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and-egg situations; this chapter has some forward referencing to concepts. As a result, you
may want to skim through the whole chapter once before reading it in detail.
What Makes Up an XML System?
Every XML system is primarily concerned with processing information that is stored in a
standardized format. It doesn’t matter what the objective of the system is per se. We
talked extensively about the applications of XML in
Chapter 2
and throughout all of the
applications, the underlying assumption for each has been that it is based on an XML
system.
An XML system is composed of three generic parts and one unique part. In nontechnical
terms, they can be expressed as content, structural definition, conformity checking, and
customized application. The first three are the generic parts while the last, customized
application is unique to the objective of the system.
Though we cannot anticipate the entire gamut of unique objectives that your XML system
will achieve, we can help you generate the first three parts of your system, which makes
the construction of the last part of your system less code intensive. Bringing things back
into technical terms, an XML system typically consists of the following:
•
XML Document (content)
•
XML Document Type Definition—DTD (structural definition; this is an optional part)
•
XML Parser (conformity checker)
•
XML Application (uses the output of the Parser to achieve your unique objectives)
Figure 3.1 shows how these interrelate.
