XSLT Transformating XML to XML

Question

I have the problem with xslt. How to exactly use template to build output like this? I get tired already a long time with this, and it is problematic to use a tag xmlns

<?xml version="1.0" encoding="utf-8"?>
<books xmlns="http://example.net/books/1.0" xmlns:a="http://example.net/author/1.0">
    <book>
        <a:author>
            <a:name>John</a:name>
            <a:surname>Applesed</a:surname>
        </a:author>
        <title>Missing opportunity</title>
    </book>
    <book>
        <a:author>
            <a:name>Paul</a:name>
            <a:surname>Morgan</a:surname>
        </a:author>
        <title>Test Book</title>
    </book>
</books>

So far I was able to do something like this:

<?xml version='1.0' ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:b="http://example.net/library/1.0" >
    <xsl:template match="/">
        <books>
            <xsl:for-each select="b:library/b:books/b:book">
                <book>
                    <author>
                        <name>
                            <xsl:value-of select="../../b:authors/b:author/b:name"/>
                        </name>
                        <surname>
                            <xsl:value-of select="../../b:authors/b:author/b:surname"/>
                        </surname>
                    </author>
                    <title>
                        <xsl:value-of select="b:title"/>
                    </title>
                </book>
            </xsl:for-each>
        </books>
    </xsl:template>

</xsl:stylesheet>

Starting file is: This file cannot be edited

<?xml version="1.0" encoding="utf-8"?>
<library xmlns="http://example.net/library/1.0">
    <authors>
        <author id="a1">
            <name>John</name>
            <surname>Applesed</surname>
            <born>1979-11-11</born>
        </author>
        <author id="a2">
            <name>Chris</name>
            <surname>Pattern</surname>
            <born>1965-12-12</born>
        </author>
        <author id="a3">
            <name>Paulo</name>
            <surname>Coelho</surname>
            <born>1915-06-17</born>
        </author>
        <author id="a4">
            <name>Paul</name>
            <surname>Morgan</surname>
            <born>1473-02-19</born>
            <died>1543-05-24</died>
        </author>
    </authors>
    <books>
        <book id="b1" author-id="a1">
            <title>Missing opportunity</title>
            <published>1992</published>
            <isbn>978-3-16-148410-0</isbn>
        </book>
        <book id="b2" author-id="a4">
            <title>Test Book</title>
            <published>1543</published>
        </book>
    </books>
</library>

Answer 1

Try it this way:

XSLT1.0

<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
xmlns:b="http://example.net/library/1.0" 
xmlns:a="http://example.net/author/1.0"
exclude-result-prefixes="b">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:strip-space elements="*"/>

<xsl:key name="author" match="b:author" use="@id" />

<xsl:template match="/b:library">
    <books xmlns="http://example.net/books/1.0">
        <xsl:for-each select="b:books/b:book">  
            <xsl:variable name="author" select="key('author', @author-id)" />
            <book>
                <a:author>
                    <a:name>
                        <xsl:value-of select="$author/b:name"/>
                    </a:name>
                    <a:surname>
                        <xsl:value-of select="$author/b:surname"/>
                    </a:surname>
                </a:author>
                <title>
                    <xsl:value-of select="b:title"/>
                </title>
            </book> 
        </xsl:for-each>
    </books>
</xsl:template>

</xsl:stylesheet>

---

Note the use of a key to resolve the cross-references to authors. This has nothing to do with the namespace issues, but it's more efficient this way.

Answer 2

You are not constraining your authors when preparing output records. Also ../.. are useless in this context. Use something like this

<xsl:value-of select="//b:authors[@id = ./@author-id ]/b:author/b:name"/>