There are times when the parameter values for the simple requests in a batch
request are the same, for example, ItemType=ASIN. In this case,
instead of using a ReferenceNumber for each simple request, you can substitute
the special value, "Shared,", as shown in the following
example.
ItemLookup.Shared.ItemType=ASIN
The following parameter declarations show the equivalent of the preceding
declaration.
Both forms of the request work but using the special value, Shared, reduces
the amount of typing required. Generally, you only use the Shared value with
required parameters. Optional parameters do not need to be included in the
request and their default values, if any, are assumed and thus shared across the
simple requests in the batch request.