Полное решение:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:variable name="authors" select="document('author.xml')" />
<xsl:variable name="artworks" select="/artworks/artwork" />
<xsl:key name="byNameForm" match="artworks/artwork"
use="concat(author, '|', form)" />
<xsl:template match="/">
<authors>
<xsl:apply-templates select="$authors/*/author" />
</authors>
</xsl:template>
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()" />
</xsl:copy>
</xsl:template>
<xsl:template match="author">
<author>
<xsl:apply-templates />
<xsl:apply-templates select="$artworks[author=current()/name]" />
</author>
</xsl:template>
<xsl:template match="artworks/artwork" />
<xsl:template match="artworks/artwork[generate-id()=
generate-id(key('byNameForm', concat(author, '|', form))[1])]">
<artworks form="{form}">
<xsl:apply-templates
select="key('byNameForm', concat(author, '|', form))"
mode="form">
<xsl:sort select="date" data-type="number" />
</xsl:apply-templates>
</artworks>
</xsl:template>
<xsl:template match="artworks/artwork" mode="form">
<artwork date="{date}">
<xsl:apply-templates select="title|technique|location" />
</artwork>
</xsl:template>
</xsl:stylesheet>
Введите:
<artworks>
<artwork>
<title>Adoration of the Magi</title>
<author>GHIRLANDAIO, Domenico</author>
<date>1486</date>
<technique>Tempera on wood, diameter: 171 cm</technique>
<location>Galleria degli Uffizi, Florence</location>
<form>painting</form>
<type>religious</type>
</artwork>
<artwork>
<title>Something</title>
<author>AMADEO, Giovanni Antonio</author>
<date>1484</date>
<technique>Marble</technique>
<location>Mars</location>
<form>sculpture</form>
<type>religious</type>
</artwork>
<artwork>
<title>Something2</title>
<author>AMADEO, Giovanni Antonio</author>
<date>1487</date>
<technique>Glue</technique>
<location>New York</location>
<form>sculpture</form>
<type>secular</type>
</artwork>
<artwork>
<title>Something3</title>
<author>AMADEO, Giovanni Antonio</author>
<date>1482</date>
<technique>Some tech</technique>
<location>Mars</location>
<form>paper</form>
<type>religious</type>
</artwork>
</artworks>
И
<authors>
<author>
<name>AMADEO, Giovanni Antonio</name>
<born-died>b. ca. 1447, Pavia, d. 1522, Milano</born-died>
<nationality>Italian</nationality>
<biography>Giovanni Antonio Amadeo was an Italian early
Renaissance sculptor</biography>
</author>
<author>
<name>GHIRLANDAIO, Domenico</name>
<born-died>b. ca. 1447, Pavia, d. 1522, Venice</born-died>
<nationality>Italian</nationality>
<biography>N/A</biography>
</author>
</authors>
Выход:
<authors>
<author>
<name>AMADEO, Giovanni Antonio</name>
<born-died>b. ca. 1447, Pavia, d. 1522, Milano</born-died>
<nationality>Italian</nationality>
<biography>Giovanni Antonio Amadeo was an Italian early
Renaissance sculptor</biography>
<artworks form="sculpture">
<artwork date="1484">
<title>Something</title>
<technique>Marble</technique>
<location>Mars</location>
</artwork>
<artwork date="1487">
<title>Something2</title>
<technique>Glue</technique>
<location>New York</location>
</artwork>
</artworks>
<artworks form="paper">
<artwork date="1482">
<title>Something3</title>
<technique>Some tech</technique>
<location>Mars</location>
</artwork>
</artworks>
</author>
<author>
<name>GHIRLANDAIO, Domenico</name>
<born-died>b. ca. 1447, Pavia, d. 1522, Venice</born-died>
<nationality>Italian</nationality>
<biography>N/A</biography>
<artworks form="painting">
<artwork date="1486">
<title>Adoration of the Magi</title>
<technique>Tempera on wood, diameter: 171 cm</technique>
<location>Galleria degli Uffizi, Florence</location>
</artwork>
</artworks>
</author>
</authors>
Редактировать: Обновлен для обработки обработки автором, так что будут включены даже авторы без каких-либо работ.