We usually think of a document as a file. A file is, at the operating system level, a unit of information. The OS can associate properties with it (like who can read it or write it), and the file can easily be moved from directory to directory or computer to computer with standard tools like FTP, email, or flash drive.
The XML recommendation defines a document as that which conforms to BNF rule #1 of the XML syntax. Of course it is useful if an XML document is the sole content of the unit of information being transferred, i.e. if the XML is the only thing in a file. This is because XML tools tend to be built with programming languages that expose services of the operating system.
However, the most important part of an XML document is capable of being contained within another document. In fact, XML canonicalization strips away the part of an XML document that would prevent the result from appearing as element content.
This is the idea that XForms uses when it expresses XML instance data within a larger document, and specifically within the
<xforms:instance> element. Of course, the
<xforms:instance> element can also reference a whole XML document using the
src attribute, but in both cases, the result is parsed into the live running instance data. The user interacts with the XML data document, and the XML data document is what is returned to the server by an
This paradigm works well enough if you think of a form as an ephemeral view of a back-end database or content repository. However, people find it easier to work with a document in the file sense of the word. we like to save our document, email it, reload it the next day or on a new computer, and especially on a computer that has become disconnected from the net or from the original web application context that would be associated with the ephemeral view kind of form.
Enter the document-centric approach of Workplace Forms, the technological basis of which is an XML document whose element names belong to the XFDL and XForms vocabularies. Moreover, the underlying XML data document is still incorporated by the
<xforms:instance> just like all other XForms-based documents.
A key difference is that being a document implies that the form with eventually have to be re-serialized, e.g. to save or sign the form. XForms doesn't really talk about how to reintegrate the live, modified XML data back into the document, but in truth it's really not that hard. The main technical hiccup on the XForms side is that the
src attribute takes precedence over the content of
<xforms:instance>, so when the live data is synchronized back into the form, the
src attribute has to be eliminated.
The conclusion, though, is that a Workplace Form, or XFDL document, is a cross between an office document and an mobile intelligent agent. It can be saved, reloaded, printed, emailed, archived, signed, submitted to web application and portal servers, and participate in document management, records management and content repository processes. This is how the notion of document makes a form be more than just an ephemeral view of data.[Read More]