3. Missions, functions and failures of a system and its components

3.1 Missions and functions

An operational safety study necessarily involves an exhaustive analysis of the various phases of operation, using precise terms such as the missions and functions performed by an asset. It is particularly important to define the notions of function and mission. These definitions vary widely from one business sector to another, and from one country to another. The missions and functions of an entity derive directly from the definition and specification of its operational requirements:

• What are the operational requirements, and how will the entity be used?

• Where will the entity be used?

• How long will the entity be used?

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