looking best notation for UML Class diagram

Question

I have the following problem to resolv. Given the following UML diagram:

I need to complete the diagram doing the following steps:

a) When an employee has a skill, the relationship between the employee and the skill shows years of experience.

b) A worker may have another employee as a manager and a worker who is a manager must manage five or more workers. As a manager, you can determine which workers he manages, but a worker can not determine who is his manager.

c) An activity can have a maximum activity precedent and any number of upcoming activities. Using these roles, we can show how the activities are arranged. Given an activity, you can only determine their own activities (if you have), but not what your previous activity (if any).

d) A worker is not simply associated with a set of skills, but a worker has skills. In particular, every worker should have three or more skills, and any number of employees can have the same ability.

e) A project is not simply a set of activities associated with, but contains a project activities. Specifically, a project must have one or more activities, and activity must belong to exactly one project.

f) Projects and activities are a specific type of job.

My solution is shown in the following picture, but because I am new in this I would like to check if is fine.

Thank you in advance!

Answer 1

Looks good in most parts. Honestly I don't understand the later parts of c)

Your -boss relation is wrong. Your Northern Koreans should not have a private known boss. Instead there's only the other way around and the boss has - let's call them - -slaves. If you put in a private -boss it actually means that the slave can navigate to its private boss which is explicitly not wanted. Only the boss shall know the one he's responsible for. So actually the object itself is the boss object. As a thought, since only the boss should have those 5 employees, it could be an idea to create a separate boss object like this:

Note that this might also have drawbacks since Boss is now actually a different object than Employee, but it seems to fit the requirements.

Point f) seems to call for a generalization. So you would need a generalization towards SpecificJob. This would be an arrow with open triangle, not the one you used:

This actually reads Project and Activity are specific kinds of Job as they both inherit from the latter.