XSLT 1.0 multi-passing - xslt

Question

I have the following input xml:
<bookstores>
<store>
<name>Store 1</name>
<books>
<book>
<title>Book 1</title>
<author>Author 1</author>
<year>2000</year>
<price/>
</book>
<book>
<title>Book 2</title>
<author></author>
<year>2001</year>
<price/>
</book>
</books>
</store>
<store>
<name>Store 3</name>
<books>
<book>
<title>Book 1</title>
<year>2012</year>
<price/>
</book>
</books>
</store>
</bookstores>
I need to get all stores that have books with identified authors, so the result should be:
<bookstores>
<store>
<name>Store 1</name>
<books>
<book>
<title>Book 1</title>
<author>Author 1</author>
<year>2000</year>
<price/>
</book>
</books>
</store>
</bookstores>
I tried to use exslt:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:exslt="http://exslt.org/common">
<xsl:output method="xml" indent="yes" encoding="utf-8" />
<xsl:strip-space elements="*" />
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*" />
</xsl:copy>
</xsl:template>
<xsl:template match="/">
<xsl:variable name="firstPass">
<xsl:call-template name="processing" />
</xsl:variable>
<xsl:apply-templates select="exslt:node-set($firstPass)" />
</xsl:template>
<xsl:template name="processing" match="bookstores/store/books/book[author[string()='']]" />
<xsl:template match="bookstores/store/books/book[not(author)]" />
<xsl:template match="bookstores/store[not(books/book)]" />
</xsl:stylesheet>
Filter books with empty Author
Filter books without tag Author
Filter sotres without books with authors
but unfortunately I didn't get how to use it in a right way. How to use exslt with several match templates?

Answer 1

I think you can do it in one pass
<xsl:template match="store[not(books/book[author[normalize-space()]])]"/>
<xsl:template match="book[not(author[normalize-space()])]"/>
that way the complete code is
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:template match="#* | node()">
<xsl:copy>
<xsl:apply-templates select="#* | node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="store[not(books/book[author[normalize-space()]])]"/>
<xsl:template match="book[not(author[normalize-space()])]"/>
</xsl:stylesheet>
and gives the wanted output at https://xsltfiddle.liberty-development.net/3NzcBtk.

Answer 2

Your approach can be simplified to
<xsl:template match="store/books/book[string(author)='']" />
<xsl:template match="store[not(books/book/author)]" />
The first one removes books without an author or with an empty author in one expression. The second one removes stores which either have books without an author or have no books at all, because without a book there can't be an author.