Re: [apps-discuss] JSON Schema considered harmful
Erik Wilde <dret@berkeley.edu> Thu, 20 September 2012 16:26 UTC
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Subject: Re: [apps-discuss] JSON Schema considered harmful
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hello all. On 2012-09-20 09:02 , Nico Williams wrote: > So, while I have no problem with specific complaints about > shortcomings of one or another schema language, I do object to the > idea that because they fail to denote semantics we should not use > them. that's my general feeling as well. schemas are not able to and not designed to completely capture protocol semantics, but they provide a good starting point, and allow some level of formalism which then needs to be augmented with documentation. > Regarding specific complaints... I am not very familiar with XML > Schema, so I can't say much about it and extensibility. ASN.1 has > extensibility rules nowadays, and often uses of ASN.1 predating > extensibility rules are nonetheless extensibile (sometimes we need to > resort to negotiation of extensions, but that's OK). I suspect that > the situation w.r.t. XML Schema extensibility is not as dire as you > paint it. imho, the real challenge is to *design* a good extension model for a language; coding it in a schema language then is just an exercise in figuring out what can be done in that specific language. in XSD, all you can do is to use wildcards (possibly refined by namespace specifications for them), and then you have to add documentation saying how processors are supposed to handle wildcards (ignore, interpret, stop, ...). extension rules cannot be fully captured (such as saying that extensions are not allowed to change the semantics of any fields in the base format), but at least the schema describes the base syntax, and also validates instances containing extensions. i have to admit that i am really curious why the seasoned spec writers that have voiced general concerns about the usefulness of schema languages are feeling this way, but so far i have not really understood what they are saying. could somebody please try again, i'd really like to understand why the general idea of describing protocol syntax in a semi-formal (as opposed to non-formal) way is considered a bad idea. thanks a lot and kind regards, dret. -- erik wilde | mailto:dret@berkeley.edu - tel:+1-510-2061079 | | UC Berkeley - School of Information (ISchool) | | http://dret.net/netdret http://twitter.com/dret |
- [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Nico Williams
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Nico Williams
- Re: [apps-discuss] JSON Schema considered harmful James M Snell
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Tschofenig, Hannes (NSN - FI/Espoo)
- Re: [apps-discuss] JSON Schema considered harmful Nico Williams
- Re: [apps-discuss] JSON Schema considered harmful Erik Wilde
- Re: [apps-discuss] JSON Schema considered harmful Nico Williams
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Erik Wilde
- Re: [apps-discuss] JSON Schema considered harmful Tim Bray
- Re: [apps-discuss] JSON Schema considered harmful Bob Wyman
- Re: [apps-discuss] JSON Schema considered harmful James M Snell
- Re: [apps-discuss] JSON Schema considered harmful evan@status.net
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Julian Reschke
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful Julian Reschke
- Re: [apps-discuss] JSON Schema considered harmful Mark Nottingham
- Re: [apps-discuss] JSON Schema considered harmful Dave Crocker
- Re: [apps-discuss] JSON Schema considered harmful Tim Bray
- Re: [apps-discuss] JSON Schema considered harmful Dave Crocker
- Re: [apps-discuss] JSON Schema considered harmful Phillip Hallam-Baker
- Re: [apps-discuss] JSON Schema considered harmful SM
- Re: [apps-discuss] JSON Schema considered harmful Francis Galiegue
- Re: [apps-discuss] JSON Schema considered harmful Martin J. Dürst
- Re: [apps-discuss] JSON Schema considered harmful Hannes Tschofenig
- Re: [apps-discuss] JSON Schema considered harmful Andrew Newton
- Re: [apps-discuss] JSON Schema considered harmful Dave Crocker