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<?xml version="1.0" standalone="yes"?> <Paper uid="C92-4193"> <Title>ON THE ACQUISITION OF CONCEPTUAL DEFINITIONS VIA TEXTUAL MODELLING OF MEANING PARAPHRASES</Title> <Section position="3" start_page="0" end_page="0" type="metho"> <SectionTitle> 2 TEXTUAL MODELLING OF MEANING PARAPHRASES 2.1 APPROACH </SectionTitle> <Paragraph position="0"> The KONTEXT model \[Haenelt/KOnyves-T6th 91 \] assumes that natural language texts do not communicate complex concepts immediately and at once, but rather provide sequential instructions concerning how to construct them incrementally. The instructions are established by the natural language expressions, which, used in texts, not onty have the function of denoting concepts, but rather can be seen as operators which contribute to the construction of thematic structures and reference objects. Thematic structure and reference objects then guide the access to eon~ eepts and the incremental construction of new concept definitions communicated by the text. The KeN-TEXT model structures the information conveyed in a text and the information describing its contextual organization into five layers of text representation: sentence structure, thematic structure, view (on background knowledge), and background knowledge.</Paragraph> <Paragraph position="1"> In order to construct a conceptual definition in accordance with a meaning paraphrase, the paraphrase must be analyzed step by step under textual aspects.</Paragraph> <Paragraph position="2"> Each natural language expression contributes information towards the construction of at least one of the four upper layers of text representation. The iuformation of rite expressions of the meaning paraphrase is analyzed and a five-layereA multi-state text representation is generated. 'ltfis generation includes operations which incrementally construct (new) concept(s) and establish the relationship between natural language expressions, reference objects ,and concepts via the thematic structure.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.2 EXAMPLE </SectionTitle> <Paragraph position="0"> As an example the fi~llowing meaning paraphrase of &quot;blank&quot; is used: &quot;A blank piece of paper has no writing or other mark.~ on it.&quot; \[COBUILD 87\]. A textuM representation of this paraphrase is shown in figure 1. The figure illustrates how the conceptual definition of &quot;blank&quot; is constructed step by step. It shows a text representation with Iigur layers and five states.</Paragraph> <Paragraph position="1"> The 'sentence structure' contains the lexemes, their dependency structure (and further syntactic features not shown here). The information of the 'sentence structure' basically lollows the PLAIN-grammar \[Hellwig 80, 88\]. The 'thematic structure' traces the discourse development. It shows contexts (cL boxes 1-5 in figure 1; the numbers refer to file discourse states of their creation), and reti~rences to contexts (represented by the lines between the boxes) which correspond to discourse state transitions. The 'reference structure&quot; contains the reference objects, their</Paragraph> </Section> </Section> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> AC'YES DE COLING-92, NANq'ES, 23-28 ^OF;f 1992 l 2 1 0 PREC. OF COLING-92, NANfES, AU(L 23-28, 1992 </SectionTitle> <Paragraph position="0"> development and relationship. The layer of 'view' shows views on the 'background knowledge' which have been established by state transitions. The 'background knowledge' (which is shown in figures 2 and 3) contains conceptual descriptions of prototypical situations in accordance with the model of Semantic Emphasis \[Kunze 91\]. These descriptions are explained in more detail in section 2.3.1.</Paragraph> <Paragraph position="1"> The states trace the incremental construction of the filial view (\[5\]) of the meaning paraphrase and the (re-)definition of the relationship between natural language expressions and reference objects. So, whilst the dellniendnm &quot;blank&quot; had no conceptual definition in the initial state (1), in the final state (5) a conceptual definition has been constructed by analyzing the meaning paraphrase under textual aspects.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 2.3 THE KONTEXT DICTIONARY </SectionTitle> <Paragraph position="0"> The contribution natural language expressions make towards the layers of the text representation is described as a lexicalized text grammar. The informao tion of all the five layers is modelled in feature structures which are processed with the CFS-system \[K6nyves-T6th 91\] \[B6ttcher 91\]. Due to the formalism chosen the basic operation is unification.</Paragraph> <Paragraph position="1"> The conceptual modelling of the KONTEXT dictionary is based on the model of Semantic Emphasis \[Kunze 91\]. The core components of this model are 'basic semantic forms' which describe prototypical situations commonly referred to by tile verbs of a verb field. A 'basic semantic form' is a proposition consisting of predicates and (propositional or elementary) arguments. So, e.g. the propositional description ofa 'write'-situation is: CAUSE ( ACT (x), El&quot; (BEC (EXIST(w,t)), BEC (PLACE-ON (q,w)))). This description can be paraphrased in the tollowing way: An action of 'x' causes a 't' to become to exist as 'w' and this 'w' to become placed somewhere such that a relation 'ON' holds true between 'q' and 'w'. The scheme of 'write' is based on the general scheme of a produce-situation. null Situation descriptions provide the basic schemes of the layer of background knowledge of dictionary entries. They are used for the construction of the layer of 'view' during text analysis. They can immediately be applied to the modelling of verbs. For modelling further word classes the following extensions are made: Similarly to Conceptual Dependency approaches (e.g. \]Schank 75\]) in file KONTEXT approach 'basic semantic forms' are the backbone of conceptual modelling. Verbs and deverbative abstract nouns are modelled as referring to prototypical situations following the descriptions of the model of Semantic Emphasis. Prepositions are modelled as denoting parts of those situations which have actants which in the surface form can be realized with the preposition in question. Noons are modelled as denoting participants of situations, and adjectives as denoting situations focusing on a particular participant. The defining situations of nouns and adjectives are determined in accordance with the meaning paraphrases of \[COBUILD 87\] following the textual conditions of applying the situations concerned. CO-BUILD definitions are also used in order to describe field external distinctions of verbs.</Paragraph> <Paragraph position="2"> The formal components of the conceptual representation are the feature structure representation of 'basic semantic forms', instantiation rules and role derivation rules following tile approach of \[Kunze 911.</Paragraph> <Paragraph position="3"> The propositional description of the 'write'-situation is modelled in feature structures in tile following way: Predicate names are written in capital letters. @<> indicates reference to a type, where <> enclose path descriptions. The arguments of predicates are values of the feature 'prop'. Elementary arguments correspond to possible reference objects.</Paragraph> <Paragraph position="4"> Depending on the predicates used, instantiation rules are applied in order to get a more refined description of the situation. E.g. a proposition BEC(A) instantiates a monotonic path such that initially NOT(A) holds true, mad finally (A) holds true.</Paragraph> <Paragraph position="5"> NOT(A) is also called the 'presupposition' of the situation, and (A) is (one of) its 'assertion(s)' \[Jung/ Kilstner 90\]. The predicate ET has two propositional arguments and requires its arguments to be instantiated at the same time. Thus, either the presupposition or the assertion of both arguments is selected. For elementary argnments case relations are derived in accordance with a purely formal definition scheme (Kunze's approach (91) provides a theoretical description and formalization of Fillmore's (68) deep cases).The resulting case relations of e.g. the ACT~ DE COLING-92, NArerES, 23-28 AOt)r 1992 I 2 l l Pane. OF COLING-92, NANTEs, AUG. 23-28. 1992 'write'-situation are: 'agens of ACT', 'to-object of EXIST', 'goal of PLACE-ON', 'goal of EXIST', and 'to-object of PLACE-ON'.</Paragraph> <Paragraph position="6"> A perspective on the situation is determined by emphasis and the selection of actual case relations from the derived potential roles. By means of emphasis \[Kunze 911 certain partial propositions are moved into the foreground.</Paragraph> </Section> </Section> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> 2.3.2 TEXT STRUCTURE INFORMATION </SectionTitle> <Paragraph position="0"> Based on the model of Semantic Emphasis information concerning the reference structure and the thematic structure can be derived systematically from conceptual information.</Paragraph> <Paragraph position="1"> Potential reference objects are provided for all possible participants of the situation. The roles they play in the situation are expressed as case relations.</Paragraph> <Paragraph position="2"> Thematic information includes information such as which participants can be realized emphatically (not emphatically) in which surface form. So, e.g. file primary effect of the action of writing (in the prototypical case) is that a writing exists, while it is less important where it appears. Therefore at least one of the arguments of the EXIST-predicate has to be realized emphatically (i.e. not by a prepositional phrase) and those of the PLACE-ON-predicate are either realized without emphasis (by a prepositional phrase) or they are not realized at all. This information then provides the basis for mechanisms of referring to contexts. E.g.</Paragraph> <Paragraph position="3"> only those reference objects which have been realized emphatically can later be referred to by an anaphorical pronoun.</Paragraph> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 2.4 APPLICATION OF THE KONTEXT DIC- TIONARY TO MODELLING THE MEA- NING PARAPHRASE </SectionTitle> <Paragraph position="0"> The words of the meaning paraphrase (&quot;A blank piece of paper has no writing on it&quot;) contribute to the constitution of the text representation in the following way: &quot;Has&quot; does not make a contribution to the conceptual definition. It only &quot;provides a verb for the structure&quot; \[COBUILD 87:6671 and indicates the abstractum &quot;writing&quot;.</Paragraph> <Paragraph position="1"> &quot;Blankpiece ofpaper&quot; introduces a participant of a situation. Its surface form and its syntactic function contribute to determining which participant of which situation it can be. The defining situation of &quot;paper&quot; (cf. meaning paraphrase of &quot;paper&quot;) must be compatible with the newly composed situation it becomes a participant of (e.g. the situation of this meaning paraphrase). Otherwise a further text is requirod in order to solve this conflict.</Paragraph> <Paragraph position="2"> &quot;Writing&quot; as a noun denotes a participant of a simarion, and as a deverbative abstractum at the same time introduces the situation of which it is a participant. This is the 'write'-situation described in section 2.3.1.</Paragraph> <Paragraph position="3"> &quot;No&quot; does not make a conceptual contribution of its own. It, however, has the effect that tile presupposition of the 'write'-situation must be selected. &quot;On&quot; as a preposition denotes parts of those situations which have aclants which in the surface form can be realized with this preposition. In this case it is a complement of &quot;writing&quot; and serves to introduce the actant of &quot;writing&quot; which is determined by the first argument of PLACE-ON. As a preposition it introduces a non-emphatic realization of the actant.</Paragraph> <Paragraph position="4"> &quot;It&quot; as a complement of &quot;on&quot; is identified as the 'goal of PLACE-ON' of the 'write'-situation. As a pronoun it refers to an antecedent which had been realized emphatically. In this case this is the subject of the sentence. Thus, a reference identity of anaphora and antecedent is constructed, and then both expressions refer to the reference object which denotes the 'goal of PLACE-ON' of the ' write'-situation.</Paragraph> <Paragraph position="5"> In terms of feature structures the result can be expressed in the following way: view: \[t: l\] 5: \[ inst: \[ sit-l: I name: negation al: \[name: exist-as al: ref: =<view 5 roles goal exist ref> a2: ref: =<view 5 roles to-obj exist ref> \]\] sit-2: \[ name: negation at: \]name: placed-on al: ref: =<view 5 roles goal place-on ref> a2: ref: =<view 5 role&quot;s to-obj place-on ref>111 role.s: \[ goal: \[ exist: \[ ref: =<refer 2> emph: plus \] AC'~rES DE COLING-92, NAICrES, 23-28 AO~I 1992 1 2 l 2 Pate. OF COLING-92, NANTES, AU~3.23-28, 1992 place-ml: \[ ref: =<refer 1> emph: minus \]\] to-obj: \[ exist:\[ ref: \[ \] emph: plus \] place-on: \[ ref: \[ \] emph: minus \]\]\]\] background: prop: write@<prop> \] Figure3: Feature structure representation of the result The value of the feature 'inst' denotes the part of the situation description that corresponds to &quot;no writing on it&quot;. It has been derived by applying instantiation rules to the propositional part of the conceptual description and by selecting the presupposition. Relationships to other layers of text representation are denoted as patti specifications (<>).</Paragraph> </Section> <Section position="7" start_page="0" end_page="0" type="metho"> <SectionTitle> 3 EXPLANATION OF THE RESULTING CONCEPTUAL DEFINITION </SectionTitle> <Paragraph position="0"> The value of the feature 'inst' can be regarded as the conceptual definition of &quot;blank&quot;. The meaning paraphrase, however, does not really explain &quot;blank&quot;. It rather explains what it means lor something to be blank. So, the conceptual definition acquired can be regarded as a rule for composing the adjective's meaning and a noun's meaning, if one takes meaning paraphrases as rule descriptions. The rule covers conventionalized readings of &quot;blank&quot; (this supports an observation described in \[Boguraev/Pustejovsky 90\]). Used in texts, however, these readings undergo further changes (cf. \[Haenelt 92\]). So, e.g. a word can stepwise be related to a complex concept in a text and then be used as a term.</Paragraph> </Section> class="xml-element"></Paper>