我有这样的 XML
<?xml version="1.0" encoding="utf-8"?>
<?xml-stylesheet type="text/xsl" href="do.xsl"?>
<catalog>
  <cd>
    <title_>Empire Burlesque</title_>
    <artist>Bobby</artist>
    <company>Columbia</company>
  </cd>
  <cd>
    <title_>Shirt2</title_>
    <artist>Bobby</artist>
    <company>Columbia2</company>
  </cd>
  <cd>
    <title_>Fingers</title_>
    <artist>Bobby</artist>
    <company>Columbia3</company>
  </cd>
  <cd>
    <title_>Zip1</title_>
    <artist>Bobby</artist>
    <company>---</company>
  </cd>
  <cd>
    <title_>Zip2</title_>
    <artist>Bobby</artist>
    <company>---</company>
  </cd>
</catalog>
我需要用以前有意义的数据替换 --- Columbia3 我接下来要做
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" version="4.0" encoding="utf-8" indent="yes"/>
<xsl:template match="/">
  <html>
  <body>
  <h2>My CD Collection</h2>
  <table border="1">
    <tr bgcolor="#9acd32">
      <th>Title</th>
      <th>Artist</th>
    </tr>
    <xsl:for-each select="catalog/cd">
    <tr>
      <td><xsl:value-of select="title_"/></td>
      <td><xsl:value-of select="artist"/></td>
      <td>
          <xsl:variable name="NotStarted" select="preceding-sibling::cd[1]/company" />
          <xsl:choose>
            <xsl:when test="company != '---'">
              <xsl:value-of select="company"/>
            </xsl:when>
            <xsl:otherwise>
              <xsl:copy-of select="$NotStarted" />
            </xsl:otherwise>
          </xsl:choose>
      </td>
    </tr>
    </xsl:for-each>
  </table>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet> 
正如预期的那样,我得到了下一个 html
Title   Artist
Empire Burlesque    Bobby   Columbia
Shirt2  Bobby   Columbia2
Fingers Bobby   Columbia3
Zip1    Bobby   Columbia3
Zip2    Bobby   ---
我如何迭代以获取最后一个有意义的字符串来替换或任何其他方式?谢谢。