Id-a unique identifier for the constraint.

id -约束的惟一标识符。

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If the constraint has a message associated with it (through the message Id), the {0} variable in the message is substituted by the context element — unless it is between single quotes.

如果约束使用了一个消息关联(通过消息id)，消息中的{0}变量就被上下文的元素所取代——处非它使用单引号括住。

youdao

Now you set the store ID and supplier ID fields so that they do not accept an empty value. Of course, you can add a schema constraint into the XForms model to achieve this.

现在，设置store ID和supplier ID字段以使这两个字段不接受空值。

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