Question on Header-Detail programming.

[Boaz Bezborodko]

I've programmed a few Header-Detail applications where I used a set of 
line-numbers for the detail, but each set of line-numbers starts with 
1.  The uniqueness of each detail is based on the combination of the 
header number (say invoice number or order number) and the line number.  
I was watching John's Survivor Series where he says to use a unique 
number for each detail record. 


What is the advantages/disadvantages of using his method versus the way 
I've used them in the past?