Parameters that differ between the simple requests in a batch request are identified by a reference number. The following parameter declaration syntax shows where the reference number goes.

OperationName.ReferenceNumber.Parameter=Value

The following request snippet shows an example of a reference number, 1.

ItemLookup.1.ItemId=0976925524

The ReferenceNumber is a positive integer that associates the parameters in the simple request. For example, the following parameters are part of the same simple request because they use the same reference number.

ItemLookup.1.ItemId=0976925524&
ItemLookup.1.ResponseGroup=Images

These parameters might be different from a second simple request, which is part of the same batch request.

ItemLookup.2.ItemId=0485935524&
ItemLookup.2.ResponseGroup=Collections

So, if the previous two request snippets were part of one batch request, the ItemLookup operation would be executed twice, each time with a different ItemId and ResponseGroup.

In one batch request, you can have up to two different reference numbers. For example, the following request snippet exceeds the number of allowed reference numbers in one batch request.

ItemLookup.1.ItemId=0976925524&
ItemLookup.2.ItemId=0485935524&
ItemLookup.3.ItemId=0792335535&