[DFDL-WG] still no need for fn:error - re-assess

Tue Jul 5 14:07:59 EDT 2016

So the fn:error() XPath function takes a problematic argument.

All the arguments are optional, so fn:error() is legal.

The first argument is of type xs:qQName, and we don't have that type in
DFDL. So the best we could do is to accept a string that is in the "form"
of a QName, e.g.,
"foo:bar".

The second argument is a description string, third and subsequent args are
objects. The manner by which this string and objects are provided to the
execution environment is implementation dependent according to the XQuery
and XPath spec, and this is fine for DFDL implementations also.

The lack of the QName type for the first argument suggests we're going to
need to create dfdl:error(string, string, item()*), where the first
argument is a string in the form of a QName, and the other arguments are as
per fn:error.

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>

On Tue, Jul 5, 2016 at 11:49 AM, Steve Hanson <smh at uk.ibm.com> wrote:

> WG agreed that an error function is needed, action 288 raised.
>
> *No*
> *Action *
>
> *288*
> *Decide on error function specification (Mike)*
> 5/7: An error function is useful for expressions when unparsing. Mike to
> evaluate XPath fn:error().
>
>
> Regards
>
> Steve Hanson
> *IBM Integration Bus*
> <http://www-03.ibm.com/software/products/en/ibm-integration-bus>,
> Hursley, UK
> Architect, *IBM DFDL*
> <http://www.ibm.com/developerworks/library/se-dfdl/index.html>
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> *smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
> mob:+44-7717-378890
>
>
>
> From:        Mike Beckerle <mbeckerle.dfdl at gmail.com>
> To:        "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>
> Date:        14/06/2016 17:10
> Subject:        Re: [DFDL-WG] still no need for fn:error
> Sent by:        "dfdl-wg" <dfdl-wg-bounces at ogf.org>
> ------------------------------
>
>
>
> I want to re-open the discussion of fn:error.
>
> Previously we said it was not needed because an assert could be used.
>
> However, we've now run into where we want to cause an error, during
> unparsing, during outputValueCalc.
>
>  <xs:element name="Protocol" type="pcap:bit" dfdl:length="8"
>            dfdl:outputValueCalc="{
>            if (fn:exists(../../pcap:ICMPv4)) then 1
>            else if (fn:exists(../../pcap:TransportLayer/pcap:TCP )) then 6
>            else if (fn:exists(../../pcap:TransportLayer/pcap:UDP )) then 17
>            else -1 }"/>
>
> That -1 at the end. That's an error case. We really want
> fn:error("Unrecognized protocol.")
>
> We can't change to a dfdl:assert, because assertions aren't evaluated when
> unparsing.
>
> Comments?
>
> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
> *www.tresys.com* <http://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>
>
>
> On Thu, Jul 25, 2013 at 9:16 AM, Mike Beckerle <*mbeckerle.dfdl at gmail.com*
> <mbeckerle.dfdl at gmail.com>> wrote:
> Respin of this example:
>
> Here's the example as suggested by Jonathan of how to issue an error that
> I previously was suggesting needed fn:error. I'm convinced this is
> sufficient and we can avoid the need for fn:error now.
>
> <xs:element name="magic_number" type="ex:uint32"
> dfdl:byteOrder="bigEndian">
>  <xs:annotation>
>    <xs:appinfo source="*http://www.ogf.org/dfdl/*
> <http://www.ogf.org/dfdl/dfdl-1.0/>">
>      <dfdl:assert
>        test="{ (xs:unsignedInt(.) eq *dfdl:unsignedInt('xa1b2c3d4')*) |
>                (xs:unsignedInt(.) eq *dfdl:unsignedInt('xd4c3b2a1')*) }"
>        message="{ fn:concat(
>                      'Magic number ',
>                      dfdl:hexBinary(dfdl:unsignedInt(.)),
>                      ' was not 0xA1B2C3D4 (for bigEndian) or 0xD4C3B2A1
> (for littleEndian).' }" />
>    <dfdl:setVariable ref="ex:bOrd">{ xs:unsignedInt(.) }<dfdl:setVariable>
>    </xs:appinfo>
>  </xs:annotation>
> </xs:element>
>
>
> On Wed, Jul 24, 2013 at 11:58 AM, Steve Hanson <*smh at uk.ibm.com*
> <smh at uk.ibm.com>> wrote:
> Mike,  I think you meant:
>
>        test="{ (xs:unsignedInt(.) eq *dfdl:unsignedInt('xa1b2c3d4')*) |
>                (xs:unsignedInt(.) eq *dfdl:unsignedInt('xd4c3b2a1')*) }"
>
>
> Regards
>
> Steve Hanson
> Architect, IBM Data Format Description Language (DFDL)
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK
> *smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:*+44-1962-815848* <%2B44-1962-815848>
>
>
>
> From:        Mike Beckerle <*mbeckerle.dfdl at gmail.com*
> <mbeckerle.dfdl at gmail.com>>
> To:        *dfdl-wg at ogf.org* <dfdl-wg at ogf.org>,
> Date:        24/07/2013 16:46
> Subject:        [DFDL-WG] still no need for fn:error
> Sent by:        *dfdl-wg-bounces at ogf.org* <dfdl-wg-bounces at ogf.org>
> ------------------------------
>
>
>
> Here's the example as suggested by Jonathan of how to issue an error that
> I previously was suggesting needed fn:error. I'm convinced this is
> sufficient and we can avoid the need for fn:error now.
>
> <xs:element name="magic_number" type="ex:uint32"
> dfdl:byteOrder="bigEndian">
>  <xs:annotation>
>    <xs:appinfo source="*http://www.ogf.org/dfdl/*
> <http://www.ogf.org/dfdl/dfdl-1.0/>">
>      <dfdl:assert
>        test="{ (xs:unsignedInt(.) eq *dfdl:unsignedInt('xa1b2c3d4')*) |
>                (xs:unsignedInt(.) eq *dfdl:unsignedInt('xd4c3b2a1')*) }"
>        message="{ fn:concat(
>                      'Magic number ',
>                      dfdl:hexBinary(dfdl:unsignedInt(.)),
>                      ' was not 0xA1B2C3D4 (for bigEndian) or 0xD4C3B2A1
> (for littleEndian).' }" />
>    <dfdl:setVariable ref="ex:bOrd">{ xs:unsignedInt(.) }<dfdl:setVariable>
>    </xs:appinfo>
>  </xs:annotation>
> </xs:element>
>
>
> --
> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
> *www.tresys.com* <http://www.tresys.com/>
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>
>
>
> --
> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
> *www.tresys.com* <http://www.tresys.com/>
>
> --
>  dfdl-wg mailing list
>  dfdl-wg at 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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