Currently we are reading user data from database for our section access table.
As an alternative we are looking to read the same from a web service.
Please advise the steps to implement the same
As long as you can load the data from your web service in your load script then yes.
The details of how to do this will depend on the details of your web service.
...and "as long as the web service provides NTNAME-compatible values as part of the user details" would also be a nice requirement I think
Retrieving data ...