Terms that are vital to the performance of obligations are called material terms.

If the parties agree that the performance of obligations under the contract will not be enforceable until a certain condition is fulfilled, that condition is a suspensive one.

They recommend a system under which each tenant is obliged to guarantee performance of obligations by his immediate successor, but not by later assignees (Landlord and Tenant Law: Privity of Contract and Estate (Law Com No 174)).

Principle of legality: data shall be processed in a database belonging to the state information system in the course of performance of public duties, for the purpose of performance of obligations prescribed by an Act, legislation issued on the basis thereof, or an international agreement.

Frustration is a rule which brings contracts to an end in the event of some unforeseen event subsequent to the agreement which would make performance of obligations radically different from that envisaged, for instance because a car for sale is destroyed before it is delivered.