For well over a year now, the Interactive University Project -- and I, in particular, have been involved in translating various XML-based formats to other formats.  How did we ever get into such a line of work?  It basically all started when we at the IU were shown the scrapbook of Yoshiko Uchida digitized by the Bancroft Library.  Uchida was within within a few weeks of her graduation from UC Berkeley, when in 1942, she and her family were sent to an internment camp.  (I think that I got this part of her story right.)  The scrapbook is a moving record of her experience, a composite of newspaper clippings, cards, correspondence and other personal effects.  The UC Berkeley library digitized the scrapbook and encoded it in the MOA2 format, an XML format for encoding digital objects. 

We at the IU were immediately impressed by not only the technical quality of the digital material but its stunning educational potential.  Not only did the library at Berkeley have a treasure trove of documents like the Uchida scrapbook that have already been digitized or were waiting digitization, but the library was also encoding these documents in a standard XML format, the MOA2 format, which later evolved into METS.  Because the IU is in the business of opening up the resources of the campus to the public, especially to K-12 teachers, we saw that the encoding of large quantities of high quality research content was a huge boon to the public for the following reasons:

• That digital documents were not only encoded in XML  and that this XML source document was available to the public makes it much easier for others to create new and multiple representations and interpretations of the document as a whole or in part. (Though the XML markup of the documents was done primarily to make the exchange and handling of these documents easier for the housing instittutions such as libraries, musuems, and archives, a beneficial side effect is that the markup is also available for other uses by those outside the library and museum community.)
• The adoption of METS by a significant number of libraries, musuems, and archives to mark up their content would result in many thousands of interesting, high quality content in a common format, which in turn, encourages the development of tools.
•  The markup of archival objects documents clearly the relationships among the parts in a complex object and their attendant metadata..  Such clear inidcators makes for more intelligent disaggregation and reaggregation of objects.
  

As exciting as METS was (and still is), we did note that many of the tools that our users want to use would not be able to handle METS -- and may never be programmed to do so.  This inability to deal with METS directly is not surprising since METS comes from the digital library community, a relatively specialized field.  Though these other tools do not handle METS, many of them do handle other XML formats, which are standards or emerging standards in their respective communities.  Before discovering METS, we had been tracking the emergence of weblogging tools, in which content was being shared (syndicated) through RSS, another XML format.   Weblogs were on the IU's radar screen  because they were facilitating a great deal of writing on the Web, writing that often drew upon the content of the Web. 

We were intrigued by the educational promise of weblogs and wanted to see how one can blend writing with the deep content coming from libraries.  A first step in such blending would be to import content into weblogging tools.  To do so, one would have to translate content encoded in METS to RSS and then import the resulting RSS into the weblog.  I wrote XSLT to perform that crosswalk and converted METS objects into RSS. 

Once we figured that trick, we saw that there were a number of other formats into which it would be useful to convert.  On college campuses, an increasing amount of instruction is being mediated through "learning management systems" (LMS).  There have been significant efforts to define XML specifications to ensure interoperability among educational environments.  Notable among them are specifications developed under the auspices of the IMS, specifically the IMS-Content Packaging and IMS-MD specifications (for the packaging and labeling of educational content, respectively). Since we were very interested in enabling faculty and students make use of digital content coming from the libraries in instructional contexts, we started looking into writing crosswalks from METS to IMS-Content Packaging.

That's how we got started on the long road to writing crosswalks....