Define services corresponding to Domain-Driven Design (DDD) subdomains.

 DDD refers to the application’s problem space - the business - as the domain. 

A domain is consists of multiple subdomains. 

Each subdomain corresponds to a different part of the business.

Subdomains can be classified as follows:

Core - key differentiator for the business and the most valuable part of the application

Supporting - related to what the business does but not a differentiator. 

These can be implemented in-house or outsourced.

Generic - not specific to the business and are ideally implemented using off the shelf software