In one aspect, a computer-implemented method of performing multi-user design negotiation on a computer-aided design (CAD) software is disclosed. The method includes: receiving, from a first user, a design change to the geometric shape design, and obtaining information of the design change implementable on a CAD model of the geometric shape design through the CAD software; storing the information of the design change as a design change suggestion (DCS) object; transmitting the DCS object, together with the CAD model, to a second user; and receiving, from the second user, an instruction to the DCS object, and performing an operation corresponding to the instruction to the DCS object. In response to a what-if instruction, the operation is a what-if operation to the geometric shape design with the design change according to the DCS object. In response to an accepting or rejection instruction, the operation includes accepting or rejecting the design change.
