Course Platform Data Model

Specify entities and relationships for courses, lessons, enrolments, progress and access rules.

Create specify entities and relationships for courses, lessons, enrolments, progress and access rules.

Use these inputs:
- course structure: [course structure]
- learner roles: [learner roles]
- access model: [access model]

Return the finished result first. Then add a short assumptions note and three practical improvements. Do not invent facts, research, testimonials or results. If one essential detail is missing, use the safest reasonable assumption and label it instead of restarting with a long questionnaire.