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    iSCSI: requirements terminology



    I've seen some confusion over use of words to
    express requirements in the iSCSI draft.  There
    are a couple of important points to keep in mind:
    
    (1) Unless there is some clear reason
    in the text of the iSCSI draft to interpret them in 
    some other fashion, "prohibited" is equivalent to
    "MUST NOT" and "mandatory" is equivalent to "MUST"
    (in their RFC 2119 meaning in both cases).  While RFC
    2119 terms provide clarity in requirement statements,
    the IETF does not require that all requirements be
    expressed using RFC 2119 terms, and it would certainly
    be wrong to interpret "prohibited" and "mandatory"
    as not stating requirements solely because 
    those two terms are not defined in RFC 2119.
    
    (2) OTOH, use of an RFC 2119-defined term in lower
    case (e.g., "must", "should") assigns the common usage
    (i.e., dictionary) meaning to that term rather than
    its RFC 2119 meaning.  Such a term may still express
    a requirement, but that depends on the specific
    usage and context.  It is also the case that the common
    usage meaning of "should" is weaker than the RFC 2119
    meaning of "SHOULD" (and similarly for "should not" vs.
    "SHOULD NOT").  It is generally reasonable to initially
    assume that use of a lower case version of an RFC 2119
    term was a deliberate decision made by the draft
    author(s) and/or the WG to limit usage of RFC 2119 terms
    in accordance with the guidance in Section 6 of RFC 2119,
    but this needs to be checked based on the actual usage
    and context in each case.
    
    Thanks,
    --David
    
    ----------------------------------------------------
    David L. Black, Senior Technologist
    EMC Corporation, 176 South St., Hopkinton, MA  01748
    +1 (508) 293-7953 **NEW**     FAX: +1 (508) 293-7786
    black_david@emc.com        Mobile: +1 (978) 394-7754
    ----------------------------------------------------
    


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Last updated: Mon Nov 11 11:19:10 2002
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