Develop a simple database for a construction design firm using the following instructions:

The database can be used by multiple projects. A project is composed of design items. The organization has several departments: Architectural Department, Structural Department, Environmental Department, and Land Development Department etc. One or more departments may participate in one project. Any department can participate in several projects. A department may employ many employees but each employee may be employed by one department. Each department is managed by only one of the employees. The organization has a training program in which an employee may manage (or train) many other employees and each employee is managed (or trained) by one employee. During the implementation of a project, project documents (reports or drawings) are generated. One document is produced by one or many employees and an employee can produce several documents. A design item consists of multiple documents. The developed database should provide the users with name of the project, its start-date, its enddate, contract price, design fee of each design item, involved departments, basic information of involved employees, the number of employees in the organization, the number of Licensed Professional Engineers etc.

Develop an Entity-Relationship diagram based on the instructions above. Your E-R diagram should have several weak entity sets, one relationship with roles, many types of relationships (one-to-many, many-tomany, one-to-one) and one entity set that contains subclasses in an isa relationship. Please specify any additional assumptions you are making while building this E-R diagram.