System Definition

What

System Definition - summary of the new system.

How

The dish

System definition

Ingredients

• A Rich Picture
• Stakeholder interests
• General system requirements

Process

Summarise the present understanding of the IT system-to-be in a few sentences (max. ¾ of a page is needed). Try to integrate the customer's main values into the system definition.

It is recommended to prepare more than one system definition with different philosophy views and let the customer choose the one that fits best into his expectations.

Why

The system definition is a short description of the system-to-be that is going to be developed. It is the first description of the system according to the developer's understanding of the requirements. It follows the rich picture which has been drawn in cooperation with the customer.

The system definition is a good way to communicate to the customer how we have understood the system-to-be. Remember the development process is still in its early stages and the developer still needs to acquire a basic understanding of which type of system the customer wants. By describing the requirements in a relatively short summary (max. ¾ of a page), the developer can communicate his or hers perception of the system.

It is important to incorporate the customer's values in the product, therefore the system definition can be written in several versions each differing by the way you express the customer's values and thereby the philosophy in the product.

The customer's values may not be clearly stated and there may be different employee values at the the customer's company. The sales department may have different values and opinions about the new product than the research and development (engineering) department. The management may have values that differ from all other departments. Sales may want a product that have some smart easily saleable functions that may not be of any technical value for the engineering people who want a product with high technical functions. The management's interest is mainly a saleable product that solves the problem at the lowest possible cost.

Therefore, the developer should perform an analysis of the different parties interested in the project - the so-called stakeholders. The analysis can provide the developer with information about the different kinds of interest in the project. This knowledge should be kept in mind through out the lifetime of the project.

Example

Proposal #1 - technical:

The system controls the heating installation in houses with own oil burner, combined hot-water tank (can produce hot water from both electric power and hot water from boiler) and electric sun power cells.

The temperature in the heating installation is controlled in the motor controlled mixer so the temperature sent to the radiators matches the exact heating need in the house. The expected heating need is calculated based on temperature sensors placed outdoor and indoor. A temperature sensor is also placed after the mixer enabling measurement of the supplied water's temperature.

The temperature in the boiler is controlled in the interval 30 to 70 degrees Celsius depending on the need for heating and hot water.

Oil burner and pumps will be switched off if there is no need for heating in the house (e.g. in summertime). Electric heating in the hot water tank will be switched on.

The system can be set in low consumption mode when the house is not occupied for shorter or longer periods.

If the electric power produced in the sun power cells exceeds 1,5 KW, electric heating of the hot water will be prioritised.

The system can be controlled through a web interface where the house owner can set expected room temperature, lower and upper boiler temperatures, and limits for switching into electric hot water production. The house owner can monitor all temperatures and electric production from the sun power cells on-line. The monitoring includes instant values as well as historic measurements.

Proposal #2 - automatic optimising:

By controlling the temperature in the heating installation and prioritising sun power in production of hot water, the energy consumption is optimised in this web-controlled energy optimising system.

The house owner can from any web-enabled computer safely both control and monitor historic and instant values in the energy production system. The house owner can program periods with low energy consumption when leaving for vacation.

By using the heating installation's motor controlled mixer, the temperature of the hot water is controlled to match the exact required room temperature. By measuring the temperature both outdoor and indoor, the system calculates the required temperature needed to hold the room temperature constant, thereby maximising the comfort. Oil burner and pumps will automatically be switched off when no need for heating is required.

See the stakeholder analysis to see who would select Proposal #1 and who would select Proposal #2.