The general solution in DFDL is to use the combination of an optional
repeating element inside a hidden group.
You need to be careful that this optional hidden element does not consume
the next piece of wanted data by mistake. If all the unwanted elements
have known initiators then you are ok. If you don't know the initiators,
but know what is coming next, then one approach is as follows:
xs:complexType
xs:sequence
xs:sequence
xs:complexType
xs:sequence
xsd:annotationhttp://www.ogf.org/dfdl/">
The hidden loop should consume all header lines that do not start with
"Subject:" and stop when it reaches one that does.
I've used a terminator for the header lines, you may have used a separator
with separatorPolicy 'suppressed'. Either should work, but the terminator
gives you the opportunity to handle data where the final CRLF is missing
(via property dfdl:documentFinalTerminatorCanBeMissing).
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
From: "Garriss Jr., James P."
To: "dfdl-wg@ogf.org" ,
Date: 01/03/2013 13:15
Subject: [DFDL-WG] Can I ignore data I don't want in DFDL?
Sent by: dfdl-wg-bounces@ogf.org
Suppose I am using DFDL to parse email headers. Suppose the RFC only
allows 3 headers: To, From, Subject. DFDL can handle this, no problem.
But suppose I get an email that includes a 4th header, one I have not
planned for (i.e., have not included in the DFDL schema), don’t care
about, and don’t want in the infoset. Like so:
From:
To:
Keywords: sales <-- this line should be ignored!
Subject: Latest sales figures
Can DFDL handle this? Does it have a mechanism for allowing me to ignore
(and thus drop) data I haven’t planned for and don’t care about?--
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