Match Patterns (Locating Elements)
One critical capability of a stylesheet language is to locate source
elements to be styled. CSS, for example, does this with "selectors."
FOSIs do it with "e-i-c's", elements in context. XSLT does it
with "match patterns" defined by the XML Path Language (XPath) (http://www.w3.org/TR/xpath).
XPath has an extensible string-based syntax
It describes "location paths" between parts of
a document or documents
One inspiration for XPath was the common "path/file"
file system syntax
Two things to remember about XPath expressions:
Pattern matching occurs in a context; XPath expressions and
XSLT elements can change the current context and consequently the nodes which
XPath is inclusive or greedy, it addresses all
matching elements. You must use predicates to refine the set of