Any way to create view-entities joining entities from different datasources?

[Christian Carlow]

I assume that for entities of different datasources to be related then 
each of the records from both datasources would have to be looped and 
compared.  I was just wondering if there was some tool out there that 
might leverage having to manually write code to compare the data.  Maybe 
some sort of heterogeneous database query tool?  Such a tool could help 
during migration to OFBiz.