Covered exactly what is needed
I tried learning RELAX NG by looking at a few HOWTOs, but there was clearly a lot more to it than what they presented. This book is clear, detailed, and the verbose examples are very helpful.
The rule of XML schema
Years ago I attended an ASP Professional Developers conference in Washington, DC, and one of the most inspiring lectures was by a Microsoft XML evangelizer who claimed "It's all about the schema". He might have been right, but on practical level, the transition between XML 1.0 DTDs and W3C XML Schema has been neither easy nor intuitive.The emergence of RELAX NG is a testimony of the power of the open source movement. While admitting the need for standards (and recommendations) it was obvious that the powerful XML Schema would benefit from the ease of DTDs. RELAX NG is the answer to that need.
The book by the same name by Eric van der Vlist provides not only a description of what RELAX NG is and where it fits in the XML universe, but also guides you through a list of techniques, best practices and integration ideas.
For those among us who are not XML gurus, a book like this can be eye-opening because let's face it, you do not hear about RELAX NG outside of the XML community.
O'Reilly has been very good about publishing thorough books on emerging topics and this book is not an exception. It manages to inform yet not overwhelm. What more can you expect from a computer book?
Short but thorough
This is a solid work on Relax NG. The text is very thorough and the author obviously knows what he is talking about. On it's face that makes this a must have book for NG users.It's not without it's flaws however. The graphics are poor and there could be more done to impart how the Relax NG specifications relate to the specific XML examples they are validating. In addition the book provides little information about tools and support for NG, and also neglects to relate NG to any of the other XML validation standards (DTD, XML Schema.)
For a book about a tough subject it does a lot in a small space. For someone looking for information about NG who is going to apply it in the near term this is a fine work.
Relax NG is facing an uphill road
By now, XML is entrenched as the most common and flexible standard for data interchange. There is no real dispute over this. But in the quick uptake of XML, the DTDs rapidly showed their shortcomings. So a more expressive schematic standard was hurriedly put together, under the generic name of XML Schema.But, as van der List points out, some users took issue with the complexity and verbosity of XML Schema. An alternative emerged, Relax NG, which is described in detail here. The author's assessment that Relax is in fact cleaner and simpler to use than XML Schema seems correct. I cannot find technical flaws in his argument.
There are two problems, though. XML Schema has greater acceptance. Certainly aided by the very generic and definitive nature of its name. While this may not be quantifiable, it certainly does not help Relax. For example, think of "Microsoft Windows". In common parlance, this is elided to "Windows". So if you say the latter, in referring to any computer GUI, some might assume you mean the Microsoft version. Very aggravating! There is some of this going on here.
The other problem is that both approaches have essentially the same functionality. While there may be some things you can do in Relax that are not possible in the other, this may not be enough. Ditto for the simpler syntax of Relax.
Remember IBM's OS/2 versus Microsoft Windows? Most observers with no pony in that race gave an overall technical advantage to OS/2. But it was driven to extinction. A similar fate might befall Relax.
(4 reviews)
