CODEWITHSUNDEEP
xmlxpathxquery
user1696230
user1696230

Reputation:

Using XPath with more than one XML file

I am trying to write an XPath query to find the locations of authors of papers which were published in 2008. I have two files, authors.xml and papers.xml. I have added a fragment of each file below to illustrate the structures of each.

How do I write an XPath query that gets information from both files? I have written a query to get the locations of each author, but I do not know how to extend this to limit the results to authors who published in 2008.

My current XPath query:

doc("authors.xml")//author/location

Current output (locations of all authors):

<location>Berkeley</location>
<location>Stanford</location>

Desired output (locations of only authors who published in 2008):

<location>Berkeley</location>

authors.xml:

<authorRoot>
    <author>
        <first>John</first>
        <last>Doe</last>
        <location>Berkeley</location>
    </author>
    <author>
        <first>Don</first>
        <last>Knuth</last>
        <location>Stanford</location>
    </author>
</authorRoot>

papers.xml:

<paperRoot>
    <paper>
        <journal>
            <author>Don Knuth</author>
            <title>TeX for fun</title>
            <year>1995</year>
        </journal>
    </paper>
    <paper>
        <book>
            <author>Jack Daniels</author>
            <title>The Ballmer Peak</title>
            <year>2004</year>
        </book>
    </paper>
    <paper>
        <journal>
            <author>John Doe</author>
            <title>P equals NP</title>
            <year>2008</year>
        </journal>
    </paper>
</paperRoot>

Upvotes: 1

Views: 97

Answers (1)

bjimba
bjimba

Reputation: 928

Well, now that we've established XPath 2.0, we can use a for statement.

for $a in doc('authors.xml')/*/author 
    return
    if (doc('papers.xml')
    /*/paper/*[author = concat($a/first, ' ', $a/last)]
    /year[. = '2008'])
    then $a/location else ()

This could all be on one line, but please don't do so. If whitespace is allowed, use it for readability.

Upvotes: 0

Related Questions