unparsing with dfdl:setVariable referring to dfdl:outputValueCalc element
I somehow think we already discussed this, but am unable to find the thread. Suppose: <xs:element name="len" type="xs:int" dfdl:outputValueCalc="{ dfdl:valueLength(../data) + 10 }"/> <xs:sequence><xs:annotation><xs:appinfo ...> <dfdl:setVariable name="var">{ ../len }" /> </xs:appinfo></xs:annotation></xs:setVariable> <xs:element name="data" dfdl:length="{ $var }"> .... </xs:element> In the above, when unparsing, the output value calc for len can be evaluated, but we must delay its evaluation and unparsing until the subsequent data element is available. The next thing the unparse has to do, after delaying the unparsing of 'len' is set the var variable. This requires the value of len, which has been deferred. We have real schemas (e.g., even PCAP) where this occurs. This breaks the rule that when variables are evaluated, things they reference must have already been evaluated. Basically, when we delay evaluating the OVC for len we are suspending anything that depends on len having a value as well. Did we discuss and/or agree on this behavior? I don't have any work around for this. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy <http://www.ogf.org/About/abt_policies.php>
New action 289 raised to clarify the behaviour when element A has an expression that refers back to an element B with OVC which refers ahead of A. Regards Steve Hanson IBM Integration Bus, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org> Date: 25/07/2016 20:59 Subject: [DFDL-WG] unparsing with dfdl:setVariable referring to dfdl:outputValueCalc element Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org> I somehow think we already discussed this, but am unable to find the thread. Suppose: <xs:element name="len" type="xs:int" dfdl:outputValueCalc="{ dfdl:valueLength(../data) + 10 }"/> <xs:sequence><xs:annotation><xs:appinfo ...> <dfdl:setVariable name="var">{ ../len }" /> </xs:appinfo></xs:annotation></xs:setVariable> <xs:element name="data" dfdl:length="{ $var }"> .... </xs:element> In the above, when unparsing, the output value calc for len can be evaluated, but we must delay its evaluation and unparsing until the subsequent data element is available. The next thing the unparse has to do, after delaying the unparsing of 'len' is set the var variable. This requires the value of len, which has been deferred. We have real schemas (e.g., even PCAP) where this occurs. This breaks the rule that when variables are evaluated, things they reference must have already been evaluated. Basically, when we delay evaluating the OVC for len we are suspending anything that depends on len having a value as well. Did we discuss and/or agree on this behavior? I don't have any work around for this. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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Mike Beckerle -
Steve Hanson