What a great topic!
tl;dr To answer your direct question, you'll only define things as Technical Services if you are using Event Management, as you may want your Event Management dashboards to roll up for IT visibility, whereas the Business Services should be customer-facing and be broken down into Service Offerings. In your example Exchange and Active Directory should both be Service Offerings, so you can track availability, slas, outages, etc.
Within ServiceNow you have a couple of layers, so it's first important to understand those artifacts and how they're utilized:
- Configuration Item: Any item that is being tracked within your CMDB and for which you have configuration information. This is the lowest layer in a service-aware CMDB. Conceptually, this is anything with an IP address (though obviously documents and applications could be CIs and won't have them, but this is just a concept). See here: Configuration Management Database
- Business Service: Work or goods that are supported by an IT infrastructure. Within ServiceNow we then break these down into different types of Business Services (Business Service, Technical Service, Service Offering, Shared Service, Application Service, Billable Service). Business Services of type Business Service are the most abstract and will represent the highest level in your CMDB. These should be how the customer sees the service being delivered, what do THEY call it (forget what IT calls it). Ask your users to describe the services they consume in a day, you'll probably hear "Email", "Purchasing", "Marketing", "Computing", "Telephony", "Finance". A mix of departments and services, that's fine, because your goal is to minimize the time it takes to communicate to your users the state of these services, and to quickly allow your users to communicate to your service desk when there is an issue. I cannot stress enough to talk to your user community to build these, if you build them from an IT point-of-view you'll miss a lot of the value of having a service-aware CMDB. You can read more here: Business service tables
- Service Offering: Derives from a business service, refining the parent business service to a specific business need. These are Services / Capabilities that you wish to track for Availability, SLA Adherence, Outages, etc. They can be made up of CIs and they support Business Services. They consist of a set of Service Commitments that you're going to track. You can then build Availability reports on Service Offerings and show back to the Business. Users can also subscribe to Service Offerings and then put availability gauges on their dashboards. See here: Service offerings
- Technical Service: A dynamic grouping of CIs, based on some common criteria. These are used in Event Management (ITOM) and will roll-up to the buckets you see in that application. You can include Business Services or CIs in these groupings. In general, you'll only use these within the ITOM suite of applications and Event Management specifically. See here: https://docs.servicenow.com/bundle/helsinki-it-operations-management/page/product/event-management/t...
- Shared Service: Similar to Technical Service, a Shared Service is a grouping of Business Services and CIs that are utilized in the IT Financial Management application in order to provide cost transparency. In general, you'll only use these within the ITFM suite of applications. See here: Create IT shared services
- Application Service: Similar to Technical Service, an Application Service is a grouping of CIs and Business Services that are Application specific.
- Billable Service: Similar to Technical Service, a Billable Service is a grouping of CIs and Business Services that you group based on how they are billed.
So, from the above set of artifacts, you'll find you really only want to be concerned with CIs > Service Offerings > Business Services, where your Service Offerings are the Business Services for which you want to track Commitments and then those will roll into customer-facing Business Services.
It's a little confusing, but hopefully the above has helped.
-Rob
