The initial focus of the reference set development work is to establish a clear set of initial requirements, which may require further elaboration at a later date. The requirements should include an assessment of the release requirements for the reference set from a user perspective. 

Defining the scope of the reference set involves answering a range of different questions related to each step of the development process. Following questions are relevant to consider when defining the scope of a reference set. Additional questions will probably be relevant for a specific development process.

• What is the main purpose of the reference set?
• Who are the users of the reference set?
• What is the scope of content of the reference set?
• Who is responsible for developing and maintaining the reference set?
• Should we develop a new reference set or does any existing reference set meet our requirements?

Once the scope of the reference set and the requirements has been identified, it is essential that an owner of the reference set is clearly identified (this may be an individual or a specific group). Furthermore, the requirements must be clearly documented, particularly the scope, purpose and use case(-s). 
The owners of the reference set must then assess what content to be included in the reference set. This process may involve evaluating existing reference sets, or assessing what parts within the International Release of SNOMED CT (and potentially National and Affiliate Editions) will meet the stated requirements. At this stage the requirements for ensuring the content of the subset is quality assured should also be documented.