When I last looked in this area I became tempted to avoid the data model viewpoint - healths view was too focused on care plans as documents.
I think the main day 2 day practitioners (nurses and social workers) actually view this from a workflow perspective Nursing process - Wikipedia
Documents are produced during this process but the workflow and communication was quite important. I believe 10-15 years ago NHS Digital also looked at tackling it this way. They had something like this (from Welcome to the Physical Activity IG - Physical Activity Implementation Guide v1.0.1 - I do like how this guide was laid out)
@iain + INTEROPen did discuss this IHE guide around care planning https://ihe.net/uploadedFiles/Documents/PCC/IHE_PCC_Suppl_DCP.pdf several years ago.
