SQUID is a P2P system for integrating and querying data sources distributed over a network (Internet, Intranet). It presents itself as a layer capable of interfacing with pre-existing systems and making them interact in an absolutely transparent way for the user. The system allows each node in the network to import data from the other nodes, remodeling the structure.
Typically this data is managed by a DBMS (ORACLE, MySQL, SQL Server, etc.) or resides on other sources (text files, XLS files, XML files, etc.).