Need help with this question ( about E-R diagram )

[Learnereto]

This is a question which consist of a scenario with a given E-R diagram that need to be corrected by applying the given requirements in the scenario and i have posted it here as points and i have posted my answer ( as a picture). i really hope someone could tell me if i hava mistake on it or not.



A center called ITARD do employing for Researchers(R), Research Assistants (RAs) and Administrators (A).

The information that should kept for each employee are [ FName , MName , LName , Bdate , Gender , Address , Phone , Mobile , date of joined , date of left]

The information that should kept for each Project are [ Title, its description , start date , planned end date , actual end date , total planned budget , the PI ( principle investigator) ,The RAs and whom each is assigned]

These are the requirement that should be represented in the E-R diagram:

1-At the same Time, Each researcher may work on one or more active research projects.

2- A researcher not working on any active research projects may engage in any number of unsponsored research project with or without collaboration from the other researchers and in each case , they are not aided by any RA.

3-Researchers can collaborate on research projects, but there must be one PI (principle Investigator) designed each project.

4-Each Research Assistant (RA) is assigned to work on one or more projects.

5-Each (RA) is supervised be exactly one researcher for each research project the RA works on.

6-Since (RAs) are hired on research projects, no RA can be left without assigned tasks in one or more research projects.

7-Each project must be administered by one Administrator. Additionally, each administrator is supervised by one supervisor (another administrator)


i have solved this questions and I need to be sure of my solution if there is any mistake, if someone discoved mistakes please replay .
please take a look on the photo of the ERD below.

<img src="http://imgur.com/LV1ry.png" alt="" title="Hosted by imgur.com" />

regards

 

[stopher]

Welcome to the forum.

I'm guessing this is a student exercise so forgive me if I don't give you a solution.

Also, be aware that E-R diagrams have varying notations so what I suggest hear might not be 100% what you've been taught. However, the notation that you are using appears to be the one I am familiar with.

The first thing I notice is that you have not really addressed the statement:
"The information that should kept for each employee are [ FName , MName , LName , Bdate , Gender , Address , Phone , Mobile , date of joined , date of left]". I would expect to see this represented by an entity. I would expect to see the the different types of employees (administrator, supervisor, researcher) as sub-entities of Employee. Diagrammatically this would be three boxes inside a Employee box. I suspect sub-entities will be needed elsewhere also.

You seem to have lost a mandatory/optional blob in one of the participate relationships.

For point 2, how have you identified that researchers not working on projects can work on unsponsored projects. The way the model looks at the momemt, a researcher could work on both.

I don't think you've addressed point 3 in your model.

The blob and relationship title missing from the "researcher supervises a research assistant" relationship. Also, consider the case if an assistant is working on two projects. How have you modelled that this assistant must have two related supervisors?

I don't think point 6 is in your model.

So I think you've got a few changes to make yet.

hth
Chris

 

[Learnereto]

Stopher,

Thank you very much for the time you spent on replaying to my question.

I read your notices and I tried my best to recognize the mistakes in the ERD and I think they should be corrected as the follwing:

1- project - Researcher in the principal Investigates relationship,

( Each researcher (Investigators ) may principle Investigates 0,1 , M Projects
but each project must be principal Investigated by 1 researcher (principal Investigator)) .

2- Recursive relationship in the Researcher relation.

(each researcher (principal Investigator) may heads 0,1, M researchers but each researcher (other Investigators) must be headed by a researcher ).

3- Researcher - Research Assistant (supervised by relationship) .

(each Research Assitant must be supervised by 1 Researcher but each Reseacher may supervises research Assistants).

4- Researcher - Unsponsored Projects (Participates relationship).

(Each researcher may participates in 0,1,M Unsponsored Projects but Each Unsponsored Project must be participated by a researcher) depending on an Assumption in the given CDM that no collaboration in the Unsponsored Project.

I am not so sure of the last one but it is te best that I got for now, also I didn't want to make it optional to optional participation condition between the researcher and the Unsponsored Projects because I will need to make a new Relation to link them both.

I wish to hear from you soon, Thanx alot once again.