xml - 在 XSL 中，如何根据多个属性选择一个值？

Question

这一定是一个非常基本的问题，但我真的很难找到解决方案。当我在 tag="099" 和 code="a" 属性上匹配时，我试图从以下 XML 中提取第一个实例分别在 marc:datafield 节点和 marc:subfield 节点

<?xml version="1.0" encoding="UTF-8" ?>
<marc:collection xmlns:marc="http://www.loc.gov/MARC21/slim"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.loc.gov/MARC21/slim http://www.loc.gov/standards/marcxml/schema/MARC21slim.xsd">
<marc:record>
    ...
    <marc:datafield tag="079" ind1=" " ind2=" ">
        <marc:subfield code="a">79927839</marc:subfield>
    </marc:datafield>
    <marc:datafield tag="099" ind1=" " ind2=" ">
        <marc:subfield code="a">940002</marc:subfield>
    </marc:datafield>
    <marc:datafield tag="099" ind1=" " ind2=" ">
        <marc:subfield code="a">940002*</marc:subfield>
    </marc:datafield>
    <marc:datafield tag="099" ind1=" " ind2=" ">
        <marc:subfield code="a">940002**</marc:subfield>
...        

所以，我正在尝试检索第一个“940002”。使用以下代码:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs"
version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/"
xmlns:marc="http://www.loc.gov/MARC21/slim">
<xsl:output method="xml" encoding="UTF-8" indent="yes"/>
<xsl:template match="/">
    <record xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/">
        <!--identifier-->
        <xsl:if test="/marc:collection/marc:record/marc:datafield/@tag='099'">
            <xsl:element name="dc:identifier">
                <xsl:if test="position()=1">
                    <xsl:value-of select="/marc:collection/marc:record/marc:datafield/marc:subfield/@code='a'"/>
                </xsl:if>
            </xsl:element>
        </xsl:if>
...

但是，我得到的是:

<?xml version="1.0" encoding="UTF-8"?>
<record xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:dcterms="http://purl.org/dc/terms/"
    xmlns:marc="http://www.loc.gov/MARC21/slim">
   <dc:identifier>true</dc:identifier>
   ...

而不是想要的:

       <?xml version="1.0" encoding="UTF-8"?>
<record xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:dcterms="http://purl.org/dc/terms/"
    xmlns:marc="http://www.loc.gov/MARC21/slim">
   <dc:identifier>940002</dc:identifier>
   ...

我猜这一定是 Xpath 问题，但是...任何线索都将不胜感激。

谢谢

Answer 1

使用:

/marc:collection/marc:record/marc:datafield
                   [@tag='099']/marc:subfield[@code='a'][1]/text()