[OASIS Issue Tracker] (MQTT-145) MAY/may contain inconsistent usage - 1 known, others need researching

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://tools.oasis-open.org/issues/browse/MQTT-145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=36899#comment-36899 ] 

Richard Coppen commented on MQTT-145:
-------------------------------------

TC accept proposal, TC call 20.03.2013

> MAY/may contain inconsistent usage - 1 known, others need researching
> ---------------------------------------------------------------------
>
>                 Key: MQTT-145
>                 URL: https://tools.oasis-open.org/issues/browse/MQTT-145
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.1.1
>         Environment: Keywords
>            Reporter: Patrick Durusau
>
> Section 3.8.3 Payload reads in part:
> *****
> The Topic Filters are UTF-8 encoded strings, which *MAY* contain special wildcard characters to represent a set of topics, see Section 4.7.1.
> *****
> Whereas 4.7.1 reads:
> *****
> A subscription's Topic Filter *may* contain special wildcard characters, which allow you to subscribe to multiple topics at once.
> *****
> The difference between "MAY" and "may" for interoperability is substantial:
> Under RFC2119, MAY is defined as:
> *****
> MAY   This word, or the adjective "OPTIONAL", mean that an item is truly optional.  One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.)
> *****
> So the first "MAY" has an interoperability requirement between applications that support or don't support the use of wildcards to select sets of topics. 
> However, that interoperability requirement is *lost* in 4.7.1, which uses the lowercase "may," according to The RFC Style Guide, http://www.rfc-editor.org/rfc-style-guide/rfc-style, which reads in part:
> *****
> To simply specify a necessary logical relationship, the normal lower-case words should be used.  On the other hand, if the capitalized words are used in a document, choose and use them carefully and consistently.
> *****
> The short version: MAY requires interoperability, may does not require interoperability.
> I mention this because the specification uses MAY 21 times and may 39 times. I suggest that you carefully compare all uses of MAY/may to eliminate further conflicts like this one.  



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