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Tim Bray Says RELAX
twofish writes to tell us that Sun's Tim Bray (co-editor of XML and the XML namespace specifications) has posted a blog entry suggesting RELAX NG be used instead of the W3C XML Schema. From the blog: "W3C XML Schemas (XSD) suck. They are hard to read, hard to write, hard to understand, have interoperability problems, and are unable to describe lots of things you want to do all the time in XML. Schemas based on Relax NG, also known as ISO Standard 19757, are easy to write, easy to read, are backed by a rigorous formalism for interoperability, and can describe immensely more different XML constructs."
When you want to come.
On the other hand, RELAX NG "just works".
(all IME of course...:)
ant.
Has anyone here ever tried to read an XML schema for anything relatively complex? It's a nightmare. RELAX looks much cleaner and more direct, which I wholeheartedly approve of.
using namespace slashdot;
troll::post();
"W3C XML Schemas (XSD) suck"
Hey Tim, don't hold back, tell us what you really think.
xml is a b**ch to read
Don't forget what we used to use... binary is even worse. XML was designed with people in mind, which is why it's easier for people to read and manipulate than your traditional binary file format.
Helpful hint for understanding the above: Tim Bray, author of TFA, is one of the guys who originally developed and spec'd out XML. Really. His name's on the spec and everything. So if he says that a particular XML tool has problems, it's probably a good idea to take him at his word ;)
And if you can't have a DB connection?
:(
For flat data, sure a flat file is fine...for structured/hierarchical data, a flat file is
I refuse to use XML in any shape way or form no matter what anyone say or does with it!!!
Check out YAML.
XML would be great if people validated their XML files before sending them out. And cut the verbosity and redundancy down by 90%. And used english elements instead of numbers. Ahh XML, the ideal most people pay lip service to but up to which they fail to live.
Relax NG has a compact non-XML syntax. But C++/Java is a horrible syntax to use if you want a language to be readable and easy to understand. Since when was 17 levels of operator precedence easy to understand? Of course any good programmer always uses parenthesis to avoid ambiguity, so why should a language have 17 levels of built-in ambiguity just to make it that much easier to make hard to find mistakes?
-Don
From my blog: Relax NG Compact Syntax: no to operator precedence, yes to annotations!
James Clark is a fucking genius! Hes the guy who wrote the Expat XML parser, works on Relax NG, and does tons of other important stuff. Relax NG is an ingeniously designed, elegant XML schema language based on regular expressions, which also has a compact, convenient non-xml syntax.
I totally respect the way he throws down the gauntlet on operator precedence (take that you Perl and C++ weenies!):
You can translate back and forth between Relax NG's XML and compact syntaxes with full fidelity, without losing any important information. Relax NG supports annotating the grammar with standard and custom namespaces, so you can add standard extensions and extra user defined meta-data to the grammar. That's useful for many applications like user interface generators, programming tools, editors, compilers, data binding, serialization, documentation, etc.
Here's an interesting example of a complex Relax NG application: OpenLaszlo is an XML/JavaScript based programming language, which the Laszlo compiler translates into SWF files for the Flash player. The Laszlo compiler and programming tools use this lzx.rnc Relax NG schema for the OpenLaszlo XML language. This schema contains annotations used by the Laslzo compiler to define the syntax and semantics of the XML based programming language.
The schema starts out by defining a few namespaces:
default namespace = "http://www.laszlosystems.com/2003/05/lzx" .0"
namespace rng = "http://relaxng.org/ns/structure/1.0"
namespace a = "http://relaxng.org/ns/compatibility/annotations/1
datatypes xsd = "http://www.w3.org/2001/XMLSchema-datatypes"
namespace lza = "http://www.laszlosystems.com/annotations/1.0"
The a: namespace defines some standard annotations like a:defaultValue, and the lza: namespace defines some custom annotations private to the Laszlo compiler like lza:visibility and lza:modifiers. Thanks to the ability to annotate the grammar, much of the syntax and semantics of the Laszlo programming language are defined directly in the Relax NG schema in the compact syntax, so any other tool can read the exact same definition the compiler is using!
To show how truly simple and elegant it is, here is the snake eating its tail: The Relax NG XML syntax, written in the Relax NG compact syntax:
# RELAX NG XML syntax specified in compact syntax.
default namespace rng = "http://relaxng.org/ns/structure/1.0"
namespace loc
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Totally agree.
While XML may have it's places (I've yet to encounter one in the commerical world), passing large amount of data is not one of them. A good flat file design is a lot more efficent than XML, and short of hardware accelartion I don't see that changing.
I'm currently trying to assist a customer, whose changing from one system to another, the current system generates flat files of approx 2gig in size every couple of days (billing data). The new system produces files of approx 13gig. The data contained within files result in the exact same bill being produced for the customers.
Needless to say, the extra diskspace (yes we do compress them), and processing time to parse/compress is such a waste.
In my mind, XML trades shorter development time / 'portability' (well so the theory goes), for greater resource usage (CPU/Disk), whereas most customers I've dealt with would rather take a little longer to develop, and have a lot less resource limitation issues on the production systems. The old methods of 'just throw more hardware at it' just don't work in the real world anymore.
Relax NG is a great example of the triumph of Design-by-Inspired-Individuals vs. Design-by-Committee.
In The State of XML, Edd Dumbill explains the secret behind the success of Relax NG:
-Don
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With a notation similar to RELAX NG compact syntax. XML has been a killer of readable formats like windows-style ini files. It tries to be readable by both human and machine and succeeds at neither. It's like programming in assembler, because it can be read by a human better than machine code and compiled faster than C.
XML was designed with people in mind, which is why it's easier for people to read and manipulate than your traditional binary file format.
Err... no.
XML was a step back from SGML's "human-friendly" clever tricks. XML was intended to be easy to PARSE, not easy to read.
Blasphemy is a human right. Blasphemophobia kills.
Tim Bray is right, and he couldn't have put it better: W3C XML Schemas (XSD) suck. The reason Relax NG is so much cleaner and more powerful than committee-designed XML Schemas, is that it's based on a sound mathematical foundation (tree regular expressions, or "hedge automata theory"). While XML-Schemas suffer from ad-hoc design, committee-burn, lack of focus, and half-baked attempts to solve too many unrelated problems.
Here's some interesting stuff from my blog about the design and development of Relax NG.
-Don
James Clark wrote about maximizing composability:
Clark describes the derivative algorithm's lazy approach to automaton construction:
The Relax NG derivative algorithm is implemented in a few hundred elegent declarative functional lines of Haskel, and also in tens of thousands of lines and hundreds of classes of highly abstract complex Java code.
Clark's Java implementation of Relax NG is called "jing", which is a Thai word meaning truthful, real, serious, no-nonsense, and ending with "ng".
Comparing the Java and Haskell implementations of Relax NG illustrates what a wicked cool and powerful language Haskell really is. The Java code must explicitly model and simulate many Haskel features like first order functions, memoization, pattern matching, partial evaluation, lazy evaluation, declarative programming, and functional programming. That requires many abstract interfaces,, concrete classes and brittle lines of code.
While the Java code is quite brittle and verbose, the Haskell code is extremely flexible and concise. Haskell is an excellent design language, a vehicle for exploring complex problem spaces, designing and testing ingenious solutions, performing practical experiments, weighin
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Yeah, well I have to look at EDI every day. I'd switch to XML in a heartbeat if it were up to me.
You picked some obvious strawmen to shoot down. XML isn't for building gigabyte databases (regardless of whether some people try to use it for that). It's for easily moving data between applications. If you think writing a flat text parser is easy, then you've never had to deal with nested data or escaped characters. Say what you will about XML, but it's nice to have one set standard that deals with all that, even if suboptimally, because I never want to write another ad-hoc parser for as long as I live. Been there, done that, have no desire to bother again.
Dewey, what part of this looks like authorities should be involved?
Damn! I mean, add </>...
(Argh, the "wait between comments" thing is infuriating...)
Sometimes it's best to just let stupid people be stupid.
Of course ASCII (or UNICODE for that matter) is a binary standard as well. So special tools called text editors were created so that people could read it.
There are more sophisticated binary standards that are more efficient than ASCII and it wouldn't take a lot of effort to create viewers/editors for them as well. Of course most markup documents would be significantly smaller if tags didn't have to be S-P-E-L-L-E-D O-U-T character by character. Each HTML tag could be encoded in just two bytes with lots of room to spare.
It always fascinates me that we have no problem making customers use a new specialized tool like a browser, but it's taboo to use a non-ASCII tool for development. So we continue to structure our data as if it were going to be processed by a VT100.
That feature is in SGML. In fact it can be even shorter than that, you can express an entire tag and its content with is optional). SGML even lets you change the angle brackets to anything else you want. You can make any SGML doc look like nothing you or anyone else has ever seen ... all part of the feature set.
SGML is full of fun little hacks like that, and it was a pain in the ass to read. Omitting the tag name from the end tag makes it impossible to know you have an improperly closed tag til the end of the document, and then you have no idea which tag wasn't closed. And no, that wasn't a theoretical problem either, this became a real problem with giant SGML docs that used all the shortcuts.
If you really hate XML's verbosity so much, realize that it was designed for easy reading, not easy writing. I whipped up my own xml mode in emacs and made '</' trigger an "electric-slash" behavior that closes the tag automatically. Not rocket science.
Done with slashdot, done with nerds, getting a life.
If XML Schema was a work colleague they would be Wally from Dilbert - it's not that things are impossible to do with it, it's just that the relative simple things become hard and the complex almost impossible. Due to the fact that almost anything is possible with XML schema with enough work (weeks, months years...) instead of just scrapping it, people keep at it doggedly despite the number of times we get bitten. I'd love to see the community move more completely to RELAX NG if it makes my life easier.
From the xml-dev mailing list:
From: Rick Jelliffe
To: xml-dev@lists.xml.org
Date: Wed, 29 Nov 2006 12:46:06 +1100
Robert Koberg wrote:
Maybe a better analogy would be that the people who say that XSD is lovely is Mr Bush's "Mission Accomplished!"
Though of course there are differences between Iraq and XSD. One seems to be about people with their own fiefdom agendas stubbornly miring us in a quagmire, using a grabbag of thin reasons to justify it, denying any evidence that things are not rosy, perpetually promising that things are turning around, and enmeshing all sorts of decent people in a life of horror, difficulty and with no confidence in accomplishing the mission. The other is in the Middle East.
Just joking...
Rick
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So should the lesson here be to "RELAX if you have MONO"?
It's good for transmitting information/energy, but it's not good for storing it.
-Don
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I call this the Line of View (as in PoV) or 'Horizon' Problem. The general problem is this: In XML we've got a standard that is universal for displaying n-dimensional structures in a basically 1-dimensional enviroment. (For the time being, we're ignoring that XML text ususally goes from left to right and top to bottom, making that something 2D to look at) ... At some point you will have to look at in which way you want to handle your stuff and which way you're going to unravel it. This will undoubtly influence on how much XML clutter you will have to construct. With XML it's the same as with databases: It/they will allways be pathetic crutches for us to latch on to the real work. Undispensable, but crutches nontheless.
The question now is: where do you draw the line of view? Along which line do I take my knife to cut open my n-dimensional structure to unravel it and flatten it out into a 1-dimesional string of characters? This is a problem that is impossible to solve satisfactory for all possible PoVs or - as I say - Lines of View, or better yet, Horizons to the structure. Will I unravel my DB of books by authors? By issues? By vendors? By publishers or by weight and size?
What I'm getting to is this: mapping n-dimensional stuff to 1-dimensional structures will allways suck one way or the other. It's just that with XML we all start agreeing upon in which way it's supposed to suck. I don't think that changing the Schema standard (or worse: introducing additional standards) will actually attack this hard problem. I have a strong suspicion that Relax NGs relief is illusional, short term and re-introduces downsides that XML Schema allready has takled with it's pesky and strict nature. For one it would be consistency with the View-Horizon once chosen all the way through the given data-structure. I don't know for shure - go test and find out - but I do know that universal serialization will allways come with downsides and RelaxNG (or any other schema) won't change that.
We suffer more in our imagination than in reality. - Seneca