A fairly traditional document hierarchy, in line with ISO 9001 and other standards looks like this:
This process tends to support best an approach where there is a policy that states requirements to do X, a procedure that gives the who, what, when of X, and work instructions that provide the how of X, which results in a lot of records providing X was done.
But life is complicated, and there are sets of activities that combine the Xs in a wide variety, and in complicated environments there may be multiple ways to bundle the Xs.
This is why I add a layer between policy and procedure, called the program, which is a mapping requirement that shows the various ways to interpret the requirements to specific needs.
The program document level shouldn’t be a stranger to those in the GMP world, ICH Q11 control strategy and the Annex 1 (draft) contamination control strategy are two good examples. What this document does is tie together processes and demonstrates the design that went into it.
The beauty of this document is that it helps translate down from the requirements (internal and external) to the process and procedures (including technology), how they interact, and how they are supported by technical assessments, risk management, and other control activities. Think of it as the design document and the connective tissue.