Hi, I'm making a hotel reservation website for my course and one of the requirements reads as follows:- I'm not asking for code, just wondering what you think this means. Booking completion rules I'm thinking: Filter form input Make sure the database has all required attributes filled. Web Service for final step Not to sure, like PayPal's payment processing (API?), I have a link directory, but that sorts paypal out for me, I'm unsure what a Web Service is. EDIT - Oh, I should mention I'll be using a Linux host, PHP, MySQL and also using AJAX should that make the difference Thanks!