An interesting comment showed up on my prior post that seemed worth discussing as part of getting around to talking about what XFDL does for (and with) XForms.
In the last post, I talked about what XForms does and what it doesn't do from the big picture perspective. XForms does seek to standardize the language for the core information processing asset expressed within a form. XForms does not seek to standardize the exact presentation of a user interface. XForms delegates this task to different XML host languages like XHTML or XFDL (or others in the future like, hopefully, VoiceXML). These host languages exist to satisfy different requirements that exist beyond the core information processing requirements, but XForms allow us to design the underlying application once and handle presentment and other orthogonal requirements as the separate issues that they are.
The comment came in saying that one thing XForms doesn't do is allow the URL of a submission to be dynamically calculated. This is a technical limitation that does not affect the big picture of what we're trying to achieve with XForms. The XForms language does contain some technical limitations like this. Many of them are being addressed in XForms 1.1. This issue in particular should be addressed in the very next working draft of XForms 1.1.
However, because we have to deliver products that can be used to build applications now, it sometimes happens that implementations have to lead the standard with custom extensions until the standard comes along and specifies the common way that everyone on the working group agrees is the way the language will express a feature.
In XFDL, we make relatively few changes to XForms because we want our documents to be as conformant as possible. However, this particular issue of a dynamic URL comes up in almost all of the forms applications we have every deployed, so we did not feel we could make our next release of Workplace Forms without some ability to do a dynamic URL on an XForms submission. At the same time, we do like it to be clear to the form author when an extension is being used. As a result, the addition was made using an attribute in the XFDL namespace. This makes it easier to find those bits of our XForms-based documents that will need special attention when trying to get them to interoperate with other XForms implementations.
In the upcoming release of Workplace Forms, you can create XForms-based applications that include a dynamic URL component by using an
xfdl:actionref attribute instead of an
action in the
xforms:submission. The content of
xfdl:actionref is an XPath expression whose result is the node containing the desired URL. Of course, the full power of XForms calculations can be brought to bear on that node to allow dynamic calculation of all or any portion of the final URL.
In XForms 1.1, I am expecting a more general mechanism that will allow the instance data to be used to set not just the URL, but eventually many of the other parameters too.