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Re: [xml-dev] XML Schema complex type restriction

On 29 September 2017 at 14:09, Michael Kay <mike@saxonica.com> wrote:
More realistically, imagine you have a complex type whose content model is <element name="para" minOccurs="0" maxOccurs="unbounded"/>, and the assertion says test="exists(para)", then the assertion on its own would allow


which the complex type's grammar does not allow.

Requiring the assertion to be true ONLY for content that satisfies the grammar would be a ridiculous burden on schema authors.
Thanks for sharing this example. In this, the assertion has violated the constraint defined by the grammar. I think, this is an anti-pattern for using an assertion.

Please consider the following example:

XML instance

<?xml version="1.0"?>

The corresponding XSD 1.1 schema

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
   <xs:element name="speed">
           <xs:element name="from" type="xs:positiveInteger"/>
           <xs:element name="to" type="xs:positiveInteger"/>
        <xs:assert test="from lt to"/>

IMHO, these are the sort of use cases, where assertions are quite useful.

Mukul Gandhi

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