The value of a check box or radio button is encoded only if the form element is checked.
只有当对应的表单元素被选中时，复选框和单选按钮的值才会被编码。
2
If the element's type is checkbox or radio, the value is added only if the HTML element is checked.
如果元素的类型为复选框或单选框，只有选中HTML元素时，才会添加值。
3
An XForms implementation has to respond to user-directed events relating to an XML document (for example, the element that might be selected when a user chooses from radio buttons).
X Forms实现需要响应与XML文档有关的用户指定的事件(例如，用户通过选择单选按钮时选择的事件)。