Requirements for a View Link
A view link must comply with the following requirements:
An aggregate category link can include multiple aggregate view, detail category, and detail view links.
A detail category link can only include detail links.
You can define an aggregate view link in the following ways:
Without a parent category
With an aggregate category as the parent category
You cannot define a detail category as the parent category of an aggregate view link.
You must define an aggregate category or detail category as the parent category of a detail view link.
You cannot use a detail category as the parent category of an aggregate view.
An aggregate category cannot define a parent category.