hi all,
Basically the shortcut or smart join are special type of 
join by which we can reduce the complexcity of report and 
avoid loop like 

            T1 key1

                             T2 key2
            T3 key3
       then in universe there t2 is fac table and t1 an t2 
are lookup table then if we want some data frm t3 table by 
the foraigan key T1 to T3 then if we creat a simply join 
then that is make a loop and aslo that join search the huge 
fac table aslo so there is new smart or shortcut join by 
which we can join t1 to t3 its show in dotted line in 
univeres designer and does not create and loop

To make it simple short cut joins are used to reduce the 
joins in the Query which will increase the performance of 
the query