Entities are the things flowing through the sequential processes in the model (e.g. patients, telephone calls, blood test results).
Generators are the way in which entities enter the model and come into being (e.g. brought in by paramedics, self-presenting). Sometimes you will only have one generator, but some other times you will need multiple generators.
Inter-arrival Times specify the time between entities being generated (arriving in the model). You may have different inter-arrival times for different generators.
Activities/Servers represent the activities that happen to entities (e.g. triage, treatment, ward admission).
Activity/Server Time represents the amount of time it takes for an activity to happen to an entity.
Resources are required for activities to take place and may be shared between activities (e.g. nurse, doctor, receptionist, bed).
Queues are where entities are held until an activity has capacity and the required resources to begin.
Sinks are how entities leave the model. Like generators, you can have more than one (e.g. Out, Died).
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