Use a more descriptive name by default

[graven]

"db" is not a descriptive name. Let's call it "MySQL".

[dieu]

db it is a generic name, I think use "mysql" in interface isn't good practice.

[graven]

Say Postgres component comes out. Now I cannot add it to my instance because I already have a "db" component.

Instead, PetClinic should specify a dependency on the interface and the environment policy will dictate which implementation to use (R24 and beyond).