Core: The main focus area for the business. This is what provides the biggest differentiation and value. It is, therefore, natural to want to place the most focus on the core subdomain. In the retail example, shopping carts and orders might be the biggest differentiation—and hence may form the core subdomains for that business venture. It is prudent to implement core subdomains in-house, given that it is something that businesses will desire to have the most control over. In the online retail example, the business may want to focus on providing an enriched experience for placing online orders. This will make the online orders and shopping cart part of the core subdomain.

Supporting: Like with every great movie, where it is not possible to create a masterpiece without a solid supporting cast, so it is with supporting or auxiliary subdomains. Supporting subdomains are usually very important and very much required but may not be the primary focus of running the business. These supporting subdomains, while necessary to run the business, do not usually offer a significant competitive advantage. Hence, it might even be fine to completely outsource this work or use an off-the-shelf solution as is or with minor tweaks. For the retail example, assuming that online ordering is the primary focus of this business, catalog management may be a supporting subdomain.

Generic: When working with business applications, you are required to provide a set of capabilities not directly related to the problem being solved. Consequently, it might suffice to just make use of an off-the-shelf solution. For the retail example, the identity, auditing, and activity tracking subdomains might fall in that category.