Authoring Schemas With XSD

Dare Obasanjo points to his own "article on O'Reilly's XML.com that specifies a set of guidlelines for authoring schemas using the W3C XML Schema Definition language commonly abbreviated as XSD. The primary theme is embracing simplicity by showing how to avoid the more complex and esoteric features of the language."

Comments

Just Say NO!

[gurnb]

James Clark fights with XSD, pushing his Relax NG. Relax NG is *not* W3C. Let me repeat a background.
XML (markup language created by W3C) is a subset of SGML (markup language created by ISO).
XML has been created by few smart marginals from SGML world plus some MS politicians
Now those MS politicians (and alikes) rule the show in W3C and the smart marginals have left W3C and work for ISO ( OASIS ).
XSD is XML Schema language by W3C. Relax NG is XML Schema language by ISO (OASIS). Sofar, Relax NG is the first visible XML applicatuon which belongs not to W3C
Now when we have a big picture written down, I would recommend reading the letter from James Clark
http://www.imc.org/ietf-xml-use/mail-archive/msg 00 217.html
The RELAX NG formalism has a solid basis in tree automata theory. W3C XML Schema has no such basis.

e t.c.
BTW, even RELAX NG is definately better than XSD, Relax NG itself is also not that perfect. The 'perfect' solution could be based on regular expressions. Nevermind. In the next years, nothing interesting (except for political battles) would happen in the world of XML Schema.

Among other things, XML is used for APIs

[Anonymous Coward]

The product I work on (billing software) uses XML to define the API we export for external systems. A client that wants functionality not provided by our stock system is free to develop its own programs (front end and back end) that uses our XML interface to get the data.

A client will call an API such as getFOO which will have an input type of InputGetFoo and an output type of OutputGetFoo defined in an xsd file. Because both our system and the client use the same xsd files, there is very little problem with synchronization. Using xml allows our clients to have a heterogenuous environment; anything that can deliever xml over tcp/ip can use our interface.

Re:So the XML Definition language is itself XML?

[J. Random Software]

They wrote a schema as well as a DTD (which has the usual namespace validity problems). XSD may be big and ugly, but the designers would have noticed if it couldn't even describe itself.

If it actually takes months to understand

[msobkow]

Then maybe you just shouldn't be doing such "complex" programming. XSD should not take more than a couple days to understand, another few days to iron out the details, and by the end of 30-40 hours you should have produced a good sample of whatever you're modelling with XSD.

Too many "how to" documents and books are written for people who just don't "get it". While I sympathise that they need to learn, you have to grasp the concept of abstraction before some of these "languages" make sense. XSD, ERDs, SQL-DDL, etc. are just different ways of describing data structures and organization. Each is "complex" if you try to make it do more than it was intended for, but only takes a couple weeks to understand well enough to get by.

Re:Darn DTD's

[Theatetus]

I don't think people should be able to just make up their own standards.

Isn't that the whole point of XML to begin with? That my company and the company we're partnering with can write a simple data-exchange standard without locking both development teams in a conference room for two weeks?

So, in your case, you and whoever your dealing with could pretty easily nail down what kind of namespace smarts you want in your DTD validations and implement it without having to RFC the whole world.