Permissions to schema

Hi,

 

I have the structure on Postgre:

 

database:  dbGlobal

 

schema1:         sch_sist1     owner sch_sist1:  john

 

schema2          sch_sist2     owner sch_sist2:  mary

 

 

I' m using pgAdmin III.

 

Is there a way to avoid the mary to access the schema sch_sist1 ?

 

I don't want that mary see/access the schema of john and I don't want that john see/access the schema of mary.

 

Anybody has a solution.

 

Thanks a lot.

 

Eduardo