allownegativeassertions- Type: boolean
类型：布尔类型 - Valid on any element that has a
datasourcesattribute. When multiple datasources are used, one may override an assertion from another. This attribute, iftrue, which is the default, allows a datasource to negate an earlier assertion.
适用于任何有datasources属性的元素。当使用多个数据源，一个数据源可以指定覆盖另一个。这个属性，如果为真，这是默认值，允许一个数据源覆盖之前的数据源。