Common open space. Land within the CCRC parcel or lot which is not specifically reserved for the support of the CCRC facilities and which is not covered by buildings, roads, driveways, parking areas, or service areas which is not set aside as private yards, patios or gardens for residents shall be common open space. Further, all common open space shall be open and unobstructed to the sky; flagpoles, sculptures, benches, swimming pools, tennis courts, atriums, trees and similar objects shall not be considered obstructions. The area of common open space shall equal at least 50% of the total area of the CCRC parcel or lot, and no more than 25% of the minimum required common open space shall be situated within wetlands. The common open space shall have a shape, dimension, character and location suitable to enable its enjoyment and use for conservation, recreation and agriculture purposes by the residents of the CCRC. Further a permanent conservation restriction of the type described in MGL c. 184, § 31 (including future amendments thereto and corresponding provisions in future laws), running to or enforceable by the Town, shall be recorded with respect to the common open space. Such restrictions shall provide that the common open space shall be retained in perpetuity for one or more of the following uses: conservation, recreation or agriculture. Such restriction shall be in a form and substance as the Planning Board shall prescribe, including the management of said conservation restriction by the Town Conservation Commission, Trustees of Reservations, Essex County Greenbelt Association or other agency or body, all as subject to the approval of the Planning Board.