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.
What is the value proposition of an open standard?
XML is fairly pervasive, so we rarely ask this question of XML anymore, but once upon a time the question came up a lot as business managers tried to figure out why the technical people were insisting on spending money to move to XML. And the truth is that the impact is difficult to measure precisely, so open standards are sometimes a bit of an uphill battle. Nevertheless, the software engineering benefits are tangible and increase in magnitude over time.
One benefit is, of course, the human resource factor. Given a schema or DTD for a pile of pointy brackets, human beings can learn a lot about your document format quickly, which means they can become proficient more quickly and be more efficient overall at moving information into and out of the document.
This has an impact on the development of software systems. The software engineering benefits of increased interoperability/looser coupling of system modules have a significant positive effect on the time and cost efficiency of software development. Really, it's the same benefits as a service oriented architecture, which is why SOA and XML documents are such a good match.
But XML standardization has a deeper impact as it also places a value on the document format. In other words, the document format becomes a product in and of itself. A software system based on an XML document format is more valuable than one that is not because it is easier for enterprises to migrate to or from the document format. The benefit to a vendor of enterprises being able to migrate to the vendor's format is immediately obvious, but the ability of the enterprise to migrate from the vendor's format is also surprisingly valuable to the vendor. This is true not just for the obvious reason that being trapped in a document format is inherently costly to an enterprise. So, the enterprise can more readily adopt a vendor's solution when it does not imply vendor lock-in, but frankly it is the capability to more easily migrate away from the vendor's solution that becomes a selling point. A vendor can say, "We know you have a choice, so we're going to be responsive to your needs and deliver quality software so you keep choosing us."
It is with all these benefits in mind that we moved the predecessor of Workplace Forms to an XML syntax called XFDL. The XFDL language is an XML vocabulary that simplifies the design, development and deployment of high precision, secure forms applications that provide a rich user experience.
Of course, the first thing we did with our new XML syntax was to report it to the W3C in a document which became a W3C Note. The purpose of a W3C Note is to bring to the attention of the W3C something that contains aspects worth of consideration for standardization. The W3C does not and never will standardize a vendor's submission. But it does take note of its own notes! A positively reviewed note is likely to result in some movement in the standardization world. In the case of XFDL, that movement has occurred all over the place, including the likes of XPath, XML Schema, XML Signatures and Canonicalization, and XForms.
Of course, XFDL now incorporates XForms to express all aspects of XFDL that it can. And like a good standard ought to do, XForms itself incorporates other W3C technologies where appropriate, like XPath and XML Schema. But XForms depends on a host language to deliver the actual user experience, and there are aspects of a precision presentation and rich user experience that properly belong at the host language level. And XFDL even encodes these bits with the most pervasive standard of all -- XML.
I am the happy owner of an excellent new book entitled "Document Engineering" by Robert Glushko and Tim McGrath. The reader goes on journey through many of the XML technologies that are brought to bear to solve business informatics problems. The journey does not jostle and stab with so many pointy brackets, but rather focuses intently on why we need all of these technologies and how to put them together sensibly.
There are so many nuggets of wisdom in the book that of course I cannot tell you all about it in this blog. Just like the Matrix, you have to see it for yourself! But I would be remiss in not giving you at least a taste, especially since the message is so closely aligned to the value proposition of XForms and, indeed, XFDL+XForms.
- Documents describe the interfaces to business processes. (Ch. 1)
- Loose coupling is necessary for integration across enterprise boundaries... (Ch. 4)
- Service oriented architecture is a design philosophy; web services are a set of standards and techniques. (Ch. 4)
In other words, XML documents are the lifeblood of a service oriented architecture, and XML technologies are valuable because they help us overcome the limitations of rigid, monolithic systems.
With Workplace Forms, we combine XFDL and XForms to achieve a somewhat elaborated version of this view in which the forms themselves are the documents that make their way through a service oriented architecture, interacting according to their own rules of engagement to achieve validity of the contained XML data document and more efficiently achieve the intent of a business process.
In other words, the SOA is the infrastructure, the XFDL form is the medium, and the XML data is the message. With this analogy, it is easy to see that the powerful words of Marshall McLuhan are applicable: The medium is the message. The more powerful the medium, the more powerful the message. An XForms layer around XML data trumps a system in which only the XML data is standardized. An XFDL layer around the XForm... transaction auditability, digital signature security, comprehensive accessibility, rich text, globalization, and on and on. All the things we get to talk about in future installments of this blog.
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.
The purpose of XForms is to express the core XML data processing asset used in sophisticated data collection scenarios.
In fact, it would be better if XForms were called the XML data processing language (XDP or XDPL) because XML is about standardizing data and about 80% of business transactions are based on filling out some kind of form to collect the transactional data.
An XForm contains one or more XML data instances. An instance is an arbitrarily structured XML data document that is typically an instance of some XML schema that expresses the static validation rules for a target namespace.
One can write an XForm without an XML schema by just expressing the XML data in an instance. This is because XForms provides other channels of data validity checking that can be easier to work with when only simple data type validation is needed. For example, you can use an XForms
type declaration to associate an
xsd:date or similar data type to an XML data node without writing an XML schema for your XForm.
But XForms validity checking is also dynamic, in recognition of the fact that validity of some values can be based on other values or the aggregation of other values. For example, in an interlibrary article request, the upper bound page number in the journal must not be less than the lower bound page number. Or, the user is only authorized to make a purchase order with less than $10,000 total value.
The latter example is important because it leads to the conclusion that we not only need a way of testing data values relative to other data values, but also that we need a way of calculating data values that are then used in validity tests.
From there, it is not a big leap to conclude that generalized XML data processing requires some way to indicate dynamically whether further changes should be allowed to certain pieces of data or whether certain parts of the data are still applicable to the transaction based on other data values. A good example is a mortgage preapproval form that can handle both single and joint applications. The co-applicant data is only relevant if the user selects the joint application mode.
XForms allows the form author to express formulae for these aspects of data, which are called model item properties, or just MIPs. Not too surprisingly, the names of these MIPs are
Of course, there is no point in representing data, calculating values over data, and validating data if you have no way to change the data. XForms allows simple content data values to be changed, but it also allows insertion and deletion of larger blocks of data that contain internal structure because this is essentially what's needed to add or delete a row from a table.
Most importantly, XForms offers form controls that expose data to the surrounding application context. If the data changes, the form controls change. This includes not only exposing a changed simple content data value, but if a set of form controls are associated with a repeated sequence of structured data, and the number of data nodes in the sequence changes, then form controls are created or destroyed as needed to respond to the change of data.
XForms is all about thinking of the data first and driving outward to how that data gets exposed to applications. Perhaps the most prevalent of such applications are for presenting the data to a human user, though even human users have highly varied capabilities. For example, the desktop user and the PDA user have very different visual capabilities. Of course, this argument extends easily to meeting the far greater accessibility needs of the sight-impaired.
For this reason, the XForms form controls represent what I've often called an intent-based user interface. It's kind of neat to see the term popping up more frequently now. It gets to the heart of the matter: XForms does not provide a presentation layer. XForms relies for presentation on a host language like XFDL (in Workplace Forms) or XHTML (in web browsers). I am certainly hoping that VoiceXML will come to the conclusion that they should soak up the benefits of XForms rather than reinventing all of this stuff over again (partly because almost everybody underestimates how much work goes into it until it's too late; but maybe they will prove to be wiser than the rest).
I sometimes get asked whether XForms will next extend itself to standardizing the actual presentation layer. Clearly, from above the answer is no. XForms standardizes the core XML data processing asset, and more work will go into doing a better job of that. The key issue we want is to address interoperability and reusability across applications and user contexts of the data processing behaviors that are fundamental to completing a transaction.
The powers that be asked the dW bloggers to help spread the word about the download availability today of DB2 Viper Release Candidate 1.
Please see www.ibm.com/db2/viper
You can also get more info from
Anyway, why does this make sense on a blog about Workplace Forms?
As I said before in this blog, the purpose of a form is to collect data. If you want to collect data about a pizza order, you don't want us, but obviously there are more sophisticated information needs than that, right!
Question is, once you've got the data, what do you do with it?
There's always a server side to any web application. Products like DB2, Content Manager, and Portal Document Manager are about providing high strength persistence tiers for the consumption of data collected across an enterprise or across enterprises. Products like WebSphere Application Server and WebSphere Portal Server are about creating that middle layer that creates the logical bridge between from the point where you have the data to the point where you know what to do with it (something has to decide where to put the data, what data to retrieve, etc.).
And IBM Workplace Forms is there to put a beautiful face on it all by intelligently collecting data of any level of complexity while providing a richly textured user experience. And DB2 Viper is an especially good fit with IBM Workplace Forms because our forms contain XForms, which is a pure XML play, and the most significant addition to DB2 in Viper is the native-XML data model.
IBM is interested in all manner of open standards, including XForms, because they allow organizations to express their information assets in a format that can more easily be preserved as one incorporates more technologies into an application over time to meet evolving business requirements.
As Kevin Kelley (STSM, emerging standards) explained in a telecon this morning, the standards are like an on-ramp that allows assets to be developed over time. If you care about reuse of those assets, then you care about standards.
To be honest, this is the same argument that drove XML to the ubiquity it currently enjoys. With XML, we sought to standardize how data models are expressed. With XForms, we seek to standardize the expression of processing models over that data.
Some upcoming posts:
1) What does XForms actually offer?
2) How does XFDL fit into the above open standards story?
3) What makes XFDL+XForms an ideal format for archival, transaction auditabilty, and transaction security purposes?
Continuing from the last post, here is a reasonable use case for having a global (namespace qualified) attribute with the same local name as a local (unqualified) attribute, where the attributes do not have the same meaning and the global attribute is in the same namespace as the containing element.
The current version of XML Events allows you to declare a listener for an event on a node. There are multiple ways to do this, but the easiest is to use a global attribute in the events namespace (signified by the prefix ev below):
<xforms:action ev:event="DOMActivate"> ...
An xforms:trigger can be represented, for example, by a button widget, and pressing the button results in a DOMActivate event on the trigger.
The ev:event declares the name of the event to listen for, and the default value for ev:target (when it's not specified) is the parent
element of the one containing the ev:event. So, the above declaration causes a listener to be created for the occurrence of the DOMActivate on the trigger. The handler for the event is given by the content of the xforms:action that bears the ev:event. An example of an action to be performed would be inserting a node of data (which would likely correspond to adding a row to a repeat table).
All of this is just plain vanilla XForms so far. But at the W3C tech plenary, the XHTML working group began discussing upgrades to XML events. The reason is that the current version of XML events declares listeners that are created at the moment when the DOM node being listened to is created. There's no way to create a listener later in the life time of a document, possibly contingent on some condition or the occurrence of some event.
Syntax for this could
look something like this:
target="X" event="Y" ...
In this example, ev:listener is an action handler for the DOMActivate event that happens on the trigger. So when you activate the trigger (press the button), a listener for event Y is created on the node with id="X".
The local, namespace unqualified attribute 'event' tells the event that the listener will listen for. The global, namespace qualified event 'ev:event' tells the event whose occurrence causes the ev:listener action to be performed.
This is a very neat and compelling example where a local attribute (event) which is given meaning by a namespace (XML Events) might legitimately have a completely different meaning than a global attribute with the same local name and same namespace as the containing element (ev:event).
Although the XHTML working group quite liked this solution, they had a lengthy discussiona and concluded that this aspect of XML namespaces is not understood well enough to rely on the feature without confusing document authors. Of course, they are free to change their minds later, I would say that the above syntax is not likely to see the light of day in a W3C recommendation.
That's why I'm blogging it. Because even if it goes away, we still need to try to increase understanding of this aspect of namespaces and attributes, and nothing does that better than a good example, and this is the first one I've seen.
And we can thank Steven Pemberton for it![Read More
Well, no blogs from me next week, so seems a good idea to knock off another one this week...
XML namespaces rec (pardon the pun) states that an attribute which is namespace unqualified
is 'local' to an element and is uniquely identified by a combination of the attribute local name and the type and namespace URI of the containing element.
The word identify
really should be used more sparingly, as here is a case where its misuse has caused years of confusion and acrimony in the XML community. An identifier is something that established the identity of something else. You cannot have two things associated with the same identifier unless they are identical things.
I am often frustrated by seasoned W3C folks who say that "this depends on your definition of identify" and honestly
believe this is a defense of the confusion in the namespaces rec. This is like saying ot me, "Well you're right unless you have a definition for identify that doesn't identify things, which is what we
did at the W3C."
To see the problem, you have to look earlier in the spec where a namespace n1 is associated with a URI and then the following code appears:
<good a="1" n1:a="2" />
The problem is that the element 'good' is in the same namespace as n1. So now you have local attribute a
that is essentially given meaning by an element that is in the same namespaces as the 'global' attribute n1:a
. Yes the two attributes have different values.
From this we have to infer that, although a local attribute is given meaning based on the containing element and its namespace, a global attribute with the same local name and namespace qualified into the same namespace can actually mean something totally different.
In other words, we have two attributes with the same local name, contained by the same element, and given meaning by the same namespace URI, but they are not identical. This is the local attribute not
being 'identified' (in my sense) by local name and containing element type and namespace.
The technically subtle W3Cer will tell you that there was no reason to spell out using words in the normative part of the spec the fact that the two attributes are different things because the spec says that local attributes are in a different partition than global ones. Problem is, this partitioning info is in a non-normative part of the spec, and particularly in the same part that has the language about how local attributes are 'identified' by local name and containing element type and namespace.
Anyway, the upshot is that an XML vocabulary does not need to but is allowed to say that local and global attributes with the same local name can mean different things. If they're supposed to mean the same thing, then the XML language has to define a precedence rule for what happens if the two attributes differ in value. Here's an example:
<data xmlns="http://example.org" xmlns:ex="http://example.org">
<price currency="USD" ex:currency="EUR">10</price>
Question: Is the price in USD or Euros?
Answer: Depends on who designed the language.
Second answer: Don't do that.
Interestingly, the XHTML working group came up with a fascinating example where it is legitimate and sensible to have a global and local attribute with the same local name but completely different meanings. It has to do with the next version of XML events. After hours of discussion, the decision was that they weren't going to do that (second answer above). Not because it's illegal, but because it's too subtle for most XML people.
Well, the XHTML group may change their minds, but even if they don't, the example is really worth understanding because it actually makes sense why you'd want to have the two attributes mean something different. Stay tuned, I'll tell you all about it when I get back...[Read More
XForms 1.0 Second Edition has been published today at http://www.w3.org/TR/xforms/
To get an idea of the quality and quantity of improvements made to XForms, please see http://www.w3.org/2003/10/REC-xforms-10-20031014-errata.html
Based on this improved foundation, the XForms working group will now be focusing its energies on the completion of XForms 1.1. To get an idea of what will be available, check here: http://www.w3.org/TR/xforms11/
The one comment I would make about the above working draft is that the we will almost certainly revert to using the same namespace currently used for XForms 1.0, and instead use some mechanism within
the language to do versioning.
In keeping with my prior post about signatures and namespaces, it is important to version a language either internally or by updating the namespace URI. Previously, we chose the namespace route because XForms is designed to be hosted within another language, so it has no root element of its own to which a version could be attached.
However, XForms 1.1 is using some special schema wizardry that allows it to have a "chameleon" namespace, which will make it easier to import XForms into a host language like XHTML without namespace qualification. I'm not a big fan of doing this, especially for host languages other than XHTML because it becomes harder to find the XForms within another document and host the XForms functionality separately from the original host language.
Nonetheless, the feature is there and it occurred to me during the W3C tech plenary that the chameleon namespace could be used to put XForms 1.1 back into the XForms 1.0 namespace. That means that XForms processors trying to determine what semantics to attach to the vocabulary need some other way
to make their decisions. So we simply have to solve the versioning problem without using a change of namespace URI.
The camp that wanted us not to change namespaces will be happy. My own XSLTs will be happy too.[Read More