tailieunhanh - Báo cáo khoa học: "INFORMATION STATES AS FIRST CLASS CITIZENS"

The information state of an agent is changed when a text (in natural language) is processed. The meaning of a text can be taken to be this information state change potential. The inference of a consequence make explicit something already implicit in the premises - - . that no information state change occurs if the (assumed) consequence text is processed after the (given) premise texts have been processed. Elementary logic (. first-order logic) can be used as a logical representation language for texts, but the notion of a information state (a set of possibilities - - namely first-order models). | INFORMATION STATES AS FIRST CLASS CITIZENS j0rgen Villadsen Centre for Language Technology University of Copenhagen Njalsgade 80 DK-2300 Copenhagen s Denmark Internet jv@ ABSTRACT The information state of an agent is changed when a text in natural language is processed. The meaning of a text can be taken to be this information state change potential. The inference of a consequence make explicit something already implicit in the premises . that no information state change occurs if the assumed consequence text is processed after the given premise texts have been processed. Elementary logic . first-order logic can be used as a logical representation language for texts but the notion of a information state a set of possibilities namely first-order models is not available from the object language belongs to the meta language . This means that texts with other texts as parts . propositional attitudes with embedded sentences cannot be treated directly. Traditional intensional logics . modal logic allow via modal operators access to the information states from the object language but the access is limited and interference with extensional notions like standard identity variables etc. is introduced. This does not mean that the ideas present in intensional logics will not work possibly improved by adding a notion of partiality but rather that often a formalisation in the simple type theory with sorts for entities and indices making information states first class citizens like individuals is more comprehensible flexible and logically well-behaved. INTRODUCTION Classical first-order logic hereafter called elementary logic is often used as logical representation language. For instance elementary logic has proven very useful when formalising mathematical structures like in axiomatic set theory number theory etc. Also in natural language processing NLP systems toy examples are easily formalised in elementary logic Every man lies. John is a man. So John lies.