What do two sets of square brackets (like a 2D array) mean in XPath?
position, syntax, xml, xpath
Solution
The predicates operate in a context. When you use `//bookstore/book[3]` (which is equivalent to `//bookstore/book[position()=3]`) you are restricting the node-set to the matching node in the third position. In that context if you add an extra predicate like `[1]` you are simply selecting the one and only node available.
This is useful if your first predicate results in a node-set which you wish to add more restrictions with another predicate. For example, if your first predicate had restricted the nodes by selecting the year
//bookstore/book[year=2005]
you would have two nodes, and you could select the first one of those 2 with a second predicate, selecting the position:
//bookstore/book[year=2005][1]
You can add any number of [1]s after you have only one node, since it the result will always a node-set containing one node, and you are selecting the one in the first position:
//bookstore/book[3][1][1][1][1][1][1]
Problem
In XPath, what does it mean when you write a query that includes two consecutive values enclosed in `[]`, like a Java array `[][]` For example: ``` //bookstore/book[3][1] ``` When I do this, I get the 3rd book as the result (the same if I would have just said `//bookstore/book[3]` I've been trying to play with this and determine what exactly is happening, for example, I tried `//bookstore/book[3][2]` and `//bookstore/book[3][0]` but got no results. It seems to only work if the second value is `1` but I have no clue why. Here is the XML I'm playing with: ``` <?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book category="COOKING"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book> <book category="CHILDREN"> <title lang="en">Harry Potter</title> <author>J. K. Rowling</author> <year>2005</year> <price>29.99</price> </book> <book category="WEB"> <title lang="en">XQuery Kick Start</title> <author>James McGovern</author> <author>Per Bothner</author> <author>Kurt Cagle</author> <author>James Linn</author> <author>Vaidyanathan Nagarajan</author> <year>2003</year> <price>49.99</price> </book> <book category="WEB"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book> <book category="OPENSOURCE"> <title lang="en">Open Source</title> <year>2003</year> <price>39.95</price> </book> </bookstore> ```