Layout Hierarchy for iViews and Web Applications 
Depending on the container elements used, different application types can have different layout hierarchies. In the case of the portal environment, there are Web applications and iViews. Both application types use different containers, serve different purposes, and therefore differ in complexity with respect to the layout.
iView
Tray = iView container
Tabstrip - may contain:
Group (if it is not the only element)
Subgroup
Table View (if it is not the only element)
Simple Elements
Separators
Group - may contain:
Group (if it is not the only element, different group types only)
Subgroup
Table View (if it is not the only element)
Simple Elements
Separators
Subgroup - may contain:
Simple Elements
Separators
Table View
Simple Elements
Separators
Generally, there should not be more than one level of nesting within trays/iViews. Also note that tabstrips may not be nested.
Simple elements are: input fields, selection elements, text, buttons, ...
Note
A similar tree can be created for real iViews based on the elements used.
Web Application
Application Background = Window/frame background = application container
Area - may contain:
Tabstrip - may contain:
Group (if it is not the only element)
Subgroup
Table View (if it is not the only element)
Simple Elements
Separators
Group - may contain:
Tabstrip (if it is not the only element)
Group (if it is not the only element, different group types only)
Subgroup
Table View (if it is not the only element)
Simple Elements
Separators
Subgroup - may contain:
Simple Elements
Separators
Table View
Simple Elements
Separators
Single elements
Generally, there should not be more than one level of nesting within Web applications. Also note that tabstrips may not be nested.
Simple elements are: input fields, selection elements, text, buttons, ...
Note
A similar tree can be created for real Web applications, based on the elements used.
The critical question for Web applications is, whether single elements and containers other than areas can be placed on the application background. Currently, the application background may not be used for non-container elements (see the IAC Guidelines in the SAP Design Guild). In SAP applications, header data may be placed on the application background; there is no such a container concept in SAP applications as areas.