Identify one of the four dimensions of interaction and provide an example/definition

Discussion question:

Essentially, a contract is a vehicle to serve and facilitate the collaboration between parties involved. The contract can be aimed at: (1) meeting the project objectives, and (2) meeting the business objectives and strategic goals of the final customer. A collaborative attitude towards contract management requires careful orchestration of four dimensions of the interaction between buyer and supplier.

Identify one of the four dimensions of interaction and provide an example/definition.

Is anyone more important than the other?