I have been using VP for about a month now and I have still yet to figure out the difference between the conceptual, logical and physical data models as implemented in Visual Paradigm. Aside from it being a selection in the diagram’s properties, and a change in the entity’s color, I cannot see any practical difference between the 3 models.
Ordinarily, a CASE tool, System Architect for example, lets you use one diagram for all three purposes by changing the view of the model. For example, in conceptual mode, only the entity’s logical name is shown. For the logical view, the entitys and columns are displayed using logical names. And lastly, the physical model, the actual table and column names as well as the column attributes (size, type, etc.) are displayed.
In VP it appears that you would have to create 3 separate diagrams to accomplish the same results. Is this correct? Can anyone shed some light on this subject for me please?
Different CASE tool vendor have different approach on handing the conceptual, logical and physical data models. You are correct that VP using different diagrams for conceptual, logical and physical data models.
In VP, actually conceptual, logical and physical data models are having their own set of ER models. They are related to each other using the Model Transitor. The Model Transitor establish the trace between different models. One of the typical case is you create a conceptual model with some entities, then transit to logical model and do some enhancement. The Model Transitor helps to to keep track on the transformation of the ER model.
Only the physical model will be involved in database generation.
Thank you the speedy response and help in this matter.
Then my suspicions were correct: I need to create 3 separate models. Our use of the 3 models is as follows:
Conceptual - Communicates the ‘concept’ of the data requirements as an undefined collection during discovery in the analysis phase of the development process.
Logical - an embellishment of the above model by the addition of the logically needed pieces of information that further define (and refine) the conceptual entity.
Physical - Contains actual table and column names, along with the other required column properties (type, size, primary key inclusion, foreign key designation, etc) needed to generate the actual database within the DBMS.
Actually you don’t need to create 3 separate models. Assume you start from conceptual model, you can simply select conceptual model when create ERD (see data_model.png). After you create the conceptual model, you can right click on your ERD and select Transit to Logical/Physical ERD. This will create a new ERD based on your conceptual model (all the entity are linked with transitor automatically). And you can then simply modify the new ERD, with all the trace established automatically.
