```mermaid
erDiagram
    Exercise 1 .. 0+ Equipment : uses
    Exercise 1 -- 0+ WorkoutItem : "provides data for"
    Workout 1 .. 0+ WorkoutItem : collects
    Workout 1 .. 0+ ViewModel : "provides data for"
    WorkoutItem 1 -- 1 WorkoutSessionItem : "provides data for"
    WorkoutSession 1 -- 1+ WorkoutSessionItem : collects
    ViewModel 1 -- 1+ WorkoutSession : "creates, starts"

    Exercise {
        string name
        Equipment[] equipment
    }
    Workout {
        string name
    }
    WorkoutSession {
        Workout workout
        time workoutSessionDuration
    }
    WorkoutItem {
        Exercise exerciseData
        int plannedReps
        double plannedValue
    }
    WorkoutSessionItem {
        WorkoutItem exerciseData
        int actualReps
        double actualValue
    }
    ViewModel {
        Workout workout
        WorkoutSession workoutSession
    }
```