Re: [xml2rfc] assuming that period (.) ends a sentence is sometimes wrong

Carsten Bormann <> Sat, 27 February 2021 19:57 UTC

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From: Carsten Bormann <>
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Date: Sat, 27 Feb 2021 20:57:20 +0100
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Subject: Re: [xml2rfc] assuming that period (.) ends a sentence is sometimes wrong
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On 2021-02-27, at 20:16, John Levine <> wrote:
> I don't know why it went into 7322 or who removed it in the draft or why.
> Personally, I'm with you.  The extra space is an antique tradition from
> the days of manual typewriters and I don't see any reason to worry about it
> any more.  

That statement is often repeated, but sentence spacing actually has nothing to do with typewriters (except that there needed to be a way to emulate it with typewriters, which is the reason that it is often reduced to “single space vs. double space” — not the choice we have today).  This confusion may have influenced the discussion, as the perception indeed is that sentence spacing is a remnant from typewriter days, when it simply was good typography for centuries (actually often applying a number of different spacing regimes after semicolons, colons, and periods).

I think we also have data that may warrant a discussion about the implications of the direction fashion has taken here.

Even Forbes [1] (whose take on science warrants, er, discussion) did not manage to totally dismiss the results of a study that showed the benefits for legibility of extended spaces after sentence ends.


As I hinted, the fashion is moving away from this legibility aid [2].
Anecdotically I can say that my reading speed and comprehension benefits mightily if document authors have taken the care to insert wider sentence ends, so for me this is simply a loss of quality.


> If you care about legibility, read the HTML version with those
> nice proportional typefaces.

Somewhat ironically, “proportional” (i.e., non-monospaced) typefaces benefit way more from wide sentence end spaces than monospaced ones.  In the latter, the wide period is already adding some visual spacing, which is lost with the thin periods in non-monospaced type.  

Typesetting systems have of course supported sentence spacing since the 1970, and, e.g., troff hat different settings for spaces between words and spaces placed  at a sentence end (.ss setting, first and second parameter; in serious typesetting it was customary to set the first to 1/3 em and the second to 1/2 em, i.e. 1.5 times the inter-word spacing).  But DTP may have put an end to this great period.

For mass-market tools like MS-Word, the legibility feature of sentence spacing may simply take too much effort, and we may want to decide the same for RFC production.  But that doesn’t make it the right decision.

Grüße, Carsten