Asymmetrically Yours - XML

The range() function is great for times when you need to define a range which begins and ends with the same element. However, for situations which require more asymmetric ranges, XPointer also offers the range-to() function, which allows link authors greater flexibility when defining ranges.

The range-to() function creates a range beginning with the context node and ending with the location set specified as an argument to the range-to() function. For example, the following XPointer

xpointer(id('67')/cast/range-to(id('67')/director))

defines a range beginning at the opening "cast" element and ending at the closing "director" element.

It's also possible to identify points and ranges within character data - the string-range() function scans a specified location for a match to a user-specified string, and returns a range containing the result. So, the following XPointer

xpointer(string-range(//cast, "Patrick Stewart"))

would return a range enclosing the string "Patrick Stewart" from the "cast" element.

If the XML document above contained more than one "cast" element matching the specified string, the string-range() function would return multiple ranges, one for each match.

It's possible to further constrain the range returned by specifying two additional arguments to the string-range() function - an offset to push forward the starting point of the range, and a length constraint to move back the ending point. So a modification of the XPointer above to

xpointer(string-range(//cast, "Patrick Stewart", 9, 4))

would return a range enclosing the substring "Stew".

The string-range() function ignores embedded elements - which means that a change to the XML document above to read

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

would not affect the XPointer at all.

Since the string-range() function only returns string ranges, it follows that the start and end points of these returned ranges are always character-points, not node-points.

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