To be able to discuss IT service and potential scope, ambition and effect of IT services we need to establish a few terms. I will use three different terms that is very related to each other.
Service Portfolio: The content of a Service Portfolio describes what capabilities and business processes that a customer have, value and prioritize as of today and the future. This is the basis (customer requirements) that IT need to support and develop with matching IT services. The IT services is completely driven by customer needs. The Service Portfolio can be documented in any already existing or arbitrary format.
Service Catalog: The content of a Service Catalog describes all the IT services that is available for the customer at the moment. Any IT service description clearly states the service content, commitment, limitations etc. The content must reflect the available IT services for a customer and is favorable described as a sales brochure in either electronic- or paper- form.
Request Catalog: The content of a Request Catalog describes all the ways a user can interact with available IT services. It is how a user requests ability to consume an IT service. To add, change, move or delete ability to consume it. The content is completely an effect of IT's ability to bundle requests. The Request Catalog is usually available for users as a web based request portal.
Now when we have three terms defined on a basic level we can continue with a few examples that is categorized on focus, based on these terms. A desirable effect is related to what part is in focus and the basic conditions to achieve them. This is just a few examples to show how one can categorize desirable effects to enable a strategy and plan that is not to fragmented.
Depending on ambition, and effects you pursue, you can use this way of sorting to scope and focus your initiative to increase probability of a good outcome. Do not try to do more than you can handle. There is a very important relation between the three different terms. A Request Catalog get higher quality if the content is a result of a working Service Catalog where the requests are defined based on how a user is supposed to interact with the available IT services. A Service Catalog in its turn get higher quality if the content is a result of a working Service Portfolio where the Service Catalog content is based on business outcomes prioritized by the customer as important and the IT services necessary to manage the business. The Service Portfolio verifies that the development of the IT services is based completely by the customers needs and future challenges.