Requirements

The goal of this project is to provide a universal tool that answers the question "who owes whom?" in the context of a social group of people. It has to fulfil the following requirements.

Simplicity

The tool must be simple to use. This is the ultimate requirement. It should guide the user through one unique short process independent from the number of people involved and the number of transactions.

Ergonomy

The tool must provide a maximum level of comfort and require a minimum of user interactions. It must be responsive and fluid.

Especially, entering expenses must be similar and as natural as filling a spreadsheet.

Versatility

The tool must be able to manage the following situations:

• recurrent shared expenses inside a non-constant group of people, e.g living with roommates,
• punctual shared expenses, e.g sharing expenses during a week-end with friends,
• lending or borrowing money to someone,
• different shares of an expense.

In any case, versatility should interfere with simplicity. However, if the complexity of a situation requires extra steps in the process, those steps should remain optional and transparent to the other situations.

Traceability

The user must be able to check easily by himself over his whole history, all the calculations made by the system.

Efficiency

The tool must be able to simplify the debts inside a social group to the minimum set of transactions possible.

Free and safe

The service must remain totally free of charge. None of the users' data should be communicated to anybody unless requested by the user, nor used for any other purpose than what the service is supposed to do. A user must be able to delete all his data.