Parol evidence是合同以外的证据，Parol evidence rule reasoning不包括合同以外的任何证据。在Parol证据规则的应用中，通常理解两个组成部分，即整合规则和解释规则。在整合规则中，书面协议是各方共同努力的唯一协议。这一组成部分确保法院不允许任何可能改变合同内容和最初意图的合同以外的证据。法院在适用帕洛尔规则的这一组成部分时，确保合同的原始完整性得到维护。
Parol evidence is evidence outside the contract and the Parol evidence rule reasoning is not to include any evidence that is outside the contract. In application of the Parol evidence rule, two components are understood usually which are the integration rule and the interpretation rule. In the integration rule, the written agreement is the only agreement upon which the parties work on. This component ensures that the court does not allow for any evidence outside the contract which could potentially change the contents and the original intention of the contract. The court on applying this component of the Parol rule ensures that the original integrity of the contract is maintained.
According to the Parol evidence rule, the extrinsic terms that are outside the originally written contract will be excluded as evidence for the party only where the document of the contract is wholly agreed upon as a written contract. There is no application of Parol evidence rule in the case of a contract that is partially written and partly oral. The contractual form hence becomes necessary for Parol evidence rule to apply.
In the interpretation aspect, the court will look at the terms of the contract and interpret the meaning when applying the Parol evidence rule. The interpretation aspect is one reason that the Parol evidence rule and exceptions cannot be stated as a hard and fast rule. They must be applied based on context and it is necessary for the court to identify the meaning of terms and interpret them accordingly. Where court ascertains that the meaning of the terms are fixed and are presented properly, then the Court will apply the Parol evidence rule. The significance of the Parol evidence rule in protecting the integrity of contracts is further enhanced when the Court in the interpretation process processes the situation in a factual matrix. The Court when processing the details of the contract and the validity of the terms would place itself in the same factual matrix that would have been used when the contract was created in the first place. The evidence in the surrounding circumstances that went into the creation of the contract are considered.