An XSLT stylesheet consists of a number of template rules:

template rule = pattern + template

For a given input XML document, the output is obtained as follows:

• the source tree is processed by processing the root node
  (implicitly, the root node of a document is a special document node which has the root element as its only child)

• a single node is processed by:
  1. finding the template rule with the best matching pattern
  2. instantiating its template (creates result fragment + continues processing recursively)

• a node list is processed by processing each node in order and concatenating the results

This cartoon illustrates the processing model.

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