Input:

<?xml version="1.0" encoding="UTF-8"?>
<article>
	<meta productid="CIJB" volumenum="22">
		<journalcode>CIJB</journalcode>
		<issn type="print">0269-2171</issn>
		<issn type="electronic">1465-3486</issn>
	</meta>
</article>

Desired Output:

<?xml version="1.0" encoding="UTF-8"?>
<article>
	<meta productid="CIJB" volumenum="22">
		<journalcode dummy="CIJB"/>
		<issn type="print" dummy="0269-2171"/>
		<issn type="electronic" dummy="1465-3486"/>
	</meta>
</article>

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

  <xsl:template match="journalcode | issn"><!-- for these two -->
    <xsl:copy><!-- copy element -->
      <xsl:copy-of select="@*"/><!-- copy attributes -->
      <xsl:attribute name="dummy"><!-- put string value into @dummy -->
        <xsl:value-of select="."/>
      </xsl:attribute>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="@*|node()"><!-- leave rest unchanged -->
    <xsl:copy>
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>