Difference between Migration and Upgrade

[sri.accord]

Hello Friends , Could you please share your views on upgrade and migration.what is the difference between them?Please  share your knowledge.I have an interview tomorrow and if any one has migration documnets , please send to sri.accord@gmail.com.
Thank you,
Sri.

[MFGF]

In a nutshell, migration is the process of moving from one architecture to another, for example migrating a Business Objects Universe and Reports into the Cognos 8 environment.  Upgrading is the process of moving to a newer release of the same architecture, for example, upgrading a Cognos 8.3 environment to the 8.4 release of Cognos 8.

I also like to use an analogy to help non-technical users to understand the difference.  I compare migration to the process of moving house.  The fittings and furniture in your current house are moved and placed into the new house, but some of them may not fit properly or be redundant in the new house, depending on its layout and standard fittings.  I describe upgrading as the process of redecorating your existing house.  If the furniture and fittings are removed for this process, you should be able to guarantee that they all fit nicely back into their original places once the redecoration is complete.

Regards,

MF.