Sparx Systems Forum

Enterprise Architect => General Board => Topic started by: peter king on November 22, 2009, 04:07:52 am

Title: First is it class Diagram or ERD?
Post by: peter king on November 22, 2009, 04:07:52 am

Hi friends,

In project should PM decide to start designing the DB using ERD first or class diagram first?

The reason i prompt this qestion becauase in either way we could map each diagram to the other?

thanks

Title: Re: First is it class Diagram or ERD?
Post by: Paolo F Cantoni on November 22, 2009, 10:50:09 am

Quote

Hi friends,

In project should PM decide to start designing the DB using ERD first or class diagram first?

The reason i prompt this question because in either way we could map each diagram to the other?

thanks

It depends on what you expect to use the DB for...

If you intend the DB to me merely a persistence of your programmatic classes then start with the classes.

If, however, the DB represents a proper data model of the domain of the the application (and possibly even more) then you should start with the ERD.

In particular, you should initially model all domain concepts without regard to the application to obtain the correct representation of the domain and then overlay the application specific data.

HTH,
Paolo

Title: Re: First is it class Diagram or ERD?
Post by: peter king on November 22, 2009, 02:23:14 pm

thanks paolo! :)

Title: Re: First is it class Diagram or ERD?
Post by: Geert Bellekens on November 23, 2009, 07:58:37 pm

We tend to see the classes (in a class diagram) as the logical representation where the tables (in an ERD) would be the physical representation of the data aspect of our application.

Geert