norman.walsh.name: Comments on /2004/01/12/postelhttp://norman.walsh.name/2004/01/12/postel/comments.atom2012-02-13T04:21:07.132858ZComment 1 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00012004-01-13T13:03:05Z2004-01-13T13:03:05ZTobi

I strongly agree.

Comment 2 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00022004-01-13T13:34:20Z2004-01-13T13:34:20ZEd Daviesda39a3ee5e6b4b0d3255bfef95601890afd80709

There are two interpretations of Postel's Law: the conservative and the liberal. The conservative interpretation is that if there is an ambiguity in a specification then you should:

1. Be careful not to produce data whose compliance is ambiguous.

2. Be careful to accept any data which might reasonably be considered to comply with the specification.

Also, maybe you should fix the specification.

The liberal interpretation of Postel's Law is that even data streams which unambiguously do not comply with the specification should be accepted.

I'm fully in favour of the conservative interpretation but I think anybody who supports the liberal interpretation rather misses the point of having a specification in the first place.

Comment 3 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00032004-01-14T03:51:24Z2004-01-14T03:51:24ZNorman Walshda39a3ee5e6b4b0d3255bfef95601890afd80709

Good point, Ed!

Comment 4 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00042004-01-14T06:08:19Z2004-01-14T06:08:19ZMark Pilgrimda39a3ee5e6b4b0d3255bfef95601890afd80709

This page is not valid XHTML ( http://validator.w3.org/check?uri=http://norman.walsh.name/2004/01/12/postel ). Luckily for you, my browser is very forgiving, and displayed your little rant as best it could. And thank goodness for that, otherwise we would not be able to have this stimulating conversation!

Comment 5 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00052004-01-14T06:18:37Z2004-01-14T06:18:37ZMark Pilgrimda39a3ee5e6b4b0d3255bfef95601890afd80709

It is probably worth noting at this point that Tim Bray just called you a bozo and an incompetent fool. http://www.tbray.org/ongoing/When/200x/2004/01/11/PostelPilgrim

Comment 6 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00062004-01-14T15:58:06Z2004-01-14T15:58:06ZDanny Ayersda39a3ee5e6b4b0d3255bfef95601890afd80709

I've a feeling that XML isn't actually an *exception* to Postel's law, because XML isn't designed to be robust at this level. The 'law' simply doesn't apply. Try applying Postel to RDBMS clients.

Comment 7 on /2004/01/12/postelhttp://norman.walsh.name/2010/09/25/oauth#comment00072004-03-16T13:49:13Z2004-03-16T13:49:13ZJim Dabellda39a3ee5e6b4b0d3255bfef95601890afd80709

I think Postel's Law needs an addendenum: be liberal in what you accept *unless you have reason to believe the other side (be conservative in what you send) will not hold up their end of the bargain*.

It's abundantly clear from HTML's history that unless there is pressure to author well-formed markup, then a vast number of people simply won't make any attempt to "be conservative in what they send". Without this attempt, Postel's Law falls to pieces and developers get caught in an error-handling arms race.

Mark, I've noticed you are in the habit of pointing out when an XHTML page is invalid. You are supporting my point by doing so - when served as text/html, there is *no pressure* to send well-formed XHTML, and people simply don't put any effort into doing so. If you were pointing out malformed XHTML when it will actually be treated as XML you would be supporting your point.

Also, pointing out that an XHTML document is invalid is of no consequence - you should be pointing out when an XHTML document is malformed, since the issue is whether XML documents are well-formed or not, not whether they are valid or not.