Also, we're trying to reserve expressions that have multiple-returns (aka sequences of more than one value) for potential future use. E.g., should we ever want to add array-valued expressions in the future - a not unlikely extension. So we definitely don't want them "sliding into" use inadvertently. ...mikeb On Tue, Jan 24, 2012 at 4:25 AM, Steve Hanson wrote:

Tim and I have discussed this and we are ok with making these situations schema definition errors rather than processing errors. We've not been able to find a realistic use case where an expression failing in this manner could legitimately be interpreted as failing to discriminate a point of uncertainty. It almost certainly indicates a problem withe the expression or an ambiguity with the model. For example, in the sequence case, the modeler can always return a single element by using a predicate in the expression (eg {../count[1]} )

Regards

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

From: Mike Beckerle To: dfdl-wg@ogf.org Date: 19/01/2012 01:33 Subject: [DFDL-WG] Issue 163: Expressions returning ES - type of error when expression returns wrong type. Sent by: dfdl-wg-bounces@ogf.org ------------------------------

I reviewed section 23. The last paragraph of 23.3 is inconsistent with the rest of the section.

Suggested revised wording:

The result of evaluating the expression must be a single atomic value of the type expected by the context, and it is a schema definition error otherwise. Some XPath expressions naturally return a sequence of values, and in this case it is also schema definition error if an expression returns a sequence containing more than one item. If the expression returns an empty sequence it will be treated as returning *nil*.

-- Mike Beckerle | OGF DFDL WG Co-Chair Tel: *781-330-0412* <781-330-0412> -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg

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-- Mike Beckerle | OGF DFDL WG Co-Chair Tel: 781-330-0412