Externally, data are represented as "network virtual ASCII" (namely, 7-bit US-ASCII in an 8-bit field), with the high (8th)
     872               bit set to zero. A string of values is in "network byte order", in which the higher-valued bytes are represented on the left-hand
     873               side and are sent over the network first.
     874            </p>
     875         </div>
     876      </div>
     877      <div id="rfc.copyright">
     878         <h1><a href="#rfc.copyright">Full Copyright Statement</a></h1>
     879         <p>Copyright © The IETF Trust (2008).</p>
     880         <p>This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the
     881            authors retain all their rights.
     882         </p>
     883         <p>This document and the information contained herein are provided on an “AS IS” basis and THE CONTRIBUTOR, THE ORGANIZATION
     884            HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE
     885            DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN
     886            WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
     887         </p>
     888      </div>
     889      <div id="rfc.ipr">
     890         <h1><a href="#rfc.ipr">Intellectual Property</a></h1>
     891         <p>The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might
     892            be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any
     893            license under such rights might or might not be available; nor does it represent that it has made any independent effort to
     894            identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and
     895            BCP 79.
     896         </p>
     897         <p>Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result
     898            of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users
     899            of this specification can be obtained from the IETF on-line IPR repository at <a href="http://www.ietf.org/ipr">http://www.ietf.org/ipr</a>.
     900         </p>
     901         <p>The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary
     902            rights that may cover technology that may be required to implement this standard. Please address the information to the IETF
     903            at <a href="mailto:ietf-ipr@ietf.org">ietf-ipr@ietf.org</a>.
     904         </p>
     905      </div>
    863906   </body>
    864907</html>
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