This is a custom ERP for a small trailer repair business.

This application includes two abstract models for Transaction and Category. The Order model is common to Inventory and Services. Orders can be of type purchase or sell.

The main model in this application is the Product which can be either a part or a consumable that can be stored and counted. The Unit model allows to store, buy and sell products in different measurement unit, handling automatically the unit conversion. Units are divided into magnitudes (Quantity), such as mass, distance etc. The base unit for conversion is always from the ISU.

The ProductCategory is used for filtering in the user interface. The ProductTransaction represents the purchase of service transaction within a given Order. There can be several PriceReference for a product, holding the link and price reference from and online store.

The ProductKit storage a set of products and services that are usually included together in service orders. The KitElement creates a link between a Product and the ProductKit it belongs to. The KitService creates a link between a Service and the ProductKit it belongs to.

The main model in this application is the Service, which includes a description and a suggested price for a given labor. The ServiceCategory is used for filtering in the user interface. The ServiceTransaction represents a particular labor included in a service Order.

Each Order has one or several Payment associated when completed. PaymentCategory divides payments into payment methods.

The PendingPayment accounts the debt payment for a given client.

The Expense model accounts for the Third Party Services required for the given service Order.

The UserProfile adds the avatar image and the phone number to the standard django user model. This model stores the information of the users that can access into the system: Admins or Mechanistic.

An Associated can be either a client or a provider. Service orders can be issued to a client or a Company. The abstract model Contact defines the fields that are common to Company and Associated. Purchase orders are linked always to a provider*.

The Equipment model is the abstract model that defines the field that are common to Vehicles (mostly trucks) and Trailers. Equipment can be linked into service orders but it is not required.

The Cost model is the main model in this application. Costs are discounted to compute the profit in a period. The CostCategory is used for filtering in the user interface.

This is a complete representation of the models and their relations.