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 10th 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