Building an e-commerce site: the key questions

When building an e-commerce site, there are several components whose implementation is strongly domain-specific. That is, every site will have different requirements for how such a component should operate. As such, these components cannot easily be modelled using a generic system - no configurable system will be able to accurately capture all the domain-specific behaviour required.

The design philosophy of Oscar is to not make a decision for you here, but to provide the foundations upon which any domain logic can be implemented, no matter how complex.

This document lists the components which will require implementation according to the domain at hand. These are the key questions to answer when building your application. Much of Oscar’s documentation is in the form of “recipes” that explain how to solve the questions listed here - each question links to the relevant recipes.


What are your product types?

Are you selling books, DVDs, clothing, downloads, or fruit and vegetables? You will need to capture the attributes of your product types within your models. Oscar divides products into ‘product classes’ which each have their own set of attributes. Modelling the catalogue on the backend is explained in Modelling your catalogue.

How is your catalogue organised?

How are products organised on the front end? A common pattern is to have a single category tree where each product belongs to one category which sits within a tree structure of other categories. However, there are lots of other options such as having several separate taxonomy trees (e.g., split by brand, by theme, by product type). Other questions to consider:

  • Can a product belong to more than one category?

  • Can a category sit in more than one place within the tree? (e.g., a “children’s fiction” category might sit beneath “children’s books” and “fiction”).

How are products managed?

Is the catalogue managed by an admin using a dashboard, or though an automated process, such as processing feeds from a fulfilment system? Where are your product images going to be served from?

Pricing, stock and availability

How is tax calculated?

Taxes vary widely between countries. Even the way that prices are displayed varies between countries. For instance, in the UK and Europe prices are shown inclusive of VAT whereas in the US, taxes are often not shown until the final stage of checkout.

Furthermore, the amount of tax charged can vary depending on a number of factors, including:

  • The products being bought (e.g., in the UK, certain products have pay no VAT).

  • Who the customer is. For instance, sales reps will often not pay tax whereas regular customers will.

  • The shipping address of the order.

  • The payment method used.

Recipes: * How to handle US taxes

What availability messages are shown to customers?

Based on the stock information from a fulfilment partner, what messaging should be displayed on the site?

Do you allow pre-orders and back-orders

A pre-order is where you allow a product to be bought before it has been published, while a back-order is where you allow a product to be bought that is currently out of stock.


How are shipping charges calculated?

There are lots of options and variations here. Shipping methods and their associated charges can take a variety of forms, including:

  • A charge based on the weight of the basket

  • Charging a pre-order and pre-item charge

  • Having free shipping for orders above a given threshold


Which shipping methods are available?

There’s often also an issue of which shipping methods are available, as this can depend on:

  • The shipping address (e.g., overseas orders have higher charges)

  • The contents of the basket (e.g., free shipping for downloadable products)

  • Who the user is (e.g., sales reps get free shipping)

Oscar provides classes for free shipping, fixed charge shipping, pre-order and per-product item charges and weight-based charges. It is provides a mechanism for determining which shipping methods are available to the user.



How are customers going to pay for orders?

Often a shop will have a single mechanism for taking payment, such as integrating with a payment gateway or using PayPal. However more complicated projects will allow users to combine several different payment sources such as bankcards, business accounts and gift cards.

Possible payment sources include:

  • Bankcard

  • Google checkout

  • PayPal

  • Business account

  • Managed budget

  • Gift card

  • No upfront payment but send invoices later

The checkout app within django-oscar is suitably flexible that all of these methods (and in any combination) is supported. However, you will need to implement the logic for your domain by subclassing the relevant view/util classes.

Domain logic is often required to:

  • Determine which payment methods are available to an order;

  • Determine if payment can be split across sources and in which combinations;

  • Determine the order in which to take payment;

  • Determine how to handle failing payments (this can get complicated when using multiple payment sources to pay for an order).

When will payment be taken?

A common pattern is to pre-authorise a bankcard at the point of checkout then ‘settle’ for the appropriate amounts when the items actually ship. However, sometimes payment is taken up front. Often you won’t have a choice due to limitations of the payment partner you need to integrate with, or legal restrictions of the country you are operating in.

  • Will the customer be debited at point of checkout, or when the items are dispatched?

  • If charging after checkout, when are shipping charges collected?

  • What happens if an order is cancelled after partial payment?

Order processing

How will orders be processed?

Orders can be processed in many ways, including:

  • Manual process. For instance, a worker in a warehouse may download a picking slip from the dashboard and mark products as shipped when they have been put in the van.

  • Fully automated process, where files are transferred between the merchant and the fulfilment partner to indicate shipping statuses.