Consider a global schema defined by the following relations: emp(E): E is an employee phone(E,P): E has P as phone number office(E,O): E has O as...

Now Source1 disappears (becomes unavailable) and a new source comes in, that provides thephone number of their manager for some employees. Do the updates in the GAV and LAVmappings that are required to take into account these changes. What is the approach (GAV orLAV) for which updating the mappings between the global and local relations is easier?