- From: C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
- Date: Thu, 16 Dec 2021 10:59:57 -0700
- To: Dave Pawson <dave.pawson@gmail.com>
- Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, Norm Tovey-Walsh <norm@saxonica.com>, ixml <public-ixml@w3.org>
> On 16,Dec2021, at 10:31 AM, Dave Pawson <dave.pawson@gmail.com> wrote: > ... >> >> That is why I say that []? is a way of writing the empty sequence. >> It recognizes a set of input sequences that contains the empty >> sequence and no other sequences. > > How to avoid having this discussion a thousand times over in the future? > Is it feasible to extract 'implementer' notes (with this inclusion) and > a simpler (glossed) term for users? Perhaps 'glossed over' more accurately. > Estimate: For each MSM there are 10^n DP's | those not exposed to set theory. > <grin/> Good question: I think maybe - use empty comments ourselves, in our examples and (as Norm suggested) in the rewritings shown in the implementor hints - comment that we do so in order to make it easier to see that there is an alternative which contains nothing and matches the empty sequence That should cover people who wonder how to write an expression which matches the empty sequence. Very few people are conscious of wanting to write an expression whose language is the empty set, so I don’t think we need to explain in the spec how to do that. If I’m right, they will all be people with automata theory on their minds, and those people should have little trouble picking up on the fact that [] is such an expression. Michael
Received on Thursday, 16 December 2021 18:00:18 UTC