xml tag checking using call transformation in ABAP (t-code: XSLT_TOOL)

Transforming data from xml tag to internal table with checking (whether the tag exits or not)

<tt:cond s-check="not-initial(ref('QUANTITY'))">
<Quantity tt:value-ref="QUANTITY"/>
</tt:cond>

<tt:cond s-check="initial(ref('QUANTITY'))">
<Quantity tt:value-ref="QUANTITY"/>
</tt:cond>


Transforming data from xml tag to internal table without checking-

 <Quantity tt:value-ref="QUANTITY"/>


Quantity  = xml tag
QUANTITY = internal table field