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Effective XML
Before I tell you what's inside though, let me tell you what you won't find in these pages. Primarily you need to know that this book does not teach XML. I know a lot of books say that, yet still include an introduction or appendix that covers the basics, but this isn't one of them. You're expected to know XML from page one. Even syntax is only covered from a proper usage angle. Personally, I appreciated this. It always bothers me when an obvious non-beginner's book starts off by wasting a chapter on things I should already know. You just need to be aware when you buy that you won't learn XML here. Knowledge of namespaces, DTDs, the W3C's Schema Language, XSLT, and more aren't strictly required to get something out of this book, but they certainly would help you get a lot more out of it.
What you will get here is coverage of fifty miscellaneous topics spread across four sections on "Syntax", "Structure", "Semantics", and "Implementation". In "Syntax", ten topics delve into the details of things like DTDs, entity references and the XML declaration itself. It may sound silly to dig deep into a single line of XML that simply declares the format, but I doubt you will think so after reading that topic. There's a lot going on in that line and you want to be in control of those decisions instead of just copying and pasting. Entity references are an even smaller chunk of XML output, but they too get illuminated by a rare insight on how and when they should be used, and for what. Did you know that it is possible to write a namespace savvy DTD? I do now and I learned that in this section as well.
The second section of the book covers "Structure", and to me it was the best part. This collection of seventeen topics is loaded with good advice about how to build an XML document that will be ideal for anyone who needs to work with it. Here you see how metadata should be stored in XML, get tips on embedding binary content, learn which schema language is better for which tasks, and finally understand rare XML constructs like processing instructions and exactly what they are for. Additionally, there's a lot of general advice on the right way to mark up content that's really worth its weight in gold. Just one example of what I learned here is that I under appreciate mixed content for great constructs like <name><given>John</given> <family>Doe</family>, <title>Ph.D.</title></name>. If you like that, you'll enjoy this whole section.
Section three, "Semantics", deals primarily with parsers and their APIs. Again, you won't learn any APIs here. What's covered is their strengths and weaknesses and why you should choose a given API for a given task. SAX and DOM are the main focus of these ten topics, but there are other details sprinkled in, like XPath.
The fourth and final section is all about "Implementation". The thirteen topics here address client-side XML styling, server-side transformations, signatures, encryption, compression, and more. My favorite topic here was a terrific coverage of Unicode and how it affects XML. All developers should know at least as much about Unicode as what's printed here and this is a fine source to learn it from.
One thing that really stands out in the whole text is that the author isn't afraid to cover the dark side of XML. He will tell you where the design process was less than perfect, which tools have little practical value, and some of the problems with where XML technologies are headed. This isn't complaining though. All of this is targeted at how it affects XML developers today. You learn what you can safely skip and what should be outright avoided. The author even tells you what XML is bad at and gives you advice about when you shouldn't use it. That's the mark of a man who knows his subject, if you ask me.
All told, I think the author failed to completely convince me his way is perfect on only 2 topics. That means I learned 48 expert XML tricks. Surely that's worth the cost of the book in time and money. This isn't the first XML book you need, but I think it is the second XML book everyone should read.
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Is that it's not a very machine-friendly language (more wordy than it ought to be; parsing of tags is not very efficient) and it's not a very human-friendly language (the human style is free-style, really). I don't think it's a very good universal data description language. sorry that I had to go on a bit of a tangent...
Surely you mean physics book a lagrange
XML: You killled my father!
HTML: No, XML....I am your father!
XML: That's impossible!
HTML: Grep your code...you know it to be true.
XML: NOOOOOOOOOOOOOOOOOO!
____
~ |rip/\/\aster /\/\onkey
I want to say something funny about XML, but there is nothing.
-pyrrho
XML is all about loosely bound interfaces.
Get with the program.
<letter>r bose">verbose</link>.e ><nickname>Letter</nickname></name>
<salutation>Dear XML-Junkies</salutation>
<body>
I type all my business letters in <link href="http://www.google.com/?q=XML>XML</link>. Sometimes it can be a bit <link href="http://dictionary.reference.com/search?q=ve
</body>
<signature>
<nam
</signature>
</letter>
XML is totally overhyped, which sadly makes people think it is a lot more complex than it is.
Think of it more like CSV than mySQL. It's just a format for representing structured data. It also happens to be that it's quite easily read by humans.
Yes, you can do incredibly advanced things with XML, but there is nothing you can do in XML compared to your own propietary data storing language.
The reason people use XML instead of writing their own data storing format is simple:- there is a lot of tools for parsing it, which you'd have to write yourself if you had your own format.
As for the javascript and XML example, it's impressive, but it's far more javascript than XML.
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RelaxNG, for instance, lets you verify that your XML file is built correctly for your app: you write a RelaxNG spec for your XML file format, and then it verifies that all the mandatory fields are there, in whatever order is necessary, with the correct datatypes, etc, etc. RelaxNG processors are part of most major XML libraries now, so if you're writing Perl you can just tell your Perl library to validate your file and it's done. If you're editing in Emacs (with nxml-mode), you can point Emacs at your RelaxNG file, and have tab completion, error highlighting, etc, etc-- all customized for your file format.
XSLT lets you take an XML file and perform transformations on it into another (possibly XML) file format. Need to convert XML into SQL INSERTS? Piece of cake. I use it to extract particular parts of an XML file and convert them into a significantly differently-ordered Lisp structure.
Most modern web browsers are becoming CSS engines rather than HTML engines. So you can stick a CSS stylesheet reference at the top of your XML file, and have the CSS generate something that looks like what you want the user to see. The data file looks good to the app, and looks good to the user. You can also (with some browsers) use more powerful transformations using something like DSSSL or XSLT.
DOM for a standard data manipulation API, so each program you write doesn't have a different data access language. XPath as a language to perform more complex queries. XML Namespaces to let users or apps tag their data with extensions. XInclude for data sharing. All of these are things you get for free with XML.
All of these are general technologies, not specific apps. So they should be usable in most major libraries in most languages. (If you're using Perl, I'd recommend XML::LibXML.)
Don't think of XML as just a file format, because that part sucks. Think of it as a buffet table of technologies. When you write a program, 10% is to do the program's processing; the other 90% is to handle I/O, data management, and other housekeeping. Using XML lets you get a lot of that for free.
PS: I'm not an XML fanatic. A year ago, I was told to use XML for one particular project and was disgusted at the idea. I still think that XML gets a lot wrong, but I've come to recognize what benefits XML provides.
There are valid uses for XML. Just look at http://www.x-cp.org/
Ever try to debug deeply nested LISP in a plain vanilla text editor? Ever try to find exactly which closing parenthesis is missing where? That's why end-tags have names. It's pure human factors. Computers don't care about this. People do.
SGML (XML's precursor) did have minimized end-tags like . Experience proved this caused more pain than it alleviated. Hence the lack of minimized end-tags in XML.