At 9:10 AM
Feed entries are
a
b
c
X
Y

newly added entries are a,b,c

i read the feed at 9:00am and noted down the entries X,Y
after 10 minutes again i read the feed
using Etag (or) id method i detected that the feed has changed....................

now how to retrieve ( in php/java) those newly added entries of a feed at 9:10 Am?
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i thought of following the below approach

at 9:00 Am notedown the id of latest entry...............................

at 9:10 Am (it is modified) read the feed entries until you get the entry who id is equal to the entry which we stored at 9:00Am. These entries which we read here are newly added ones...............

is this the right approach to get the newly added entries of a feed?
(or) is there any efficient approach ?

--rama