In the framework of the case law, a distinction was made between two types of contractual obligations: "obligation of outcome" (absolute obligation) and "obligation of diligence". In the case of positive results, the object of the promise is the achievement of a certain and defined result, and failure to achieve it constitutes in itself a breach of the contract (subject to the laws of frustration). On the other hand, the obligation to make an effort is essentially a behavioral obligation, in which the party undertakes to take the appropriate measures, skill, diligence, and due diligence in order to achieve the goal, without committing to achieving it in practice. In the case of the obligation to make an effort, the existence of a gap between the desired result and the result obtained does not in itself constitute a breach, and the debtor will be liable only if the failure to achieve the result is related to his negligence, lack of skill or unreasonableness in his actions (see - Other Municipality Applications 10745/06 Keren Azoulay et al. v. ORT Academic College, Appeal of Shona Singalovsky - Pollak, Tel Aviv, at paragraph 14, to the judgment of the Honorable Justice Arbel (July 13, 2009); Daniel Friedman and Nili Cohen, Contracts (2003) Volume 3 388-390 - which were adopted, inter alia, other Municipality Applications 3313/13 David Nagar v. Rosh Ha'Ayin Municipality (November 22, 2015)). With regard to proving a breach of the duty of diligence, the Honorable President Justice Beinisch held the following in Other Municipality Applications 444/94 Orot Representation of Artists v. Atari, IsrSC 51(5) 241, 254:
"The question of proof regarding the non-existence of diligence obligations is a complex question due to the nature of these obligations. It seems that the plaintiff will rarely find direct evidence of the defendant's failure to fulfill his obligations. This will be the case, for example, when the defendant expressly declares that he does not intend to fulfill his obligations. This is also the case when the defendant took external steps and behaved in a manner that shows that he does not intend to fulfill his obligations. Another possible way that the plaintiff may be able to prove a breach of an obligation is to prove the defendant's negligence by bringing evidence of proper and acceptable conduct for the performance of such an obligation, from which the defendant deviated. However, even this method is not necessarily suitable for all cases in which we are dealing with the obligation of effort.