The environment is what a system interacts with. Technically a system is influenced by its environment and causes changes in the environment.

Environment Diagram

Environment Diagrams show systems in the environment interacting with the subject system.


The environment is everything that interacts with a system, that is not part of the system. Typically the designer of the subject system does not care about interactions of actors in the environment. With machines that humans use, the human is usually defined as part of the environment.

There are other systems out in the environment. We distinguish the system of interest from the other systems by referring to the Subject System. The Subject System is the one being designed. All the other systems in the environment are called Actors.


A variant of the environment diagram is called a domain diagram. A domain is similar to the environment but has a slightly larger scope. The domain can consist of things that interact with each other and the environment. The domain diagram will show these interactions and so their implications are often considered when designing the subject system.

For example; the sun is in the environment and beats down on the mower operator which is also in the environment. A designer might consider the attachment of an umbrella to the mower to shade the operator from the sun.

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