I’m pondering implementing the computational parts of the XForms Model in XQuery. Doing so in a largely functional environment poses some challenges, though. Has anybody tackled this before? How about in any functional language, including ML, Haskell, Scheme, XSLT, or careful Python?
I borrowed the book Purely Functional Data Structures from a friend–this looks to be [...]
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XiX (XForms in XQuery)
Submitted by administrator on Thu, 10/30/2008 - 22:07.Introduction to XForms
Submitted by administrator on Thu, 07/24/2008 - 02:06.A key idea of our approach to building internet applications is making good use of standards-based languages, in particular XForms. XForms is an exciting new language from the W3C that can be used to create anything from simple forms to complex Web 2.0 a
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Tags: forms, formsplayer, gcwebteam, programming, standards, todo, w3c, webservices, xforms
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Submitted by administrator on Thu, 02/14/2008 - 09:29.XForms Virtual Meeting 2008
Submitted by administrator on Fri, 02/01/2008 - 16:56.Today we had our first XForms WG virtual meeting day ever. We used our regular W3C Zakim teleconferencing bridge in combination with Yugma a free desktop sharing application. We mainly talked about XForms 1.2 requirements and new features.
Tomorrow I will leave for Durham for the three day face to face meeting of the XForms WG at the IBM Research Triangle Park Executive Briefing Center. During those three days we hope to create the outline for the XForms 1.2 requirements document, discuss some of those new features, and do some work on XForms 2.0. More news on this will follow.
Yahoo! uses XForms for 'write once, run anywhere' mobile applications
Submitted by administrator on Tue, 01/08/2008 - 15:44.Yahoo! recently announced their entry into the mobile web applications space, with a service that allows applications to be built and hosted using Blueprint, a purpose-built mark-up language based on XForms.
The Blueprint roadmap describes the underlying philosophy:
Much of Blueprint's philosophy and syntax comes from XForms. We opted for a full declarative language because it was the only way we could effectively run on the wide range of devices out there, some of which have no scripting at all. By using declarative syntax, we can encapsulate and hide the scripting specifics. In some cases, the code could run on the phone, in other case, such as XHTML, we can put the logic on our servers. It's the perfect way to deal with the various environments and their capabilities.
At the moment Blueprint is simply converted to XHTML plus JavaScript for delivery to devices, but the mention of XForms gives a clear indication of where they are heading. And given that Google did something similar with the launch of its Google Mashup Language, it all bodes well for a new wave of web applications that won't be built using JavaScript (or even Java and GWT) but will use straightforward, device-independent, mark-up.
Write once, run anywhere, anybody?
For more on why XForms is Ajax on steroids, see:
www.w3.org - XForms 1.0 Quick Reference
Submitted by administrator on Thu, 01/03/2008 - 05:56.XForms 1.0 Quick Reference.
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en.wikipedia.org - XForms - Wikipedia, the free encyclopedia
Submitted by administrator on Thu, 01/03/2008 - 05:51.Sidewinder and the need for a semantic web applications framework
Submitted by administrator on Tue, 08/28/2007 - 19:23.A couple of recent discussions in the RDFa and microformat communities concern areas of particular interest to those of us working on Sidewinder, a semantic web applications framework.
The initial discussion is taking place on the microformats lists, and concerns how to allow authors to indicate what actions are available to be performed on items appearing in a document. The second discussion is taking place on the 'RDF in XHTML Task Force' list; this post provides a good summary of some of the issues.
All in all I find these very exciting discussions, because they concern exactly the types of use-case that prompted me to get involved with the XHTML work at the W3C a number of years ago.
This was because I'd been trying to create the kind of flexible user interface that these threads are describing--no doubt just as lots of other people had--and in my own endeavours I ran up against a number of very serious problems that made me conclude that it was pretty much impossible with the technologies available at the time. And since I still haven't seen a convincing solution to the problem of creating extremely flexible user interfaces, I've concluded that the issues I ran up against are of quite a fundamental nature.
Some of the problems that seem to me to be absolutely necessary to solve are:
- an HTML page contains insufficient metadata about what its content 'means', making it difficult to work out what kind of UI constructs to render;
- even were you are able to work out what the data means, HTML is not itself powerful enough to express the kinds of complex user interfaces that you would want to 'bind' to this underlying data;
- and even if you work out what the data means and define complex UI components, you still can't define binding rules that indicate what widget to use with what data;
- the browser offers only one 'paradigm' for interacting with information of interest, whilst we often want to create applications that can make use of the same rich features.
For every problem...
The first problem--that HTML is not 'rich' enough--is now largely solved by RDFa. It has taken quite a long time to get here, but I think the effort that has gone into getting RDFa right is going to be worth it. The key thing that RDFa does is to get RDF into HTML--once you've got that, all sorts of possibilities open up.
The second problem--that it's difficult to define rich user interfaces with only HTML--is largely solved by XForms. That XForms is a solution is currently not obvious to most people so XForms remains peripheral in application development at the moment. Of course it is possible to define widgets using script but it quickly gets very messy. There is also an enormous problem of re-use, in the recursive sense; most Ajax libraries are works of art, but very few can support the kind of complexity we need. Take the example shown here:
Here we have widgets that are made up of other widgets to an arbitrary depth, but the key thing is that the binding mechanism is based on abstractions; it could be the run-time data type or an abstract widget type, and in both cases it means that at any point in the hierarchy a different widget could be swapped in without disturbing anything above or below. This kind of complexity is extremely difficult to achieve with procedural languages. (See also Introduction to custom controls and Understanding the MVC separation.)
The third problem--the use of binding rules to indicate which widget should be connected to what data--is still a little in the air. One part of it we've solved by specifying binding 'rules' using XPath selectors that are data type aware. This means that we can indicate that data of type 'geo location' should have one set of behaviour bound to it, whilst data of type 'time' can have a different type. These are essentially binding stylesheets and I think this is where we can answer the question posed on the RDFa list as to whether it is the author, the end-user or the browser vendor that should be in control of the widgets--the answer is all of them! By allowing users to express binding rules that override those from authors, we can achieve the best of both worlds.
Finally, the problem that the only paradigm we have for interacting with web-based data is 'browsing' is what we are trying to solve with Sidewinder. The ultimate goal is to have a framework that can be used to build any type of internet-facing application, whether web or desktop based. By allowing all applications to make use of the same semantic functionality and the same binding rules we can allow the users themselves to get control of their data and their applications. (See also Web 2.0, Copernicus and Sparticus: Moving the centre of the web.)
Once you have this kind of 'platform' (see Platform 2.0) then things really start to open up. I could build a clock widget using Silverlight, perhaps, and have that appear anywhere that the time data type is used--whether in my messaging client, my email client, my Twitter gadget, my Facebook desktop notification system, and so on. But you might choose a clock built using SVG, whilst someone else might decide to have a clock that speaks. But any of us could swap one of these behaviours for another at will, for a component we have created or one that we have downloaded from elsewhere--the ultimate, flexible, programming platform.
Ajax and progressive browser enhancement
Submitted by administrator on Tue, 07/17/2007 - 10:35.Progressive enhancement is an approach to web development that has been around for a few years now. (More on PE at Wikipedia.) At its most basic it suggests building our web pages in a 'clean' and uncluttered way, and then layering functionality onto the mark-up using various mechanisms, such as stylesheets and scripts. The idea is that browsers without the additional capabilities can still render the page in some fashion, but those with additional power--such as scripting support--can add more enhanced features.
This principle actually underpins much of the work we've been doing on XHTML 2, which has involved taking HTML back to its semantic roots. In particular the work on RDFa has been to a large extent motivated by providing more semantic 'hooks' on which to attach increasingly focused functionality. (The work pre-dates the term progressive enhancement, so it isn't generally called that.)
But there is a new phenomena afoot, which I'd like to call progressive browser enhancement. It's something we've been doing for a while with our work on XForms and formsPlayer, but it also has wider applicability.
DOM Events and standards
To illustrate the idea of PBE, let's look at eventing in the browser. Many Ajax libraries have their own eventing architecture, and they are without exception non-standard. This is a shame, since the W3C has a standard for DOM events (DOM 2 Events) which has been around for years and is very clearly defined. Of course, part of the problem is that whilst it has been implemented in Firefox, Safari and Opera, it's not available in Internet Explorer. This meant that when we began our work on formsPlayer, our XForms processor plug-in for Internet Explorer, we had to implement a DOM 2 Events component ourselves.
This does however mean that DOM 2 Events support is potentially available for all browsers, but of course the problem now is that in order to make use of it on IE, people would have to install formsPlayer. And even if we made the module available separately (which we will be doing shortly), the problem for the programmer is that they can't assume that it is installed; there is still an annoying rift between those who have browsers with DOM 2 Events support, and those that don't.
Using JavaScript to enhance the browser
To fill the gap we simply implemented a DOM 2 Events library in JavaScript. Whilst most Ajax libraries went the route of creating their own non-standard eventing architectures, we went the other way and implemented the standard. The advantage of our approach is that if our end-user is running a browser with reasonable standards support such as Firefox, Opera or Safari, they'll get native support for DOM 2 Events, and hopefully a faster experience. Similarly, if our user is on IE and has installed the formsPlayer DOM 2 Events component, they will likewise get a faster experience. It's only the middle group using the scripted version of DOM 2 Events who will have a slightly slower experience.
But the key point is that the end-user now has some control, since they can add a DOM 2 Event component if they want to--most likely as part of some other package--independent of the actual web applications they are using. And for the authors of web applications life is much easier, since they are coding to a standard, rather than being forced to code to the specific event architecture of YUI, Dojo, or whatever Ajax library they want to use.
This is the key idea of progressive browser enhancement.
Threading in Google Gears
Another example of PBE is threading in Google Gears. There are a number of JavaScript libraries around that create simple threading by using the timer in JavaScript. This is fine for a lot of uses but can affect performance. However, we can follow the same approach as I described above for DOM 2 Events; if the function calls that the programmer makes to create a thread are 'standard', then although in normal operation the less-efficient JavaScript version would be used, with no change to the code the web application can take advantage of 'proper' threading, should a user have Google Gears installed. (See also: Ajax makes browser choice irrelevant...but we still need standards.)
Of course, most users are unlikely to be looking for a threading library to install, just as they will not be downloading a DOM 2 Events module. But if these components are small enough to be bundled up with other pieces of software they will gradually find their way onto users machines as part of other, useful, packages.
However the distribution takes place, it's the end-users of our web applications that are in control of progressively enhancing their browser, not the web application programmers themselves.
These principles have underpinned the design of Yowl, a centralised notification system for web applications.
Yowl centralised notification system
Yowl is a way of providing notifications to users of web applications, but in a way that the user themselves can control. It was inspired by Growl, which runs on the Mac, and which is used by applications such as Skype and Adium; by passing all notifications through a central system users are given the power to decide which messages they are interested in, and how they want to see--or even hear--them.
Progressive browser enhancement allows Yowl notifications to make use of advanced features in the browser if they are available, but to fall back to basic notifications if not. For example, we've created a Windows component that allows messages to be displayed above the system tray. The component is invoked and called from script, and works with both Firefox and Internet Explorer:
However, if the systray component is not installed, the Yowl notification system will simply use JavaScript to show messages within the browser window. You can see a sample of the non-enhanced notifications here--it will run in all the major browsers:
The programmer need change nothing in their code to make use of the systray component if it is present, since as with the DOM 2 Events example, or Google Gears and threading, the user is in control of the browser enhancement, not the programmer.
(For more on Yowl see the Yowl open source project page, Yowl: Design principles and how to use it and Yowl: An open source centralised notification system.)
Where does this leave the browser?
There is still plenty of scope for the browser to evolve and make available the kind of features we're talking about here. But the truth is that progressive browser enhancement makes browser evolution far less significant than it has been until now. That's probably not a bad thing, given the chaos that is currently surrounding the development of HTML since the W3C gave its support to HTML 5; the spec itself is becoming increasingly top-heavy, and bears little relationship to the early principles of HTML. Far from having enormous 'kitchen-sink' specifications, PBE looks to add new features in a more nimble way, via small and focused modules.
Of pots and kettles (more squabbling between Sun and Microsoft about standards)
Submitted by administrator on Tue, 07/10/2007 - 09:14.Peter Korn at Sun has obviously decided that there is some mileage in promoting the idea that Microsoft's Open XML Formats is not very accessible. Fine. You can never have too much accessibility, so I'm not going to get upset about that. But in the process Peter believes it worth pointing out that Microsoft don't hold to standards:
In addition to these important questions [lack of accessibility], this white paper nicely sidesteps what I believe is the intent of WGAG 1.0's Guideline 11: "Using W3C technologies and guidelines", and most specifically checkpoint 11.1 "Use W3C technologies when they are available and appropriate for a task and use the latest versions when supported." Unlike ODF, MSOXML makes almost no use of existing W3C standards. Instead of using the W3C XForms specification for embedded forms, it invents its own XML terminology for forms. Instead of using the SVG specification for vector graphics, it uses its own vector graphics encoding. Instead of using the MathML specification for mathematical equations, it uses its own math encoding.
All true, of course...all true.
But I've spent a few years in and around the W3C (as an invited expert in the XForms Working Group and the XHTML Working Group), and I've seen up close how all the big companies pick up and drop one or other standard as it suits them, so I can't really take Peter's points that seriously. Much like the idea of open source, standards are a great thing--and much like with open source they become a site for politics and marketing. So as you'd expect, Gray Norton--the main target of Peter's ire--is not about to miss an opportunity to have a dig back, so in his reply on Peter's blog he points out that MSOXML is not the only format not making use of other standards:
Speaking of PDF, would you mind please pointing out the list of W3C recommendations supported by PDF/X-1a, PDF/X-3 and PDF/A? It’s been a few years, but I don’t recall the use of XForms, SVG or MathML in these specifications. These are all ISO standards today, so I’m curious to compare this with the ODF example you cited in your post.
Once again, that's true enough.
I have no interest in taking sides here, but it does annoy me that it's taken for granted that the world is made up of Microsoft who flout standards, and everyone else who doesn't. It's particularly ironic in this example since Gray needn't have gone as far afield as PDF to point out lack of XForms support--he could have looked at ODF itself. Whilst the Open Document Format may well have adopted the XForms model, they've not used any of the form controls. And worse, some of the bindings they have used to connect the controls to the model are non-standard (they've made buttons bind to submissions, rather than model data).
But I'm not at all criticising ODF for this; what does it matter if only some part of XForms is adopted today in ODF? If it does the job then that's great. If there is any positive criticism to level it would be at the XForms standard itself for being insufficiently modular to facilitate its use in other formats.
In short, when everyone is at the same game of promoting one or other standard for commercial or political mileage, it's worth trying to read between the lines a little. Which leaves us only one basis on which to judge any standard--whether it is actually any good for the task at hand.
Dynamic user interfaces and XForms' performance
Submitted by administrator on Mon, 04/09/2007 - 12:02.An interesting question has been raised on Linkedin Answers:
What is your opinion of formsPlayer, the XForms development environment, with regards to developing dynamically configurable UIs where throughput is critical?
Although phrased as a question about formsPlayer, it gets to the heart of important issues that concern XForms, so it's worth seeing this as a collection of separate but interrelated questions. The first question is essentially about how appropriate XForms is for developing dynamically configurable UIs, whilst the second relates to whether there are performance issues to watch out for. Having established whether XForms is suitable, the third question asks if formsPlayer specifically, is right for the job.
Since solving the problem of dynamic user interfaces is exactly the reason I got involved in XForms in its early days, this was bound to be a question I'd have an interest in, even if it hadn't mentioned formsPlayer.
Dynamic user interfaces
A number of years ago much of my work was based around content-management systems. Although my company built a number of different applications and took a number of different approaches to the problem, the common factor in everything we were investigating was the desire to create flexible user interfaces. We nearly always came up against the limitations of HTML in what we were doing, and as a result we nearly always found ourselves defining user interfaces in some hacked together UI language...until one day I stumbled across XForms.
XForms as a UI definition language
Initially we simply used XForms to define user interfaces, which were then translated into HTML. XForms was perfect for the job because it allowed UIs to be defined in an 'abstract' way, independent of any platform or system. This was important because other languages that could be used--such as XUL--were insufficiently abstract and focused too much on GUIs. (And although HTML is to some extent abstract, it just doesn't provide enough of a feature-set.)
In some ways both of these problems had already been overcome by defining our own intermediate forms language, but XForms was not only more powerful, it came from the W3C, and we felt it important to use standards (standards often lead to productivity benefits).
XForms as a run-time language
Of course it wasn't long before we decided that passing XForms through an XSLT processor in order to produce static HTML was nowhere near as interesting as processing XForms at run-time, and we decided to spend some time producing a run-time processor. We worked on a number of different architectures, all of which were useful in different contexts, but the one we decided to put most effort into was our browser extension, formsPlayer.
By putting XForms into the browser we were able to speed up our form development times (edit your form and press F5), as well as improve performance and the range of features that we could support. Other developers took other routes, and now, a few years on, there are a wide range of XForms processors, each reflecting a different approach to the architecture, and encompassing a variety of platforms; there are solutions for mobile devices (PicoForms and MoviForms), browser extensions for both Internet Explorer and Firefox (Mozilla XForms and formsPlayer), and of course sophisticated server-side transformation engines (Orbeon and Chiba).
(XForms processors can be built with such a broad range of architectures because of XForms' MVC structure, which I hope to discuss in another post.)
XForms and performance
Whilst it's clear that XForms is an ideal solution for dynamic UIs, it has to be said that it is not (yet) a silver bullet that will hide issues with the underlying architecture. Just as when building an ASP, JSP, Rails--or whatever--solution you need to get your architectural approach right for the task at hand, so too with XForms. Issues such as getting the right data at the right time, or creating modular and manageable forms, will still need to be taken into account.
One problem we see a lot in our consultancy work is that XForms gets treated as a programming language like Visual Basic, rather than a web-based technology. As a consequence, authors tend to create very large forms, often with numerous instances each importing a large amount of data on document load. This is often compounded by using XSLT to generate the forms, creating a great deal of avoidable duplication, and resulting in even larger forms.
These are not practices that an Ajax, Java or C++ programmer would follow whilst building an application, but because XForms is so powerful, it presents a great temptation to the author to create monolithic forms without consideration to what is going on 'under the hood'.
HTTP and concurrent requests
For example, most Ajax programmers--at least those who program to the metal--will tell you that there is no point in sending more than two concurrent HTTP requests to the same server, since the third and subsequent requests will be blocked by the browser until the first or second completes. This is not a browser limitation, but a consequence of the HTTP specification, and the effect is to slow down the loading of the main document if all the required images, stylesheets and scripts are placed on the same server.
If you look at Google Maps or Flickr, for example, you'll see that the image URLs make reference to lots of different servers; you may have assumed that this is to do with distributing server load, but it's not (that problem can be addressed in other ways), and is in fact to do with finding a way to allow browsers to load more external files at the same time, and so improve overall load time. If all Flickr images or Google map tiles were stored on one server then the elapsed time for loading four images into your browser would be the amount of time taken to load two images, one after the other. (I.e., two are loaded simultaneously, followed by another two.) But if those four images were each on separate servers, all four could be requested at the same time, and the elapsed time would essentially be halved.
Unfortunately, although XForms hides a lot of complexity from the author, this is the kind of thing that XForms can do nothing about--it won't matter what XForms architecture you use if the transport protocol is HTTP. This means that if you have a number of instances in your form, each loaded via the src attribute, the initial load time will be limited by the fact that only two instances can be loaded simultaneously. And since the UI won't usually be available to the user until all models are initialised, this could create a bad experience for the user.
Of course the good news is that XForms handles data communications asynchronously out of the box, which means that once the data has been obtained, any form controls that depend on that data will automatically be adjusted to reflect any new values. So provided that you get the underlying architecture of your application right, managing XForms itself is very straightforward.
Deferred loading (or 'Google Suggest')
Another common problem caused by XForms making some things just too easy, concerns very large selection lists. In XForms it's straightforward to populate a select1 from some XML data, by using the itemset element. The problem is that authors will often load the necessary instance data when the form first loads--well before it is ever needed--and worse, this data could be quite large.
Once again it's important to think about the principles we would have applied if we were writing a C++ or Java application--or even an Ajax one--that was going to obtain data from the internet. For a start we would probably consider loading the data only at the point when we needed it, or perhaps in the background, and in many situations we'd certainly try to load only as much information as was needed.
For example, if we have a large list of chemical compounds or part numbers for a car, there may be thousands or even tens of thousands to choose from. But by connecting a select1 to an instance that is populated with data from the server as the user types--as popularised by Google Suggest--we don't need to download so much data, and we also reduce the size of the list. (See XForms Patterns: Incremental and 'Google Suggest' and Using Google Suggest to Categorise del.icio.us for a detailed discussion of how this is done.)
XForms modularisation
None of this is to say that there are no problems with XForms, and that the only issues you'll ever have are to do with the underlying infrastructure, and as XForms is used for larger and more ambitious applications, there is a lot of scope for improvement at the mark-up level. For example, not only could we defer the loading of some of the data (as discussed above), but we could also defer the loading of some of the form. There is no mechanism in XForms for doing this at the moment, but much of the 'machinery' is in place in XForms 1.1, and it could be quite straightforward. (See Using subforms in XForms for some ideas on this.)
formsPlayer
The final question being asked is simply that if the first two questions are answered positively--i.e., if XForms is a good technology fit in applications that need responsive, dynamic forms--is formsPlayer a good choice as an XForms technology?
The answer to that question will depend completely on the architecture being deployed to, since as we've seen, XForms can be used in many different kinds of environments. For example, Chiba and Orbeon are both great server-side solutions. They work by translating XForms into HTML (or HTML plus Ajax) that can be processed by any browser. The key benefit of using XForms in this way is that it abstracts away much of the logic that would normally be trapped in RoR controllers, ASP scripts, Java servlets, and so on.
formsPlayer on the other hand, pushes all of the processing into the client, which has advantages when it comes to control over advanced functionality (we are able to do things that browsers cannot, such as save-and-resume, off-line working, PDF printing, and so on), but for the time being we only support Internet Explorer on Windows (although versions for other platforms are now being developed).
An interesting bonus of having full XForms support in the client, is that formsPlayer can be deployed not just in web-based applications as you might expect, but also embedded in other kinds of applications. For example, we have a customer that uses fP inside a .NET application that runs on Tablet PCs; this architecture allows them to use more conventional programming techniques for their processing logic (in this case C#), but to use simple XML tools to develop the complex user interfaces that are needed in their industry. In other words, they use XForms to give them more "dynamically configurable UIs" than C# is able to.
(It's worth noting that this is a real problem for everyone, and to some extent it lies behind the motivation for XAML. But in my view, XForms wins over XAML by being a standard.)
formsPlayer therefore meets a different set of needs to server-side solutions like Chiba and Orbeon, so as with any application, developers will need to work out for themselves which XForms architecture is the most appropriate for their project.
Regardless of the model used, it should be stressed that we are still dealing with only one language. Try finding another programming language which would allow you to write an application that could run in a browser or embedded in a .NET application or on a mobile phone...or even as a server-based application, without altering any of the code.
Adriaan de Jonge on XForms and RoR
Submitted by administrator on Tue, 03/20/2007 - 10:21.Adriaan de Jonge's article XForms vs. Ruby on Rails is a must-read for anyone interested in XForms.
You may not agree with all of it, but the author clearly understands the benefits of XForms, even if he ultimately comes down on the side of Ruby on Rails. And he makes some interesting suggestions as to where XForms should be going next.
The following quote is a useful summary of both the power of XForms, and the things we need to focus on to allow it to be used by more and more people:
XForms logic beats any other technique when used in XML documents with semi-structured nature. XForms logic is based on XML specifications and XPath queries. This notation requires a thorough understanding of XML, creativity with XPath, trial and error, and great talent for logical puzzles. For someone with the knowledge and experience of a software architect, the simple tools in XForms can be the building blocks of a very advanced and intelligent application.
Tech Talk at Google on Sidewinder
Submitted by administrator on Wed, 03/14/2007 - 22:01.T. V. Raman, one of the key architects of XForms, invited me to do a Tech Talk at Google. The talk was on Monday, and looked at Sidewinder and our approach to using web languages to create desktop applications--XHTML, XForms, RDFa and so on. Although I really enjoyed doing the talk and having the opportunity to explain at length to a load of techies what exactly it is that we're doing, my overriding memory is already that of the lunch afterwards. Unfortunately, the lunch was not captured on video, although they do record the tech talks:
The abstract for the talk was as follows:
Web applications use HTTP to communicate with relevant services and manifest their user ... all » interface via HTML, CSS and JavaScript. With the advent of different gadget frameworks, they have finally broken free of the shackles of the Web browser to manifest themselves on the user's desktop as first-class productivity tools.
In this talk I'll describe Sidewinder, a framework for authoring and deploying web applications that are created as first-class desktop citizens. Applications created in this framework can not only communicate with the web, but with each other, turning the whole platform into a powerful tool for creating mashup applications. Sidewinder can also turn any other web application into a desktop application, such as GCal, KoolIM, Google Docs, and so on.
Another powerful aspect of the Sidewinder framework is the ability to display custom widgets based on the type of the data being processed--chosen dynamically at run-time. This kind of flexibility is crucial when building desktop mash-ups based on varying sources of web-based information, and Sidewinder goes further by making it easy to process the data-oriented web--including microformats and RDFa.
The presentation will include a number of rich internet applications that use the Sidewinder framework.
mashup* punch-up round-up
Submitted by administrator on Fri, 02/23/2007 - 16:56.
No, last-night's mashup* wasn't really a punch-up...but we did have a thoroughly enjoyable ding-dong on topics ranging from whether the next wave of the web would be sensual or semantic, whether rules-engines were the answer to our problems, whether placing a red cross (or a green tick) against an entry in search results was providing a service or 'policing the web', and much more besides. Combined with a great venue, and some interesting characters to share a bottle of beer with, it made for an enjoyable and interesting evening.
Although the meeting was 'about' the semantic web, organiser Sam Sethi was keen to avoid yet another discussion that remained high-level and abstract, and instead wanted to look at some of the exciting things that can be done once you get your hands on the data. Of course that didn't stop some people from trying to explain what 'semantic web' means, and unfortunately they did so with just enough clarity to convince everyone else that it was an unrealisable pipe-dream.
All of which indicated to me, at least, that Sam had been right when he made the decision to focus the evening on what can be done today. As part of illustrating this, he kicked off with some nice demos of the Firefox extensions Webcards and Tails, both of which process microformats located in the ordinary pages you view whilst you are browsing...and both of which look great.
My demo also involved a browser extension, this time for Internet Explorer, and one we created ourselves using the browser extension features of formsPlayer. The data I used for my demonstration used the RDFa format rather than microformats, and to illustrate what the sidebar can do I used Ivan Herman's home-page (which contains FOAF information) as well as my previous blog entry describing the mashup* event (which contains FOAF and iCal information).
The RDFa browser extension simply parses the HTML document in the main window, and stores any RDFa it finds. Then, using XForms and formsPlayer's ability to render custom widgets based on the datatype of the data, the information from the document is displayed in ways that are specific to each piece of data.
In the case of the mashup* event we have two high-level widgets, one for a person and one for an event. The person widget simply shows a person's name, a link to their email address, and their picture. The event widget shows the title of the event, a link to any further information about the event, a map of the location, and the time the event starts. Both the map and the clock are of course themselves widgets--the first an interactive Google Map, and the second an analogue clock created using SVG:
The architecture of this sidebar is interesting for two reasons; the first is that it allows different actions to be performed depending on the data that has been located, and is something that Tails and Operator allow. But we get further flexibility in our RDFa sidebar when it comes to rendering this information; by allowing the widgets to be selected at run-time, based on the 'type' of the data being shown, we really play to the de-centred nature of the web, and allow users to do what they want with the data that they discover. We need this because RDFa is a generic language, and as such we don't know whether it will be used to carry information about people, events, chemical compounds, items for sale, and so on. But precisely because it's generic we don't need to write a parser for every possible language--we only need one. By allowing different widgets to be displayed depending on the 'type' of the data, we can easily create views on the data that are appropriate to different groups and users.
I resisted the temptation last night to try to explain what 'semantic web' means, so I certainly won't bother trying to do it now. Last night's event convinced me that Sam was right to focus on what we can do with all of this, and the exciting collection of demonstrations makes me think that today, the 'doing' part is making the whole thing feel very real indeed.
New drafts of XML Events 2.0 and XHTML Modularisation 1.1
Submitted by administrator on Mon, 02/19/2007 - 12:07.I've been working with Shane McCarron from the HTML Working Group on a number of different documents lately, and it's great to see them made publicly available recently. The first is a new draft of XML Events 2.0, and the second is a new version of XHTML Modularization.
XML Events 2.0
The new draft of XML Events has features that are specifically geared towards future versions of XForms and compound document mark-up.
Some of the interesting new features are:
- the ability to register and remove handlers at run-time;
- an attribute for executing events conditionally;
- another for repeatedly executing actions whilst a condition is true;
- the ability to create action handlers using script, which means that script can be interspersed with other action handlers.
XHTML Modularization
XHTML Modularization 1.1 (or M12N as is it is often called), is a set of guideines, DTDs and XML Schema modules that provide the basics of XHTML, ready to be recombined in different ways by language designers. An example of its use is XHTML Basic, aimed at mobile devices; this language is a sub-set of the full XHTML, and so uses only some of the modules provided in the M12N 'library'.
It's of particular interest to us at x-port, because we've been using compound document schemas for a few years now, and our work in this area has been fed into how these schemas are structured. We use a language created with M12N--we call it xH--that incorporates XForms, SVG, MathML and RDFa, both to drive the editing of our XForms documents, and to validate documents loaded into Sidewinder. The extension languages are defined as modules, following the principles of M12N, so they could be used in other languages, too.
Understanding the XForms dependency-engine
Submitted by administrator on Tue, 02/13/2007 - 00:28.At the heart of an XForms processor is an incredibly powerful 'dependency-engine'. It works much like a spreadsheet, in that you tell it what calculations you want performed, and then the processor works out when to do them, based on changes that take place in the data in the form, as the user interacts with it. Although this all happens automatically--just as in a spreadsheet--knowing what's going on 'under the hood' will mean an XForms programmer can avoid writing inefficient code.
To help programmers gain a better understanding of this little-discussed part of XForms, I've added Understanding the XForms dependency-engine to our Programming with formsPlayer and XForms handbook.
Comments would be most welcome. :)
formsPlayer.com updated--the first place for XForms programmers
Submitted by administrator on Fri, 02/09/2007 - 17:12. We've been working hard in the last few months on a number of different things. Some are imminent--such as full support for XForms 1.1 in formsPlayer--and some are almost imminent (and we can't talk about them yet). But one that is here now, is the fresh, new, restructured and redesigned formsPlayer.com site.
Thanks to an excellent Polish designer now working in Ireland, who was introduced to me by an Englishman who we worked with on a project for a Canadian customer, formsPlayer.com now has a new look. And I don't mind saying, I think it looks great...thanks Bartek!
Up-to-date
The main change in the site is that being based on Drupal, it is now much easier for us to update, which means that we can add tutorials, samples, articles and blogs whenever the mood takes us--and that's often. We've also moved our bug-tracking onto the site, and of course there are plenty of forums in which people can ask (and answer) questions, as well as share ideas.
Integrated
One of the main advantages of the new site is that everything is completely integrated; a comment in the bug-tracking system can link to a tutorial, a blog entry can link to sample code, an answer in a forum can link to a feature request. Being able to cross-reference everything means that the information and knowledge in formsPlayer.com, about building web applications with XForms, will get deeper and deeper.
With these changes we will continue to make formsPlayer.com the foremost place to go for XForms software, samples, tutorials, forums, and more.
Interviewed on XForms for cubicgarden
Submitted by administrator on Fri, 01/19/2007 - 23:59.Yesterday, myself and Phil were invited by Brendan Quinn to talk about XForms over at the BBC. Since we had no idea what experience people might have of XForms, we began with the XForms and Internet Applications presentation, and then did some demos and a bit of 'view source'.
The presentation included a demo that searches Amazon for books, which we followed with other samples from the formsPlayer.com samples page, such as a Flickr search, Google Maps, Microsoft Virtual Earth, and more.
As it turned out, there was some familiarity with XForms, and there were some excellent questions. Although we tried to answer all of them, we also recommended our tutorial, Introduction to XForms. It covers a lot of material, and walks through how to create two forms; one that that saves bookmarks to del.icio.us, and another that searches Flickr.
After the meeting, Ian Forrester interviewed me about XForms and where it was going, and we ended up talking about web applications, Apollo, Sidewinder, the W3C and innovation, XAML, non-obtrusive Ajax, xforms.org...and whether Kurt Cagle backing XForms is an indicator of future success, or not!
XForms and repeating structures...are they really so special?
Submitted by administrator on Mon, 11/20/2006 - 19:28.In one of discussions in the XForms Working Group recently, around insert and delete, we agreed with Erik Bruchez's idea that if @nodeset returns a collection of nodes then we should process all of them, rather than acting on only the first (the so-called "first node rule"). I like this, and to me it makes code easier to read; I can tell what an author has in mind if I see this:
<delete nodeset="customers/customer[1]" ... />
rather than this:
<delete nodeset="customers/customer" ... />
After we agreed to do this it made me wonder about other situations where processing the entire nodeset might give rise to different behaviour if there was more than one node, and one that leapt out was differentiating between repeating structures and non-repeating structures simply by the number of nodes in the nodeset. For example, if there is only one customer in the instance data, then this (if it were legal):
<group nodeset="customers/customer">
<output ref="name" />
<output ref="telephone" />
</group>
would behave the same as this:
<group ref="customers/customer">
<output ref="name" />
<output ref="telephone" />
</group>
If there was more than one customer, then it would be equivalent to a repeat:
<repeat nodeset="customers/customer">
<output ref="name" />
<output ref="telephone" />
</repeat>
But since the second case (multiple customers) includes the first case (only one customer) why bother ever using anything other than a repeating structure? If you don't want a repeat, simply add "[1]" as we saw before.
Of course the problem would be that using a 'repeat' element when you don't actually want a repeating structure would be awkward to read:
<repeat nodeset="customers/customer[1]">
<output ref="name" />
<output ref="telephone" />
</repeat>
or:
<repeat nodeset="customers[1]">
<repeat nodeset="customer">
<output ref="name" />
<output ref="telephone" />
</repeat>
</repeat>
But it's not so the other way round; i.e., saying that elements that use nodesets operate over all of the nodes in the nodeset is actually fairly intuitive, which leads me to wondering whether we should allow this:
<group nodeset="customers/customer">
<output ref="name" />
<output ref="telephone" />
</group>
in addition to this:
<group ref="customers/customer">
<output ref="name" />
<output ref="telephone" />
</group>
and this:
<group ref="customers">
<group nodeset="customer">
<output ref="name" />
<output ref="telephone" />
</group>
</group>
We would obviously keep the @ref format for backwards compatibility, and as a shorthand for selecting the first node. And even more interestingly, it could retain its use for setting context, for example when used in conjunction with @nodeset. For example:
<group ref="customers" nodeset="customer">
<output ref="name" />
<output ref="telephone" />
</group>
