1. once an element is matched by one template, then all its descent elements would not be applied with templates

2. scan xml source elements according to the order in the document text

scan order peudo-code

 

  function doElement(xmlElement) {
     //try if we have a template that can apply this element
     templeate1=all the best matched template from all templates;
     if (template1 is not null) {
        apply template1 to xmlElement;
        return;
     }

     //go deeper to the child elements
     children=get all children of xmlement;
     for each element1 of children {
        doElement(element1)
     }   

  }

xml

<?xml version="1.0" encoding="UTF-8"?>
<root>

  <AA id="aa1"> AA1 </AA>
  <AA id="aa2"> Have BB 
     <BB id="aa2bb1"> AA2BB1 </BB>
  </AA>
  <CC id="cc1">  
     <BB id="cc1bb2"></BB>
  </CC>

  <BB id="bb1"> BB1 </BB>
  <BB id="bb2"> BB2 </BB>
  <BB id="bb3"> BB3 </BB>

  <AA id="aa4"> AA4 </AA>
  <AA id="aa5"> AA5 </AA>

</root>

stylesheet

<?xml version="1.0" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:template match="BB">
    <b>
      name=<xsl:value-of select="name()"/>
      id=<xsl:value-of select="@id"/>
    </b>
	</xsl:template>

  <xsl:template match="AA">
    <a>
      <xsl:value-of select="name()"/>
      <xsl:value-of select="@id"/>
    </a>
	</xsl:template>
	

</xsl:stylesheet>

output

<?xml version="1.0" encoding="UTF-8"?>

  <a>AAaa1</a>
  <a>AAaa2</a>
    
     <b>
      name=BB
      id=cc1bb2</b>
  

  <b>
      name=BB
      id=bb1</b>
  <b>
      name=BB
      id=bb2</b>
  <b>
      name=BB
      id=bb3</b>

  <a>AAaa4</a>
  <a>AAaa5</a>