The problem I mentioned before, though, is that XML Schema brings more issues to the table than it solves.
1) People inevitably use schema to generate bindings to [insert language], and because of the complexity of the underlying data model of XML (Infoset), the mapping of information items to objects can happen in a variety of different ways. This is an endless source of bugs. 2) It's very, very hard to define an XML Schema that's reasonably extensible; unless you use exactly the right design patterns in your schema (which are absurdly convoluted, btw), you'll end up locking out future backwards-compatible changes. The authority in this space is Dave Orchard; see his conclusions at <http://www.pacificspirit.com/Authoring/Compatibility/ProvidingCompatibleSchemaEvolution.html>. 3) An XML Schema can never express all of the constraints on the format. So, you'll still need to document those that aren't captured in the schema. I suppose the central question is what people are using the schema for. If it's just to document the format, that's great; we can have a discussion about how to do that. If they're using it for databinding, I'd suggest that JSON is far superior, as a separate databinding step isn't needed. Finally, if they're using it for runtime validation, I'd agree with Jay below; it's much easier to use json parse + runtime value checks for validation (especially in HTTP, where clients always have to be ready for errors anyway). Just my .02. Cheers, On 03/06/2011, at 5:20 AM, Jorge Williams wrote: > It's not just about the service itself validating it, its as Joseph said, > making sure that the data structures themselves are documented in detail to > the client. To my knowledge there is no accepted schema language in JSON > though JSON schema is starting to catch on. > > At the end of the day it should be a matter of providing our customers with a > representation that they can readily use. It could be that my perception is > wrong, but it seems to me that there's support for both representations. > I'll try to get some data to back this up. > > -jOrGe W. > > > On Jun 2, 2011, at 2:00 PM, Jay Pipes wrote: > >> On Thu, Jun 2, 2011 at 1:54 PM, Rick Clark <[email protected]> wrote: >>> Hi All, >>> Is it required for new openstack API's to support both JSON and XML, or >>> would it be acceptable to only support JSON? >> >> Glance currently does not support XML and I have no plans in the >> immediate future to add support for it. >> >> IMHO, JSON can be validated just as easily as XML. Simply >> json.loads(req.body) and then, if parsing succeeds, compare the >> mapping against a model. No need for XSDs, WADLs, or any other >> acronym. >> >> -jay > > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : [email protected] > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp -- Mark Nottingham http://www.mnot.net/ _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : [email protected] Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
