17.7.1 Meaning as Action

An approach that holds considerable appeal when we consider the semantics of imperative sentences is the notion of meaning as action. Under this view, utterances are viewed as actions, and the meanings of these utterances reside in procedures that are activated in the hearer as a result of hearing the utterance. This approach was followed in the creation of the historically important SHRDLU system, and is summed up well by its creator Terry Winograd (1972).

One of the basic viewpoints underlying the model is that all language use can be thought of as a way of activating procedures within the hearer. We can think of an utterance as a program—one that indirectly causes a set of operations to be carried out within the hearer's cognitive system.

A more recent procedural model of semantics is the executing schema or x-schema model of Bailey et al. (1997), Narayanan (1997a, 1997b), and Chang et al. (1998). The intuition of this model is that various parts of the semantics of events, including the aspectual factors discussed on page 32, are based on schematized descriptions of sensory-motor processes like inception, iteration, enabling, completion, force, and effort. The model represents the aspectual semantics of events via a kind of probabilistic automaton called a Petri net (Murata, 1989). The nets used in the model have states like ready, process, finish, suspend, and result.

The meaning representation of an example like Jack is walking to the store activates the process state of the walking event. An accomplishment event like

Jack walked to the store activates the result state. An iterative activity like Jack walked to the store every week is simulated in the model by an iterative activation of the process and result nodes. This idea of using sensory-motor primitives as a foundation for semantic description is also based on the work of Regier (1996) on the role of visual primitives in a computational model of learning the semantics of spatial prepositions.