Abstract: A locking protocol and the corresponding locking request scheduling algorithm is proposed for concurrency control in two-dimensional workspaces.It can be applied to any cooperative work in a planar area,such as cooperative drawing.The protocol is based on pessimistic lock,free of deadlock.The locking granularity is a planar area with an arbitrary shape or size,instead of a specific data structure. The effectiveness of the proposed locking protocol and the algorithm in practical use was well proved in a distributed,real-time,cooperative drawing system.This implementation of the locking protocol is based on multi-agent system model,which utilizes the concept of emotional value of an agent to determine when should free a lock,supporting initiative cooperation as well as fine-granularity perception among concurrent operators.