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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (May 2012) is 4362 days in the past. Is this intentional? Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Hansen 3 Internet-Draft AT&T Laboratories 4 Intended status: Best Current Practice D. Crocker 5 Expires: October 31, 2012 Brandenburg InternetWorking 6 May 2012 8 Non-Normative Synonyms in RFCs 9 draft-hansen-nonkeywords-non2119-02 11 Abstract 13 Specifications in RFCs contain normative keywords, as defined in RFC 14 2119, to signify requirements, permission or prohibitions. These 15 include MUST, SHOULD and MAY, which are commonly recorded in all 16 CAPITALS (but need not be). The words are sometimes also intended 17 with non-normative meaning; this different usage can be confusing. 18 Happily there are adequate alternatives for non-normative meanings. 19 For such situations, this document provides some alternatives to the 20 normative vocabulary of RFC 2119. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on October 31, 2012. 39 Copyright Notice 41 Copyright (c) 2012 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents (http://trustee.ietf.org/ 46 license-info) in effect on the date of publication of this document. 47 Please review these documents carefully, as they describe your rights 48 and restrictions with respect to this document. Code Components 49 extracted from this document must include Simplified BSD License text 50 as described in Section 4.e of the Trust Legal Provisions and are 51 provided without warranty as described in the Simplified BSD License. 53 1. A List of Synonyms 54 To indicate a degree of requirement, permission or prohibition for an 55 aspect of a specification, words such as MUST, SHOULD and MAY are 56 defined as normative vocabulary in the formal aspects of the RFC 57 series.[RFC2119]. However it is also natural to use them non- 58 normatively, in a narrative fashion. Even when this is permitted, 59 such as RFCs that do not invoke the conventions of RFC 2119, non- 60 normative use of these words is often confusing; their normative 61 meaning is too deeply ingrained in the culture of the RFC series. 63 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 64 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 65 document are to be interpreted as described in [RFC2119]. 67 Fortunately, there are other words readily available, in lieu of the 68 RFC 2119 words. These alternatives, or their equivalents, SHOULD be 69 used instead of their normatively-encumbered vocabulary. 71 MUST, REQUIRED, SHALL: The words "needs to" and "necessary" SHOULD 72 be used to connote that something is essential. 74 SHOULD, RECOMMENDED: The words "ought", "encouraged" and "suggest 75 strongly" SHOULD be used to connote that something is strongly 76 urged. 78 MAY, OPTIONAL: The words "can" and "might" SHOULD be used to 79 indicate the possibility or capability of performing an action. 80 The words "is allowed to" or "is permitted to" SHOULD be used 81 to indicate permission to perform an action. 83 NOT: The word "not" can be freely used with any of the above 84 suggestions and will not be taken to have any separate RFC 2119 85 connotation. The word only takes on a special meaning when it 86 is combined with one of the RFC 2119 normative words. For 87 example, "ought not" is non-normative, while "should not" and 88 "SHOULD NOT" are normative in the RFC 2119 sense. 90 RFCs that cite RFC2119 vocabulary usage MUST NOT employ the listed, 91 normative vocabulary for non-normative meaning. RFCs that do not 92 cite RFC2119 SHOULD NOT employ that vocabulary. 94 Note that the above list of synonyms is not meant to be exhaustive; 95 other non-RFC2119-normative words MAY also be used at the author's 96 discretion. 98 Authors who follow these guidelines MAY incorporate a declaration at 99 the beginning of their document, but note that this is not required. 101 This document can be discussed on the ietf@ietf.org mailing list. 103 2. Acknowledgements 104 Ran Atkinson 106 3. IANA Considerations 108 This document has no IANA considerations. 110 4. Security Considerations 112 The 2119 terms are frequently used to specify behavior with security 113 implications. The effects on security of changing something from a 114 "MUST" to a "needs to", or vice versa, can be very subtle, as one has 115 normative meaning and the other does not. Document authors need to 116 take the time to consider the effects of using non-normative verbiage 117 as specified in this document instead of the normative verbiage from 118 2119. 120 5. References 122 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 123 Requirement Levels", BCP 14, RFC 2119, March 1997. 125 Authors' Addresses 127 Tony Hansen 128 AT&T Laboratories 129 200 Laurel Ave South 130 Middletown, NJ 07748 131 USA 133 Phone: +1.732.420.8934 134 Email: tony+nonkeywords@maillennium.att.com 136 D. Crocker 137 Brandenburg InternetWorking 138 675 Spruce Dr. 139 Sunnyvale, 140 USA 142 Phone: +1.408.246.8253 143 Email: dcrocker@bbiw.net 144 URI: http://bbiw.net