Isn't this where you use the xs:hexBinary constructor?  I have examples in my IBM4690 TLOG ACE schema where I need to check that the content of a hexBinary field is a certain value and it works as desired with IBM DFDL.

  <xs:element dfdl:length="1" dfdl:lengthKind="explicit" fixed="13"
              name="SubStringType" type="type_PS">
        <xs:annotation>
                <xs:appinfo source="http://www.ogf.org/dfdl/">
                        <dfdl:discriminator>{. eq xs:hexBinary('13')}</dfdl:discriminator>
                </xs:appinfo>
        </xs:annotation>
  </xs:element>


  <xs:element dfdl:length="1" dfdl:lengthKind="explicit" fixed="BB"
              name="SubStringType" type="type_PS">
        <xs:annotation>
                <xs:appinfo source="http://www.ogf.org/dfdl/">
                        <dfdl:discriminator>{. eq xs:hexBinary('BB')}</dfdl:discriminator>
                </xs:appinfo>
        </xs:annotation>
  </xs:element>

Then Mike's example would look like:

{ if (xs:hexBinary(../magicNum) eq xs:hexBinary('a1b2c3d4') then 'bigEndian'
  else if (xs:hexBinary(../magicNum) eq xs:hexBinary('d4c3b2a1') then 'littleEndian'
 else error() }

Regards

Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848



From:        Tim Kimber/UK/IBM@IBMGB
To:        dfdl-wg@ogf.org,
Date:        13/06/2013 11:27
Subject:        Re: [DFDL-WG] DFDL Expressions and hex literal constants
Sent by:        dfdl-wg-bounces@ogf.org

---

XPath uses XML schema lexical formats for all simple types. The XML Schema lexical format for an integer does not allow a hexadecimal option.
The standard solution is to create a pair of custom XPath functions that convert between hex and decimal lexical formats. But that's not a viable solution for a DFDL modeller because they cannot define custom XPath functions.

regards,

Tim Kimber, DFDL Team,
Hursley, UK
Internet:  kimbert@uk.ibm.com
Tel. 01962-816742  
Internal tel. 37246742




From:        Steve Hanson/UK/IBM@IBMGB
To:        Mike Beckerle <mbeckerle.dfdl@gmail.com>,
Cc:        dfdl-wg@ogf.org, dfdl-wg-bounces@ogf.org
Date:        13/06/2013 10:39
Subject:        Re: [DFDL-WG] DFDL Expressions and hex literal constants
Sent by:        dfdl-wg-bounces@ogf.org

---

Mike

I think there might be a wider problem in specifying any hex in XPath expressions.  Tim's been looking into this as part of an IBM DFDL defect.

Regards

Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848



From:        Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:        dfdl-wg@ogf.org,
Date:        13/06/2013 00:24
Subject:        [DFDL-WG] DFDL Expressions and hex literal constants
Sent by:        dfdl-wg-bounces@ogf.org

---

I haven't found a way in XPath to specify a hexadecimal integer number.

E.g., I want to write expressions like
{ if (../magicNum eq 0xa1b2c3d4) then 'bigEndian'
else if (.../magicNum eq 0xd4c3b2a1) then 'littleEndian'
  else error()
}

But it rejects the 0x notation. Do I really have to write decimal everywhere? When dealing with binary data this is a bit of a nightmare.

I think the above code is clear to anyone, but if I convert those numbers to decimal it becomes completely obscure.

...mike

--
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com
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Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU--
 dfdl-wg mailing list
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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