Re: [YANG] so many naming scopes

----- Original Message -----
From: "Phil Shafer" <phil@juniper.net>
To: "tom.petch" <cfinss@dial.pipex.com>
Cc: "Bert Wijnen - IETF" <bertietf@bwijnen.net>et>; "Andy Bierman"
<ietf@andybierman.com>om>; <yang@ietf.org>
Sent: Tuesday, January 08, 2008 11:30 PM
Subject: Re: [YANG] so many naming scopes

> "tom.petch" writes:
> >There are languages where no word is reserved, where the same symbol(word)
can
> >be used for label, type, module etc.  XML is arguable worse with the ability
to
> >start a fresh namespace on alternate lines.  These belong in the bin.
>
> That's a very strong statement, given that the motivation for
> avoiding reserved words is typically future proofing.  Don't paint
> it as a universally bad feature.
>
> For example, if I use "action" as a leaf in my model and the next
> version of YANG adds a feature that uses "action" as a keyword, my
> model is broken and needs repair.
>
> Many languages reserve unused keywords just on the odds they will
> need them in the future, but they are seldom right.  By keeping the
> namespace of user-defined stuff out of the namespace of keywords,
> YANG avoids this issue entirely.  As the number of modules defined
> in YANG approaches the number that are defined in SMI, this will be
> an important language feature.
>
Yes, I expressed myself strongly, perhaps as a result of spending time in 2007
with XML documents where there was widespread use of an element named <element>
as well as one named <attribute>; I wish that XML had reserved those words:-(  I
accept that it is a trade off, and devising a language without reserved words is
an achievement; but I find it costs usability when eg you can have labels such
as 'if' and 'then' and variables such as 'for' and 'case'.  I mean, it is sort
of obvious, you are writing this small simple program that will only ever have
one case construct so it is natural to name the associated variable 'case'.

If a language has concepts which are widely written about in English - perhaps
container, leaf, index, key would qualify - then I would prefer those to be
reserved, else someone someday will use them.

Tom Petch

> Thanks,
>  Phil

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