Model E.R - Correct?

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Model E.R - Correct?

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#1 by (1 votes)

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Hello, I will develop a project for my computer technician course and I am having difficulty with an E.R. This is the following, this is the description of the project, but I will ignore the attributes of the entities ok? I will only mention the participation of each one in the system.

It is a system of ticket sales, where the user can register and after that will enter the system, with his login and password. Upon entering the system, he will have access to his tickets (purchased by him), to his events (in which case he would sell the ticket, he would be responsible for such an event) and also to change his data, obviously. The purchase will be done by card (simulation, in case). It can buy several tickets and the ticket can be sold to several users, since for an event there may be certain amount of tickets. That's basically it. The rest is visual. The site would be very similar to ingresse.com (I do not know if I can put links here).

I did one, but I think it's wrong:

modelo-relacional entidade-relacionamento

asked by anonymous 24.05.2016 / 01:57

1 answer

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score 1 · Accepted Answer

The conceptual model is the model with the highest level of abstraction in a Database. So some questions that seem simple and logical to those who are doing turn out to be difficult for those reading. Anyway, I'll try to help based on the information presented (both in the text and in the template).

Most of the text described is not exclusively about modeling, but rather about something more for implementation / coding. Ex: when entering the system it will have access ...; the user can change their data ...

It is important to take the information that deals with the relationship between entities, so we would get the data needed for the conceptual model. Ex: the user can buy several tickets; tickets can be sold to multiple users.

Because we do not have all the information, it is impossible to tell if the model is right or wrong (or whether it should have an aggregation or not), but I will read the displayed model if you perceive some information that does not match your system, this part of the model needs to be revised. The points that you judge "interesting" I will call Point of Attention, not necessarily they are right or wrong, as they depend on the purpose of your system.

Perform 1.1 A user can perform many events. 1.2 An event must be performed by one and only one user (point of attention: according to the model presented, your system does not contemplate the realization of an event by two users or more.)

Own 2.1 An event must have many tickets. (Attention point: according to the model presented, we can not have an event without it having tickets). 2.2 A ticket must be owned by one and only one event.

Buy Now 3.1 A user can buy many tickets. 3.2 A ticket can be purchased by many users.

I believe that the conceptual model, according to what you have informed, may also receive the relationship Sell, between the User and Ingres entities. For an Aggregation to be inserted in the model, we would have to change not only the wording of the text, but also the logic that was presented in the model.

I hope very much to have helped, as much as possible.