Semantic Interpretation Based on the Multi-World Model

This paper proposes the Multi-World Model as a new logical framework for semantic interpretation of natural language. The model represents worlds as first-order axiomatic systems linked through interpretations between worlds, which are mappings of theorems between these ax-iomatic systems. Results of semantic interpretation are assumed to be constructed on such a multi-world structure. To understand ambiguous sentences, people make assumptions to complement information that is unknown to them. If an assumption is consistent with information that is known to them, then they will support that assumption and make a unique interpretation of the sentence. When a new sentence comes in whose interpretation conflicts with a previous interpretation , they will consider another assumption. When the context is fixed, the whole interpretation will be decided by selecting the most, preferable assumptions. The Multi-World Model was designed as a formal description of facts, assumptions, background knowledge, and their relationships. This paper defines the Multi-World Model and presents its application to semantic interpretation with concrete examples. 1 Introduction People use background knowledge to interpret sentences, to resolve anaphora, and to check the coherence of a text. If their background knowledge is not sufficient for this purpose, then they make assumptions in order to understand their meaning. Generally, people interpret sentences by making assumptions based on partial information. The assumptions may be inconsistent with each other, and therefore the factual information derived from the sentences is related to each of the assumptions separately. It is difficult to represent the meaning of sentences by logical expressions when assumptions must be taken into account. Reiter\s default logic [Reiter, 1980] is one way to overcome this problem. The model-theoretical basis of the Multi-World Model is a Kripke Model [Landman, 1986], and default reasoning can be expressed by using the modality of possibility. Another problem is that semantic interpretation changes according to the growth of information obtained from the sentences read. The Multi-World Model can treat dynamic interpretation by using assumptions and knowledge represented by logical formulae. The main ideas in this paper are as follows: 1. When a sentence is processed, a fact or assumptions are derived from it. 2. Abductive worlds are constituted of individual assumptions , and the confronted world is constituted of facts. 3. These worlds are considered as first-order axiomatic systems. 4. A relationship between a fact and an assumption is defined as a mapping from a confronted world to an abductive world. …