In the parking domain diagram, we use geometric shapes to represent different elements, such as curbs and cars, to visually convey their status and relationships. Here's how each visual element is encoded:

1. **Shapes**:
   - **Rectangles**: Represent curbs. Each curb is a medium-sized rectangle, indicating a parking spot where cars can be parked.
   - **Circles**: Represent cars. Each car is a small circle within or behind a rectangle, indicating its parking status.

2. **Colors**:
   - **Green**: Indicates a "clear" status. For cars, it means the car is free to move. For curbs, it indicates that the curb is empty and available for parking.
   - **Red**: Indicates a "not clear" status. For cars, it means another car is double parked behind it, preventing it from moving. For curbs, it means the curb is occupied.

3. **Text Labels**:
   - Each object (curb or car) is labeled with its identifier (e.g., curb_0, car6) and its status (e.g., "clear" or "not clear"). The label is placed inside the shape to ensure clarity and readability.

4. **Arrows**:
   - Arrows may be used to represent possible movements or actions between cars and curbs, indicating permissible actions as per the domain rules.

5. **Legend**:
   - A legend is included to map colors to their meanings (e.g., green for clear, red for not clear). This ensures that the diagram is self-explanatory.

6. **Layout**:
   - Objects are positioned in a grid format, with curbs arranged horizontally from left to right. Cars are placed inside or behind curbs based on their parking status. This spatial arrangement helps to depict the current parking configuration clearly.

7. **Text Contrast**:
   - To ensure readability, text labels and statuses are in high-contrast colors against their backgrounds. For example, black text is used against light backgrounds, and white text is used against dark backgrounds.

This encoding scheme allows viewers to quickly understand the parking configuration, the status of each car and curb, and the potential actions that can be taken within the domain.