BI-IP Characteristic

Hi

I want to add characteristic relationship to a BI-IP model. The help docs stats:

'We recommend that you derive your own class from the example class 'CL_RSPLS_CR_EXIT_BASE'. You then only have to implement the methods ‘CHECK’, ‘DERIVE’ and ‘CREATE’. The class 'CL_RSPLS_CR_EXIT_BASE' itself can be used directly, but it does not execute an action.'

How do you derive a class from the sample class and how would you implement the methods as stated above. I have done this in BPS but not yet in IP. Please help...

L.