Real_Estate_Developer
| id | name | contact_info |
| 1 | Company A | +123456789 |
| 2 | Company B | +987654321 |
Contractor
| id | name | specialty | license_number |
| 1 | Contractor X | Concrete Work | LX001 |
| 2 | Contractor Y | Plumbing | LY002 |
Development_Project
| id | project_name | developer_id | contractor_id |
| | (→ Real_Estate_Developer.id) | (→ Contractor.id) |
| 1 | High Rise Building | 1 | 1 |
| 2 | Residential Complex | 2 | 2 |
Project_Milestone
| id | milestone_description | start_date | end_date | development_project_id |
| | | | (→ Development_Project.id) |
| 1 | Foundation Completed | 2023-01-01 | 2023-01-10 | 1 |
| 2 | Framing Started | 2023-01-11 | 2023-01-20 | 1 |
Materials
| id | material_type | quantity | unit_price | contractor_id |
| | | | (→ Contractor.id) |
| 1 | Reinforcement Bar | 500 | 10 | 1 |
| 2 | Pipes | 300 | 8 | 2 |
Employee
| id | first_name | last_name | position | contractor_id |
| | | | (→ Contractor.id) |
| 1 | John | Smith | Site Supervisor | 1 |
| 2 | Jane | Doe | Engineer | 2 |