[rfc-i] Deprecated pieces and PIs [was: Re: Input Syntax vs Canonical Form/rfcedstyle vs Output Formats]

Elwyn Davies elwynd at folly.org.uk
Fri May 2 09:08:06 PDT 2014

On Fri, 2014-05-02 at 07:57 -0500, Dave Crocker wrote:

> pps.  The long list of deprecated features is distressing.  Given the
> earlier discussions, it never occurred to me that there would be so
> little concern for staying compatible with the installed base.  But
> then, the IETF seems to have largely lost its appreciation for the role
> of operational stability...
As I understand the specification, the pieces that are labeled as
'deprecated' MUST be implemented in v3 processors and the syntax and
semantics will be as defined in the v2 specification.  Consequently
existing v1 and v2 documents ought to be able to be processed by a v3
processor (see para 6 of s1.1).  This seems to have an adequate eye to
operational stability; unfortunately I think the eye was slightly

Boringly, achieving full backwards compatibility will mean the v3
processor has to implement the old v1/v2 processing instructions that
have been deprecated or moved into the grammar in v3.  

This means that Appendix B.4 is not right.  It effectively says that
only 3 PIs need to be implemented in a v3 processor and the v1/v2 PIs
can be eliminated.

I think a note about the changes to PIs ought to be added to s1.2.3 or


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