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XForms Essentials
The motivation for XForms came from a realisation that the Web has pretty much ignored the needs of forms-based sites up to now, beyond the simplest and most trivial of uses. That more complex forms do exist on Web sites today says more about the ingenuity of their authors than about the utility of HTML forms. XForms is designed to make form authoring, maintenance, deployment and redeployment to different platforms, work.
XForms removes the need for reams of script to make a web form function. No longer must you code business (or any other sort of) logic right into the UI. Instead, you write rules against the XML data structures you want forms to populate (that's right, data structures, not name value pairs, unless that is actually what you want). XForms lets you bind the UI to the data structures directly (or indirectly, if you want to be really clever). The UI responds to changes to the data, rather than the other way round, and suddenly life really does become much easier. Granted, you must first make the mental leap from a procedural to a declarative frame of mind, but once that is achieved you will soon be reaping the benefits.
Rather than pontificate on the wonders of XForms (and I am biased, being a Working Group member), I would urge you instead to take a look at Micah Dubinko's book. (Micah is even more biased than me, having been a Working Group member for much, much longer.) No purchase is necessary; you can read the full text online, though I will admit that even I did end up getting the hard copy eventually. The book is small, and paper still has something over HTML, even when viewed on an Apple PowerBook.
Given that you can read Micah's book on the web, I really would urge people to look at it before attempting the rec. itself. The intended audience for the XForms rec. is the XForms implementer, rather than the XForms author. So, short and well-written as it undoubtedly is, this is not an easy read. If you are not sure how much time to invest looking at XForms, you could do worse than read the first chapter of Micah's book. It explains why XForms is as it is, and how it got there. It lays down the principal problems with HTML forms, and explains how XForms is better.
Having roused your curiosity in Chapter 1, the second chapter works through an example form. It introduces the reader to XForms functionality, and points to the ways in which XForms is built on a foundation of much-loved and popular W3C recommendations, such as XPath, XML Schema and CSS. Fortunately Micah does not assume that the reader is fully conversant with these technologies; he has written very serviceable introductions to them in subsequent chapters.
Most of XForms Essentials is a reference to the XForms recommendation, with enough examples and usage notes to make entries useful to beginners and old hands alike. Micah provides tips on how to get the most out of XForms, and how to miss the most common pitfalls: for example, how to avoid the need to write complex XPath expressions. There is even a dedicated troubleshooting chapter which people will probably find invaluable, for a while at least. However, as your forms become more ambitious, you will probably hit problems not dealt with by Micah. I think this is inevitable, given the youthfulness of the standard and its implementations. Micah has said that he will update the text as necessary. People should watch his blog site to see what Micah adds.
Micah's text is concise and pithy throughout. Consequently, one of the chief virtues of XForms Essentials is that it is short. To be fair, this partly stems from the conciseness of the XForms recommendation itself. However, it is also an indication that some topics are only covered briefly. For example, there is very little mention of security issues. XForms Essentials certainly doesn't tell you how to deploy forms onto the web. I suspect that some omissions result from the lack of a body of XForms deployment experience as yet as much as from a desire to keep the book short and focused. Micah does, for example, make some useful suggestions about authoring best practices, but these are necessarily sketchy. They do get you thinking, though, about the possibilities opened up by XForms.
The final chapter covers extending XForms. At the moment this mostly means how to use scripting with XForms. I suspect that people initially drawn to this section will ultimately not find it nearly as useful as they first thought, as XForms really does remove the need for most scripting. However, it would be ridiculous to suggest that scripting does not have its place in web development, and Micah suggests what that place might be.
Micah has combined several functions in this book. XForms Essentials answers the question of the moment, "Why XForms?", and so helps to justify interest in yet another W3C recommendation. It is a very good introduction to XForms for the complete beginner, and a handy, desktop reference for the everyday author. You may only read the outer chapters once or twice, but the core of the book will remain invaluable.
What is really missing from the book is any good information on XForms implementations. This is fair enough, the book will remain useful as implementations come and go. However, Micah has written an article describing ten XForms implementations. The article is up-to-date enough to be very useful. The fact that Micah was able to find ten implementations already speaks volumes for the interest generated by XForms (as well as suggesting that the spec is quite implementable). Please bear in mind that Micah's list is selective, not exhaustive!
I have now spoken to a number of people new to XForms (as are we all just now), many of whom use Micah's book, and all report that it is a useful resource to have around. Every one has ended up buying it in the end.
Mark Seaborne works as a technical architect for Origo Services Ltd, the XML message standards body for the UK Life Insurance Industry. When your eyes get tired, you can purchase XForms Essentials from bn.com. Slashdot welcomes readers' book reviews -- to submit a review for consideration, read the book review guidelines, then visit the submission page.
I tried to find the source code to Xforms-1.0 (libforms.so.1), but the download page says it was pulled for some reason. I need it for a LyX upgrade.
When all else fails, run.
IIRC, xforms finally went GPL. Too late though -- GTK+ and Qt were superior even in their 1.x releases, and the world has changed a lot since then...
Also, LyX now has a Qt port AFAIK.