请修缮这段文字要求表达要清晰语法要准确。One of Searles major contributions to the theory of speech act is the indirect speech act theory It is a direct speech act that a person realizes his communicative intention direct

Searle's "indirect speech act theory" is a significant contribution to the theory of speech acts. A direct speech act involves a person achieving their communicative intention through the literal meaning of the discourse form. On the other hand, an indirect speech act involves achieving effects beyond the discourse itself through the discourse form. Searle emphasizes that the problem to be addressed by the theory of indirect speech act is how the speaker expresses indirect "illocutionary force" through "literal intention".

Searle categorizes speech acts into five classes, each of which has a common and universal purpose. The first class is representative speech act, which refers to the speaker's words conforming to objective facts, and the speaker having a degree of assurance about the content of their statements. Examples of representative speech acts include stating, claiming, denying, and informing.

The second class is directive speech act, which involves the speaker attempting to prompt the hearer to do something to varying degrees. The topic of discourse aims to encourage the hearer to take action. Examples of directive speech acts include begging, demanding, advising, commanding, and inviting.

The third class is commissive speech act, which refers to behaviors that the speaker promises to undertake in the future. Examples of commissive speech acts include committing, promising, guaranteeing, and refusing.

The fourth class is expressive speech act, which refers to the speaker's emotional attitude towards something. Examples of expressive speech acts include apologizing, thanking, welcoming, and congratulating.

The fifth and final class is declarations speech act, which primarily refers to the speaker's ability to change the conditions or circumstances of relevant things through such acts. Examples of declarations speech acts include declaring, nominating, appointing, and naming