how do i set the condition if the child has empty string:

<parent>
  <ch1>
    <data>data1</data>
    <data></data>
    <data>data3</data>
  </ch1>
  <ch1>
    <data>data4</data>
    <data></data>
    <data>data6</data>
  </ch1>
</parent>


 <xsl:for-each select="ch1">
  <xsl:if test="data= '' ">
   <xsl:apply-templates select="data"/>
  </xsl:if>
 </xsl:for-each>

i just want to print <data> tag that has text, if it doesn't contain any, don't print it

how to write the if condition?

Your code is saying "if any of the data elements is equal to "" then apply-templates to all the data elements".

Just replace

 <xsl:for-each select="ch1">
  <xsl:if test="data= '' ">
   <xsl:apply-templates select="data"/>
  </xsl:if>
 </xsl:for-each>

with

<xsl:apply-templates select="ch1/data[string(.)]"/>

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

sorry my bad,
<xsl:if test="data= '' ">
that line should be
<xsl:if test="data != '' ">
not equal to

i want to rid off the empty contain