WDK中关键词"notdefined"的含义
关键词“notdefined”用来确定当前的action或component在当前的scope（即r_object_type）中是否有效，为true则无效。用来屏蔽action或component从父类型向当前子类型的应用。开发指导文档中有如下一段话：
1.About Component:
notdefined: Configurations can hide elements that are defined in the parent scope by using the
notdefined attribute. Refer to Hiding a component for specific contexts, page 252 for more information.
In the following example, the checkout component is not available for folders:
<scope type='dm_folder'>
<component id="checkout" notdefined="true"></component>
</scope>
2.About Action
If an action definition is scoped to a specific object type, the definition applies to subtypes of the type.
To turn off the action for certain subtypes, create a scoped definition for the subtype and use the
notdefined attribute. In the following example, the checkout action does not apply to folders:
<scope type='dm_folder'>
<action id="checkout" notdefined="true"></action>
</scope>
