Halliday & Matthiessen (1999: 417):
In the logico-philosophical orientation, meaning is closely associated with representation, reference, denotation, extension or ‘aboutness’, so the metafunctional scope is restricted to the ideational metafunction: semantics means ideational semantics. … If interpersonal and textual meanings are dealt with by logico-philosophical accounts (they are often outside their scope), they are handled under the heading of pragmatics rather than the heading of semantics. For example, speech act theory was developed as a logico-philosophical interpretation of speech function (or rather its ideational construal) and has come to be included in pragmatics.