I was looking at the conceptual model diagrams, I saw some that contains the Attributes and Entities like this:
AndothersthatonlyhavetheEntity:
Which model is correct? or are the two of you?
Is it necessary to identify attributes in Conceptual ER? or can I just have Entities and relationships between them?
If you need to declare Attributes, what do you do when an Entity has a huge amount of Attributes, like 30 or more?
There are various diagram notations , each with its own characteristic. None is wrong. But each can be more appropriate than another. It depends on the intent you want to demonstrate.
Particularly I think the conceptual model should be quite simple and leave the details for the logical model that has a notation easier to organize the details.
In general, when you place attributes on entities in the conceptual model, you place only what is strictly necessary to help you understand relationships or other fundamental things. But nothing prevents it from putting everything. Both are correct.
Some authors consider it wrong to place attributes in the conceptual model. Others say they can, as long as they do not use technical terms.
So who's right? Do what is helpful to you and do not worry if someone says it is right or not. The important thing is to have something that helps. There are people who need the conceptual, logical and physical model, in great detail. There are people who only turn to the physical.
It is possible to have a separate document that supports the conceptual diagram in more detail.
Remember that the conceptual model is not very technical, it should be easy to read by a layman in computing. This is the main difference of the conceptual model and the logical one that is already a bit more technical, but still a bit abstract.
A sophisticated data dictionary can help map this. Unfortunately there are no good tools in the market for this.
a) the objects that make up reality,
b) the types of information or characteristics you want to know about the objects that make up reality and
c) how these objects interact with each other.
In this way, Entity-Relationship Model is composed of three concepts: Entity, Attribute and Relationship . The objects that make up reality are Entities. The characteristics that one wishes to know about the objects that compose the reality are the Attributes. The way objects interact with each other is the Relationship.
So your first two questions lead me to the same answer: Yes, both models are correct, the first one being the best. The more detail you add in a correct and coherent way to the model as taught by theory, the better the understanding / understanding / ease of development will be. Of course, any additional effort should match within a cost-time-result line, but I will not go into those details that run the gamut ...
As for the attribute , I learned that:
a) Identification : The identification of each attribute must be composed of a singular noun and, if necessary, one more qualifier that characterizes it. Capital letters must be used. For example: NAME, DESCRIPTION, DATE OF BIRTH
b) Definition : Each attribute should be given a brief description of its meaning to the Organization. In addition, the description of an attribute must be complemented with a local or global data type that characterizes it. For example: REGISTRATION NUMBER (INT, 05).
That is, if these attributes are with many characters it is because there is something that contradicts the item A of our theory. Therefore, it would be better to review their identification.
