Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!usc!snorkelwacker!bloom-beacon!eru!luth!sunic!mcsun!unido!wrkof!smurf!urlichs From: urlichs@smurf.sub.org (Matthias Urlichs) Newsgroups: comp.mail.uucp Subject: Re: Paths and Precedence (Re: Question about From: lines) Message-ID: Date: 6 Jul 90 22:05:25 GMT References: <696@logicon.com> Organization: University of Karlsruhe, FRG Lines: 36 In comp.mail.uucp, article , fitz@wang.com (Tom Fitzgerald) writes: < Makey@Logicon.COM (Jeff Makey) writes: < > [ RFC1123 example ] < > The use of parentheses in the example is a poor attempt at using < > algebraic notation to describe source routing, but the part about < > "lower precedence" indicates to me that "a!b%c" means "deliver to "a", < > who should interpret "b%c" as a local-part. This is the One True < > Order of Precedence. < < That's exactly the opposite of how I read it. The words "higher precedence" < and "lower precedence" apparently mean different things to different people, < and I won't use them. The RFC seems to be saying that ! binds tighter < than %, whence the interpretation of a!b%c as (a!b)%c. This implies < immediate delivery to c, which is solely responsible for interpreting a!b < however it wishes. < Using parentheses, as well as talking about "binding tighter" or "precedence", is highly ambiguous in this context. Does a!(b%c) mean that b%c is to be evaluated first (as in mathematics), resulting in c!a!b, or that b%c is to be seen as one unit (as in a graph), making the message go a!c!b? < I agree with you that interpreting a!b%c as a!(b%c) would be better. < I assume you mean a!c!b here. ;-) Whatever RFC1123 says, and/or whatever we think it says, it seems that visualizing a!b%c as a!c!b (without actually rewriting it that way, and especially without rerouting it to what you think "c" is supposed to be) is the right way to do it, with "right" being defined as breaking less things than doing it the other way 'round. Unfortunately, many vendor-supplied sendmail.cf's do not share this opinion. -- Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(Voice)/621227(PEP)