使用xslt-3将元素从xml文件移动到另一个xml元素

Question

给出以下示例xml文件：

<?xml version="1.0"?>
        <catalog>
           <book id="bk101">
              <author>Gambardella, Matthew</author>
              <title>XML Developer's Guide</title>
              <genre>Computer</genre>
              <price>44.95</price>
              <publish_date>2000-10-01</publish_date>
              <description>An in-depth look at creating applications 
              with XML.</description>
           </book>
           <book id="bk102">
              <author>Ralls, Kim</author>
              <title>Midnight Rain</title>
              <genre>Fantasy</genre>
              <price>5.95</price>
              <publish_date>2000-12-16</publish_date>
              <description>A former architect battles corporate zombies, 
              an evil sorceress, and her own childhood to become queen 
              of the world.</description>
           </book>
           <book id="bk103">
              <title>Maeve Ascendant</title>
              <genre>Fantasy</genre>
              <price>5.95</price>
              <publish_date>2000-11-17</publish_date>
              <description>After the collapse of a nanotechnology 
              society in England, the young survivors lay the 
              foundation for a new society.</description>
           </book>
        </catalog>

我需要通过规则将所有title元素合并到author元素中： 如果author元素已经存在，那么title元素的值将被插入到作者记录中，使用分隔符，即|字符。 如果记录中没有author元素，则title元素将成为author元素。 期望的输出：

 <?xml version="1.0"?>
        <catalog>
           <book id="bk101">
              <author>Gambardella, Matthew | XML Developer's Guide</author>
              <genre>Computer</genre>
              <price>44.95</price>
              <publish_date>2000-10-01</publish_date>
              <description>An in-depth look at creating applications 
              with XML.</description>
           </book>
           <book id="bk102">
              <author>Ralls, Kim | Midnight Rain</author>
              <genre>Fantasy</genre>
              <price>5.95</price>
              <publish_date>2000-12-16</publish_date>
              <description>A former architect battles corporate zombies, 
              an evil sorceress, and her own childhood to become queen 
              of the world.</description>
           </book>
           <book id="bk103">
              <author>Maeve Ascendant</author>
              <genre>Fantasy</genre>
              <price>5.95</price>
              <publish_date>2000-11-17</publish_date>
              <description>After the collapse of a nanotechnology 
              society in England, the young survivors lay the 
              foundation for a new society.</description>
           </book>
        </catalog>

如何使用xslt-3实现上述结果？