ISO 24617-2 is an international standard established by the International Organisation for Standardisation ISO in 2012. The ISO 24617-2 annotation scheme was developed by a group of 10 researchers, consisting of Harry Bunt (Tilburg, project leader), Jan Alexandersson (Saarbrücken), Jean Carletta (Edinburgh), Jae-Woong Choe (Seoul), Alex Chengyu Fang (Hong Kong), Koiti Hasida (Tokio), Volha Petukhova (Tilburg; Saarbrucken), Andrei Popescu-Belis (Martigny), Claudia Soria (Pisa), and David Traum (Marina del Rey; Playa Vista).
The ISO 24617-2 scheme supports the marking up of spoken, written and multimodal dialogue with information about dialogue acts. A dialogue act has been defined as:
“Communicative activity of a dialogue participant, interpreted as having a certain communicative function and semantic content” (ISO 24617-2).
The notion of a dialogue act, which was first introduced in Bunt (1979), may be viewed as a computational and empirically-based variant of the classical speech act concept as introduced by Austin, Searle, and other language philosophers.
Dialogue acts are units in a dialogue that correspond to changes that the speaker intends to bring about in an addressee’s information as a result of the addressee understanding the speaker . A dialogue act has two main components: a communicative function and a semantic content. The communicative function species how the semantic content changes the information state of an addressee who understands the speaker’s communicative behaviour. Further components of a dialogue act are qualifiers for sentiment (such as happy, angry, surprised,…), certainty and conditionality; and dependence relations (such as question-answer), which are indispensable for determining the semantic content of a responsive dialogue act. Additionally, rhetorical relations between dialogue acts may be marked, indicating e.g. that one dialogue act motivates the performance of another one. ISO 24617-2 dialogue act annotation includes the marking up of the sender (or ‘speaker’) and the addressee(s) of the dialogue act, possible additional participants (such as an audience), the segment of discourse that expresses the dialogue act (the ‘functional segment’), the communicative function, the dimension (or type of semantic content), qualifiers, dependence relations, and rhetorical relations. The official ISO definitions of the standard’s communicative functions, dimensions, qualifiers, and dependence relations, in the form of ISO ‘data categories’, are documented in the unpublished paper Data categories for dialogue acts (Bunt, 2012).
The standard does not specify the rhetorical relations that may be used, but it is recommended to use the recently proposed standard ISO 24617-8 for this purpose, or at least a set of relations that is compatible with the list of ‘core’ relations defined in this new standard – see Bunt & Prasad (2016) for this list.