In XSLT 2.0, when your context node is the parent of the nodes you have shown, <xsl:value-of select="*"/> does exactly what you want.
In 1.0, use
<out>
<xsl:for-each select="*">
<xsl:value-of select="."/>
<xsl:if test="position() != last()">
<xsl:text> </xsl:text>
</xsl:if>
</xsl:for-each>
</out>
Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference