Data flow diagram for a comprehensive hotel management system featuring customer authentication, room and service inventory management, booking workflows, and payment processing via VNPAY. The architecture separates concerns across presentation, application, and data layers, with 10 core processes handling user profiles, room/zone catalogs, service offerings, voucher management, reservations, payments, refunds, reviews, and notifications. This multi-tenant design demonstrates best practices for hospitality platforms requiring secure OTP-based authentication, real-time inventory updates, and integrated payment gateways. Fork and customize this diagram on Diagrams.so to adapt the data stores, add additional processes, or integrate alternative payment providers and notification channels.