1.the promisor and promisee are named in the document or so described as to be capable of identification when it is delivered.
文件中列明了诺言人和受诺人，或者对二者做出描述并在交付时能够确认。
2.It may be given by the promisee or by some other person.
可以由受诺人提供，也可以由他人提供。
3.if the promisee conferred the benefit as a gift or for other reasons the promisor has not been unjustly enriched;
or受诺人将利益赠与的，或者由于其他原因诺言人没有不当得利的；
4.reinstatement of the requirement of the condition is not unjust because of a material change of position by the promisee or beneficiary;
and不会因为受诺人或者受益人地位的实质性改变使得条件的恢复导致不公；
5.When a Person May Be Both Promisor and Promisee
当一个人既是允诺人又是受允诺人