BC data source and functional module

Hi Gurus

I know that we can extract data via functional module in case of generic extractor but when we use business content data source ( for ex.0MAT_PLANT_ATTR) is it possible to use functional module to extract the data?

How can we find the functional module? my requirement is I need to enhance this data source with few more attributes.

Pl help. also advise where I need to write the code?