```mermaid
erDiagram
    Exercise 1 .. 0+ Equipment : uses
    Exercise 1 -- 0+ WorkoutItem : "provides data for"
    Workout 1 .. 0+ WorkoutItem : collects
    Workout 1 .. 0+ WorkoutSession : "starts"
    WorkoutItem 1 -- 1 WorkoutSessionItem : "provides data for"
    WorkoutItem 1 -- 0+ WorkoutItem : "collects"
    WorkoutSession 1 -- 1+ WorkoutSessionItem : collects
    ContentView 1 -- 1 WorkoutSession : "holds onto"

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