When using a federated search tool such as EBSCOhost Integrated Search, most database providers allow the federated search tool to connect to and search their subscription databases.
However, the database providers limit the amount of data that can be searched and how it can be searched. These database providers determine which Limiters, Expanders, Boolean Operators, etc. they allow federated search tools to search. For example, while some database providers allow Author and Title searches, others may only allow Full text, Peer Reviewed and Date to be searched.
Database providers decide how much data they want to provide to federated search providers. The objective of a database provider (external resource) who is working with federated search products is to provide the users with results via the federated search tool but, ultimately, get you to their webpage to perform a detailed search.
For example, if you search for AU Smith, connectors that do not support Author searching may return results with the word Smith in the title or abstract fields or whichever fields they allow.