Context level diagram of inventory management system

There are three main external entities in this system:
- Customer
- Supplier
- Admin
Level 1 DFD of inventory management system
Supplier detail: As the name suggests supplier detail sub process record and process all supplier related records. This process send supplier list to the admin. It also send supplier detail to the purchase order sub process.
Sales order: Sales order record and manage all sales to the customers. After each sale stock decreases. This information is passed to the inventory management sub process for maintaining inventory levels.
Purchase order: Purchase order sub process records and manage all the purchase order given to the supplier. Whenever a product purchase happens, the stock of that product increases. This increase in stock in passed to the inventory management sub process.
Inventory management: As the name suggests inventory management sub process maintain sufficient amount of inventory. Whenever a product is sold, the product stock decreases. If the product stock goes below the predefined minimum stock level, it informs purchase process to place purchase order to the supplier to maintain sufficient stock.
Transaction & payment: This process tracks all the sale & purchase transaction and financial transactions.

Level 2 DFD of inventory management system
Level 2 DFD of inventory management system clarify it’s level 1 DFD much deeper. This level explain the working of each sub process and database.
Low level functionality of inventory management system
- Admin can view entire customer list
- Admin can add new product & stock
- Admin can get inventory status
- Admin can view entire supplier list
- Customer can give their details
- Customer can place order
- Customer can receive payment receipt
- Supplier can give their details
- Supplier can receive purchase order
- Supplier can get paid for their order
The database of inventory management system is composed of following:
- Customer database
- Supplier database
- Sales database
- Inventory database
- Purchase database
- Transaction database

These data stores are responsible for maintaining all records of the system and maintaining data security. Information is available to the authorised user who will request for it.
In the above discussion we have explain about level 0, 1, 2 data flow diagram (DFD) for inventory management system. Each level has its own importance.