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Embedded systems cover a wide variety of devices and applications. Seemingly, each embedded system is different from other embedded systems. After all, the system controlling a microwave oven has virtually nothing in common with the system in a calculator, an airplane flight controller, or a car's engine controller. However, is there a way to look at embedded systems from a generic viewpoint? Put another way, are there parts of all embedded systems that are common whatever the purpose or function of the individual devices? What exactly do the microwave oven controller and a vehicle's engine controller have in common? The design of a “layers-type” model representing embedded systems development arose from asking just such questions. Starting with the background of the OSI Network Model, where all functions of network communications fit within one of seven layers, we began to ask if a similar structure could serve to describe embedded systems.

The accelerating cost of developing the electronic content of the typical vehicle is in part due to the cost of software development for these electronic modules. Software development costs for many projects are difficult to predict accurately, and even more difficult to control. A number of software development methodologies have been published and are followed with mixed success. All place great significance on the generation and management of the requirements for the software. This paper provides a basic definition of what proper requirements should be, discusses the importance of proper requirements in software development, and compares several approaches to the generation and the management of requirements. Finally, the paper suggests an approach to managing ever-changing ‘real-world’ requirements.