Section 6. Relevant Facts and Assumptions

6. Relevant Facts and Assumptions

6a. Facts

Relevant facts are external factors that have an effect on the product but are not covered by other sections. They are not necessarily translated into requirements but could be. Relevant facts alert the developers to conditions and factors that have a bearing on the requirements. For example, it may be that the IceBreaker product's specification would contain relevant facts:

Salt (NaCl) de-ices down to 6°C. Calcium chloride (CaCl) de-ices down to 15°C.

One ton of de-icing material treats three miles of single-lane roadway.

These facts must be taken into account when scheduling trucks to treat freezing roads. Note that they are not requirements as such, but have a strong effect on the outcome of the product.

Relevant facts are usually discovered when you are trawling for requirements, and particularly when you are discussing the business rules with your users. The background information given by the relevant facts section is required reading for new people on the project.

6b. Assumptions

The assumptions you write in this section are those being made by the project team. The intention is to alert management to factors that might affect the product. The assumptions usually focus on the intended operational environment of the product, but may relate to anything that could, if the assumption does not come true, have a detrimental effect on the success of the product.

Roads that have been treated will not need treating for at least two hours.

Road treatment stops at county boundaries.

By stating these assumptions, the analyst says to the stakeholders, "Look at these. I am proceeding on the basis that these assumptions are true. The product that I specify assumes that they are true. If the product is not to stop road treatment at county boundaries, then please let me know right now."

Sometimes other products may be undergoing development at the same time as your product, and their delivery failure will affect your product. Similarly, you may be making assumptions about the performance or capacity of some as-yet-untested product. If that product does not perform as you assume it does, your product will be adversely affected.

Road Engineering's Apian system will be available for integration testing before November.

The treatment trucks being built will be capable of operating at speeds up to 40 mph. They will have a material capacity of two tons.

You may make assumptions about interfaces between the product under development and existing products. For example, the IceBreaker product must interact with the weather stations. These stations are being developed by an outside organization. Obviously, if there are variations in the way that they transmit their information, then the IceBreaker product will not work as planned.

The Bureau's forecasts will be transmitted according to its specification 10037 issued by its engineering department.

Also, you may write assumptions about the availability and capability of bought-in components, the operational environment of the product, the capabilities of the development language, or anything else that will be used by the product.

It is anticipatedin fact, it is necessarythat all assumptions will have been resolved by the time the product is released.