The first form is looking at the physical data and seeing if its length is 0 bytes. It can be used for any simple type.

The second form is looking at the logical value of the data and seeing it has the value empty string. It can be used only is type is xs:string or xs:hexBinary.

Only if the type of Empty is xs:string or xs:hexBinary are these functionally equal.

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:        "Garriss Jr., James P." <jgarriss@mitre.org>
To:        "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>,
Date:        03/06/2013 13:40
Subject:        [DFDL-WG] 0 equals ""?
Sent by:        dfdl-wg-bounces@ogf.org

---

When are these not functionally equal?
 
                        <dfdl:discriminator>{ dfdl:valueLength(../Empty, "bytes") eq 0 }</dfdl:discriminator>
                       <dfdl:discriminator>{ ../Empty eq "" }</dfdl:discriminator>
 
TIA--
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