If you are asking about compress OR, I cannot tell right 
now. But by using descriptive Programming, we can reduce 
the size.
Come to second:
Even though we can write user defined Synchroniz functin 
for web application, it may fail many times. 

P.
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Using Descriptive Programming we can reduce the size of 
Object Repository. No need to Maintain object Reposity if u 
use descriptive Programming Concepts. QTP recognize each 
object with some unique Property values. So you no need to 
add object to object repository if you use descriptive 
programming. Descriptive programming reduces the time of 
QTP to recognize the object uniquely. If you use Object 
Ropository, first QTP retrieves all objects from it and 
verify each property values of the object and it is time 
taken process. If the number of objects in Object 
Repository are huge, QTP takes so much time to recognize 
the object you specified in the Script.

The following Properties can be used to recognize the 
objects uniquely by QTP.
Object Name         Properties to recognize the object
Browser             Name
Page                Title
WebEdit             Name
WebEelemt           InnerText/Html id
WebList             Name
WebButton           Name
Link                Name
WebTable            Html id/Name