These come from the output of each of the Service Design processes, e.g. security policy provides a security plan.
We use plans as procedures to achieve a particular objective. Put simply, it's a set of intended actions through which we expect to achieve a goal or outcome. When we define plans we include their breadth, time frame and specificity. In some cases, less formal plans such as abstracts are the starting points for Service Design processes. These evolve to become fully pledged plans that are passed to Service Transition.
In ITIL we use different types of plans, but the top down approach is usually at the top of most people's minds. Using the top down approach we can break a system down to gain insight into its compositional sub systems. It's like a 'birds eye view from above'.
In opposite of the top-down approach is of course the bottom-up approach, where we piece together systems to build a grander system. This is much like choosing building blocks to build a house or city. Focus is given to specifying these individual elements which are then linked together to form large subsystems.
See also:- Statement of Requirement (SoR)
- Terms of Reference (ToR)
- Request for Information (RFI)
- Request for Proposal (RFP)
- Request for Quotation (RFQ)
- Invitation to Tender (ITT)
- ISO 9001
- e-TOM
- SOX
- CMMI
- COBIT
- ISO 27001