practice

Doi: 10.1145/1364782.1364795

Don’t let delusions about XML develop into a virulent strain of XML fever.

BY eRiK WiLDe anD RoBeRt J. GLuShKo
XmL
fever

THE ExTENSIBLE MARKUP LANGUAGE (xML), which just celebrated its 10^th birthday, ⁴ is one of the big success stories of the Web. Apart from basic Web technologies (uris, http, and htMl) and the advanced scripting driving the Web 2.0 wave, XMl is by far the most successful and ubiquitous Web technology. With great power, however, comes great responsibility, so while XMl’s success is well earned as the first truly universal standard for structured data, it must now deal with numerous problems that have grown up around it. these are not entirely the fault of XMl itself, but instead can be attributed to exaggerated claims and ideas of what XMl is and what it can do.

This article is about the lessons gleaned from learning XML, from teaching XML, from dealing with overly optimistic assumptions about XML’s powers, and from helping XML users in the real world recover from these misconceptions. Shamelessly copying Alex Bell’s “Death by UML Fever,” 1 we frame our observations and the root of the problems along with possible cures in terms of different categories and strains of “XML fever.” We didn’t invent this term, but it embodies many interesting metaphors for understanding the use and abuse of XML, including disease symptoms, infection methods, immunization and preventive measures, and various remedies for treating those suffering from different strains.

XML fever can be acquired in many different ways, but the most prevalent way is to be infected by the idea that XML enables almost magical universal interoperability of information producers and consumers. XML fevers can be classified as basic, intermediate, and advanced:

Basic strains infect XML neophytes, but most of them recover quickly. It can be disappointing to discover that the landscape of XML technologies is not as simple as expected, and that working with the associated tools requires some getting used to, but most people develop some immunity to the XML hype and quickly begin to do useful work with it.

Intermediate strains of XML fever are contracted when XML users move beyond simple applications involving structured information and encounter models of data, documents, or processes. A recurring symptom in these varieties of XML fever is mild paralysis brought on by having to select a schema language to encode a model, trying to choose among the bewildering number of features in some languages, or trying to “round-trip” a model between different environments.

Advanced strains of XML fever often take hold after exposure to the proliferation of more complex and esoteric XML-based technologies layered on top of it. These advanced diseases are