Proof Of The Pudding - XML

By combining the axis and node test into a location step, and combining multiple location steps into a location path, it becomes possible to locate specific nodes with the document tree quite easily. Using the following XML sample, let's consider some examples.

<?xml version="1.0"?>
<movie id="67" genre="sci-fi">
<title>X-Men</title>
<cast>Hugh 
Jackman, Patrick Stewart and Ian McKellen</cast>
<director>Bryan Singer</director>
<year>2000</year>
<?play_trailer?>
</movie>

The path

/child::movie/child::cast/child::text()

references the text node

Hugh Jackman, Patrick Stewart and Ian McKellen

In order to make this a little easier to read (and write), XPath assumes a default axis of "child" if none is specified - which means that I could also write the above path as

/movie/cast/text()

The * character matches all child elements of the context node, while the @ prefix indicates that attributes, rather than elements, are to be matched. The path

/movie/*

would match all the children of the "movie" element, while the path

/movie/@*

would refer to all the attributes of the movie element. In case I need a specific attribute - say, "genre", I could use the path

/movie/@genre

or the path

/movie/attribute::genre

both of which would reference the value

sci-fi

Finally, the path

/*

would reference the first element under the document root, which also happens to be the outermost element, while the path

//*

selects all the elements in the document.

So far as constructing basic XPointers go, the material above is more than sufficient for your needs. However, if you'd like to learn more about XPath's capabilities, including its built-in functions and expressions, take a look at the XPath tutorial  at the XPath specification at http://www.w3.org/TR/xpath.html.

>>> More XML Articles          >>> More By icarus, (c) Melonfire

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