There are two ways to combine the results of two or more component mashable information sources or mashups. Joins work much like database joins. The results of the services may be very different but they have repetitive 'items' and key nodes within those items define how the items are related. See <join> for instructions.

Merges, on the other hand, merge mashable or mashup results that have homogenous, document-type structures just as a database union operation does. See <merge> for instructions.