Locutionary acts
Like Austin, but unlike Searle, Bach and Harnish argue for the concept of locutionary acts: acts of using sentences with “a more or less definite ‘sense’ and a more or less definite ‘reference,’” in Austin's words. They are more explicit than Austin, and argue that determining what someone has (locutionarily) said by uttering a sentence amounts to determining
the operative meaning of the sentence uttered
the referents for the referring expressions
the properties and relations being ascribed
the times specified
With this information the hearer identifies what a speaker has said, at the locutionary level. From a contemporary perspective, the most remarkable point here is, in our opinion, that they see the determination of the locutionary act by the hearer, not as a matter of merely decoding the conventional meaning of the sentence uttered, but as a matter of inference that has to be based on linguistic meaning plus contextual information concerning the speaker's intentions. Grice did not claim that what a speaker said was determinable without consideration of the speaker's intentions; quite the contrary. But he was not particularly explicit about the way it was done, and the received view, anyway, has been that inference was exclusive to the ‘calculation’ of implicatures.
The distinction between locutionary and illocutionary acts of saying also offers Bach and Harnish a useful conceptual tool for treating potentially problematic cases of discordance between utterance content and speaker's intentions, such as slips of the tongue, false referential beliefs, and irony.
To go from the locutionary to the illocutionary content, if there is any, the hearer has to infer the communicative intention of the speaker, and to do that, the hearer needs more information. Among other things, the hearer will have to make use of the Communicative Presumption (CP) that they state as follows:
The mutual belief in the linguistic community CL to the effect that whenever a member S says something in L to another member H, he is doing so with some recognizable illocutionary intent. (Bach and Harnish 1979, 61.)