[DFDL-WG] clarification: fn:exactly-one function
Andrew Edwards
andy.edwards at uk.ibm.com
Mon Nov 3 09:11:45 EST 2014
HI Mike(et al)
I would suggest that we already have a function that can return true when
the count is 1 and false in all other cases: (fn:count($arg) == 1)
would achieve the same.
It sounds like fn:exactly-one is design to act like an assertion in XPath.
I'm more concerned that XPath returns $arg on success, and we return
"true".
Andy
Andy Edwards - IBM Integration Bus - DFDL
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From: Mike Beckerle <mbeckerle.dfdl at gmail.com>
To: "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>
Date: 30/10/2014 10:00
Subject: [DFDL-WG] clarification: fn:exactly-one function
Sent by: dfdl-wg-bounces at ogf.org
According to the DFDL spec, fn:exactly-one returns "True if the provided
sequence contains exactly one node/value," which suggests that the
function would return false if the sequence contains > or < 1 node/value.
The XPath description states that fn:exactly-one "returns $arg if it
contains exactly one item. Otherwise, raises an error."
It seems of value to have a true/false result, because something that
raises an error like this can only be used as an assertion effectively. On
the other hand, that's not what XPath does.
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
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