How do you treat business starting / preliminary expenses in accounting?

Preliminary expenses, which incurred for before commencement of business. For setting up of any undertaking or business (Preparation of feasibility report, project report or for conducting market survey or any other survey or engineering services relating to the business and Legal charges for drafting any agreement for setting up or for conduct of any business). 

It has a special nature of an asset in financial statements and as per prudent accounting principal should be write off in P&L A/c in a defferd way over the years. 

I understand that these are depreciatble assets during a specific period determined by local laws.