XI system as a business system in XI SLD?

Hello,

I recently saw an XI SLD where not just the R/3 business systems, but also the XI system itself was configured as a business system. Is there any need to have the XI system itself in its own SLD as a business system?

If yes: Do I also have to configure transport target for the XI business system (e.g. from XI dev to XI prod)?

Thanks,

Christoph