The advantage of a standardised, structured data format is not limited to data exchange with other systems that understand the same format. Some cool work with XSLT by Raymond Yee and also the Digital University (DU) of the Netherlands demonstrates that content in one standard format can be transformed into another in practice.
The DU's challenge was to take existing content in EML (Educational Modelling Language, the predecesor to IMS Learning Design), and extract the questions out of it for use in the Blackboard VLE. Except Blackboard doesn't understand EML. And EML isn't even an XML application - the standard structured data format of most recent educational interoperability standards.
Still, EML shares a parent with XML: Standard Generalized Markup Language (SGML). So step one was to transform EML into something that looks more like XML. Not easy, but the DU team did this with some specialised software.
Once in XML format, the question was whether to go straight to Blackboard's proprietary question format, or use IMS Question and Test Interoperability (QTI). Blackboard's format is not a good idea, because it would require custom programming, and even then it would only work in either version 5 or 6, but not both. Never mind other VLEs or specialised question and test software.
Fortunately, Blackboard purports to read QTI. Unfortunately, it doesn't actually work very well. Fortunately, you can get QTI into Blackboard via a third party product, Respondus, which was chosen for the job.
The real magic here is in the means of transforming one XML format to another. If you want to, you can do that in any computer language that you happen to know- XML is just text, after all. The program then needs to recognise the right bits in the source XML and convert them into something else. Which can be rather a job.
The proper way, really, is via eXtensible Stylesheet Language Transformations (XSLT). This W3C language is specifically intended to transform one XML application to another; much easier to program, much more flexible and independent of a specific computer system set-up.
The DU team claims that the end result actually works quite well. The only real gotcha was a lack of ordering in the that Respondus doesn't really know what to do with the QTI 'section' element.
Raymond Yee's effort is a veritable switchboard of xml standards. Using the webservices offered by Amazon as a basis, you can turn any set of Amazon search results or your wish list into any one of the following: RSS (the content syndication format popular with bloggers), METS (Metadata Encoding and Transmission Standard), good old HTML, and IMS CP (Content Packaging).
For most elearning purposes, the transforms from METS to IMS CP is the more interesting. IMS CP is simply the standard to wrap up and exchange learning objects- SCORM uses it, for example. METS is a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, and is widely used in the library world. Hence making objects from a library available for inclusion in a learning object, or storing a learning object in a digital library could be much easier with Raymond's transform. And since it's all done in XSLT, you can either make use of an XSLT service like the W3C's, or use the stylesheet itself in any number of tools.
The thing to bear in mind, though, is that it isn't magic. If one XML format has an element that just doesn't have a corresponding element in another format, some hackery is called for. Either you'd have to extend the target XML instance (which requires careeful planning, and some consensus), or just drop it.
The wider implication of such XSLT technology, though, is that it demonstrates that as long as you have your stuff in one open, preferably XML defined standard, making it available in another open XML standard is quite doable. All of these formats were developed for different purposes and independent of each other, but since they're structured properly, and since it is known what each element means, they can still interoperate.
There's more on the DU's work with EML and QTI on the Open University of the Netherlands' Learning Networks site.
Raymond Yee's excellent transformers are gathered on hisWebnet talk page.