Traced to German Case Law,the theory of collateral obligation comes to develop with the establishment of good faith principle.

The set of self-service deposit in supermarkets is not based on the collateral obligation of contract of sale,but the contract between consumers and supermarkets.

In order to improve the market,law stipulates the party with more imformation the collateral obligation.

Although section 2,article 60 of the Contract Law of our country lays down some provisions,consensus on final decision has not been arrived at in many respects,with the basis of defining collateral duty and the forms of collateral duty still being the focus of disputes.

The article discusses key aspects following breach of collateral duty in the process of performing contract.

And collateral duty is a notable phenomenon therein.

Study on doctrine of liability fixation and legal effects of violating incidental obligation;

The incidental obligation in executing contracts, which is occasionally dealt with in the theory circle, is a traditional issue in the law of debt.

People has begun to realizing the existence of the contractual incidental obligation.

The subsidiary obligation as a legal term has not been defined in the civil legislation of various countries, but it is now attracting increasing attention in the field of contract laws.