Migrate Bex to BO 4.0

Hi All,

Can anyone throw flashlight on the following

1) How to migrate SAP Bex to BO in SAP BO4.0

2) How the variables and filters are converted from Bex to WEBI in WEBI reports

3) How to migrate SAP Bex to BO in SAP BOXI 3.1

Please share how to guide links /documents for same

Thanks

Basko