Eric Rescorla wrote:
Perhaps the RFC Editor Style Manual
offer some insight here:
At Mon, 11 Feb 2008 19:16:57 -0000,
Adrian Farrel wrote:
An interesting fact is that the RFC Editor process is particularly hot on
"that"/"which". This may be a function of the use of copyeditor function
since these folk tend to care about English usage and for them (and for me)
it *is* much more than "neither here nor there". It could even have an
impact on meaning in an RFC.
In converting what is now RFC 1716 to RFC 1812, which was a HUGE
editing task, I used a brand new tool that is now a popular grammar
checker. It complained about "which" vs "that", which is neither here
Well, not quite. "That" is for defining relative clauses, and "which"
for non-defining relative clauses.
This kind of grammar theead usually ends in tears.
That said, the CMS is pretty wishy-washy on this:
A distinction has traditionally been made between the relative
pronouns which and that, the latter having been long regarded
as introducing a restrictive clause and the former, a nonrestrictive
one. Although the distinction is often disregarded in contemporary
writing, the careful writer and editor should bear in mind that such
indifference may result in misreading or uncertainty, as in the
The report which Marshall had tried to suppress was greeted with
Which of the following is meant:
The report, which Marshall had tried to suppress, was greated
The report that Marshally had tried to suppress was greeted
When the commas intended to set off a nonrestrictive lcause are
ommitted, perhaps with the purpose of using which restrictively,
the reader may well wonder whether the omission was inadvertant.
Some uncertainty will persist.
The MLA handbook is even less prescriptive:
"Note that some writers prefer to use which to introduce
norestrictive clauses and that to introduce restrictive
Given that the distinction between which and that is not
universally observed and that our documents are intended
to be consumed in part by those who are not native
English speakers, ISTM that any case where the distinction
between which and that is important to meaning would benefit
from some rephrasing for increased clarity.
* "which" and "that" should follow the rules:
o "which" is non-restrictive and is used parenthetically. It
follows a comma and provides non-essential information.
"The XYZ Protocol, which is proprietary, may be vulnerable
to session hijacking"
o "that" is restrictive and introduces information that is
essential to the meaning of the sentence. Example:
"A protocol that is less robust may be more vulnerable to
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