DFDL is pretty limited when it comes to ignoring things in the infoset. I can't
think of a good way to do what you're suggesting.
I think generally the recommended approach for something like this is to filter
the infoset prior to unparsing. For example, an XSLT could do what you want in
one line (with the rest being standard XSLT boilerplate):
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<!-- standard identity transform: copy everything -->
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
<!-- override to not copy "person" elements where rsvp is not "Yes" -->
<xsl:template match="person[not(rsvp='Yes')]" />
</xsl:stylesheet>
There's a lot of things to dislike about XSLT, but is pretty powerful when it
comes to filtering XML, so generally makes it a better tool for that kindof
thing than DFDL.
You aren't limited to XSLT though--languages like Python/Javascript/Scala have
good XML support for finding and removing elements, so that is also an option.
Though they usually require a few more lines of code than XSLT and aren't
declarative like XSLT and DFDL, which has advantages.
On 2025-10-02 09:01 AM, Mark Kozak wrote:
Hello community,
I have a situation where I would like to discard parts of a parsed data file if
that part is invalid. After trying several approaches using hidden groups and
output value calculations, I am starting to think it just can’t be done. But I
wanted to check with the community before I hang up the effort.
Below is a simplified example of a schema that will illustrate the use case.
Suppose we have a file of names and want to unparse only the elements where RSVP
is equal to ‘Yes’. Not being able to use dfdl:inputValueCalc on a complex type
appears to be a limiting factor here. In the real world the complex types are
quite complex so copying each simple element in the array one by one is untenable.
Any shared thoughts will be very much appreciated.
Thanks,
Mark
Mark Kozak
Director of Engineering
Adeptus Cyber Solutions
Adeptus-CS.com
