A public interface that is deemed obsolete will:
1. Have its references in the code refactored to use other interfaces.
2. Generate warnings when used. When possible, the warning will include information about what should be done to avoid using this interface. (Alternative interface, etc)
3. All public interfaces will be preserved for at least one full release after they have been deprecated. Often they will be preserved for much longer.
4. Disk formats will be supported for at least 6 months after they have been deprecated.
This time period is known as the "deprecation phase" for that interface, after which its implementation will be removed from the code.