The Ideational And Interpersonal Aspects Of A Register

Halliday & Matthiessen (1999: 378):

A particular domain model within the ideation base correlates with a particular exchange relationship within the interaction base and together they form the ideational and interpersonal aspects of a register. 

An exchange relationship thus has ideational implications: it involves the exchange of some ideational meanings rather than others and it embodies a division of labour between the interactants in the exchange relationship. 

For example, in a service encounter in a local shop (cf. Halliday & Hasan, 1985; Ventola, 1987), the customer may demand goods and information about goods within the relevant domain and the server supplies these on demand and demands goods (payment) in return; and this involves the general domain of business transaction and the particular domain of the business (e.g. hardware). 

An exchange relationship thus gives interpersonal values to meanings within the domain model it is associated with. 

For example, as we have seen, the ideation base embodies both congruent and metaphorical construals of experience; and these variants will be selected partly according to differences in interpersonal distance along dimensions such as age and expertise.

Interpersonal Semantics: Exchange Relationship

Halliday & Matthiessen (1999: 377-8):

Midway between potential and instance, sets of such strategies cluster within ranges of tenor values. Such a cluster is the interpersonal analogue of a domain in the ideation base: it is a region within the overall interpersonal space of meaning, selected according to tenor, just as a domain is a region within the overall ideational space of meaning, selected according to field. 

The options in interpersonal meaning that make up the cluster together enact a tenor relationship, 

such as that between a client and a server (unequal in power, low in familiarity, neutral in affect) where the client initiates demands for goods-&-services and information about them and the server responds, 

such as that between two friends (equal in power, high in familiarity, positive in affect) where the interpersonal options are wide-ranging, or 

such as that between the writer of a weather report and the readers (unequal in expertise, no familiarity, neutral in affect) where the writer gives information and the readers accept. 

We might call such a cluster an exchange relationship to foreground that it is semantic (i.e. constituted in meaning through exchanges of meaning) and that it is interpersonal (rather than one-sidedly personal). 

To indicate that it is analogous to a domain model, we might have called it an exchange or interaction "model"; but we have avoided that term because it suggests a construal of something and construal is the ideational mode of meaning — it is more like a protocol than like a model.

The Semantic System Or "Meaning Base"

 Halliday & Matthiessen (1999: 376, 377):

The semantic system, or "meaning base", thus consists of the three familiar metafunctional contributions: the ideation base, the part of the meaning base that we have focussed on, but also the other two bases, the interaction base and the text base. All three bases are extended along the cline of instantiation from potential to instance. … Table 9(1) summarises those aspects of the three bases to be discussed.

Exchange Relationships And Domain Models

Halliday & Matthiessen (1999: 378): 

A particular domain model within the ideation base correlates with a particular exchange relationship within the interaction base and together they form the ideational and interpersonal aspects of a register. An exchange relationship thus has ideational implications: it involves the exchange of some ideational meanings rather than others and it embodies a division of labour between the interactants in an exchange relationship. … An exchange relationship thus gives interpersonal values to meanings within the domain model it is associated with.

The Interaction Base: Exchange Relationship Protocols

Halliday & Matthiessen (1999: 377-8): 

Midway between potential and instance, sets of such strategies cluster within ranges of tenor values. Such a cluster is the interpersonal analogue of a domain in the ideation base: it is a region within the overall interpersonal space of meaning, selected according to tenor, just as a domain is a region within the overall ideational space of meaning, selected according to field. The options in interpersonal meaning that make up the cluster together enact a tenor relationship … We might call such a cluster an exchange relationship to foreground that it is semantic (i.e. constituted in meaning through exchanges of meaning) and that it is interpersonal (rather than one-sidedly personal). To indicate that it is analogous to a domain model, we might have called it an exchange or interaction “model”; but we have avoided that term because it suggests a construal of something and construal is the ideational mode of meaning — it is more like a protocol than a model.