I strongly disagree that XSD (RelaxNG or any other way of specifying the structure of the XML messages) is a "waste of time". If you don't have a schema, you'll either end up implementing all the validation manually or worse crash on invalid input. XSD parser-validators (they exist) do all that work for you, and are optimized to do that.
Without a schema, all we have is the text and examples which could be interpreted in many ways by how they are written and how they are understood by the reader. Requiring a schema also forces the XEP authors to think hard and come up with a design that's structured, extensible (Yes, XSD schemas can be made extensible). -- Bala -----Original Message----- From: standards-boun...@xmpp.org [mailto:standards-boun...@xmpp.org] On Behalf Of Hannes Tschofenig Sent: Friday, December 09, 2011 12:36 PM To: XMPP Standards Subject: Re: [Standards] Schemas in XEPs Hi Dave, Over the time I have gotten the impression that an XML schema is really a waste of time. It creates the illusion that there is something that provides help (to implementers and to those who read the specification) but in reality it doesn't. Working on different specifications I later thought that the problem is with the readability and extensibility of the XML schema and then we switched to Relax NG in some IETF working groups. That turned to be a mistake as well. When it comes to extensibility a Relax NG schema is equally bad. The extensibility mechanism of XML would prevent you from getting any meaningful validation anyway. So, validation isn't useful because more or less everything validates (after you add the extension points everywhere). So, I believe we are doing fine without XML schema but with lots of examples. Implementers just look at examples. Maybe you could therefore recommend not to use XML schemas (or Relax NG schemas). Ciao Hannes On Dec 9, 2011, at 6:24 PM, Dave Cridland wrote: > On Thu Dec 8 23:13:38 2011, Matthew A. Miller wrote: >> I'd like to point out that all of our XML Schemas are non-normative. >> They're provided for informational use, and ought not be considered the >> absolute record of authority. > > What follows is my understanding; we should probably have this documented > somewhere (a Tao Of XSF XEP?): > > - The schemas in XEPs are not normative. > - We do, however, try to keep them aligned properly with the text, and will > accept bug reports with gratitude. > - The schemas in RFCs *are* normative. > - The IETF does, however, accept errata should they not match the text or the > intent. > > So in both cases, we'd expect the schemas to be right, and welcome fixes; > technically, though, there's a distinction in normativeness (normativity?) > between RFC and XEP. > > Dave. > -- > Dave Cridland - mailto:d...@cridland.net - xmpp:d...@dave.cridland.net > - acap://acap.dave.cridland.net/byowner/user/dwd/bookmarks/ > - http://dave.cridland.net/ > Infotrope Polymer - ACAP, IMAP, ESMTP, and Lemonade
