DZone

Enterprise data structures are not usually flat. More often they are hierarchical, nesting one or more levels deep. For example, an account object might contain a customer object, which might contain an address object, and so on.

Such data structures are often returned by web services. A single call to the server requires less code and incurs less network overhead than multiple calls to retrieve the same information. Often, these data structures are returned as JSON and mapped to strongly typed equivalents such as Java beans on the client side. This works well when modeling the complete server response; however, it can be overkill when only a small subset of the returned data is required.

Source: DZone