No specific guidance beyond the provisions contained in Section 2 of the Planning and Compulsory Purchase Act 2004 and Regulation 4 of the Town and Country Planning (Regional Planning) (England) Regulations 2004 has been issued on either of the points contained in (a) or (b) of the question. However the provisions of the Act and regulations are briefly explained in paragraphs 2.2 and 2.3 of Planning Policy Statement 11: Regional Planning Strategies.