- From: Robie, Jonathan <jonathan.robie@emc.com>
- Date: Tue, 29 Sep 2015 12:51:50 +0000
- To: Abel Braaksma <abel.braaksma@xs4all.nl>, "'Public Joint XSLT XQuery XPath'" <public-xsl-query@w3.org>
Mike Kay wrote: >> In the query of XPath / XQuery per se, is there ever a need to allow xs:error >> as a sequence type? > > We don’t allow it because there is a use case, we allow it because there is no reason not to. > We don’t disallow multiplication by zero just because we can’t see why anyone would want > to do it. I think there are some important differences between xs:error and 0. 0 is a value. It can be assigned to variables and used in expressions. If xs:error is the result of any operation, it is an error, not a value that can be used in expressions. And if I take your analogy seriously, we should allow division by xs:error. I don't think you are suggesting that. We allow division by zero because we allow division by a numeric value, and don't want to create lots of special cases. But xs:error is not a value that can occur. The simplest fix really might be to say that xs:error, used as a SequenceType, is always a type error. That significantly simplifies specification, test cases, and implementation. Jonathan
Received on Tuesday, 29 September 2015 12:52:35 UTC