it needs to be ensured that the inability to complete the 135 sentences, most of which longer than the average in the corpus subset, was not caused by a memory leak as this could nullify the benefits expected from further grammar development.
With respect to the selection of linguistic stimuli for the further study of our model’s context-integration behaviour, we conclude that the selection of arbitrary linguistic stimuli from a corpus of unrestricted natural language is not a viable option with the present version of the role-assigning grammar. To be able to predict and analyse our model’s context integration behaviour systematically, we hence need to study context integration on sentences for which correct syntactic and semantic analysis has been ensured prior to context integration. The following section discusses the selection of suitable linguistic input for our context integration investigations in the subsequent chapters.
main clause and a subclause. In a subset of the extracted sentences the sub-clause contained a global genitive-dative ambiguity. With our focus on context-induced resolution of syntactic ambiguity, we normalised the introductory main clauses to be the same in all sentences. Normalisation of the introductory main clauses resulted in a reduction of the total number of unique sentences after the removal of duplicate sentences.
VK-274 ‘Er wusste, dass die Doktorandin der Forscherin den Beweis lieferte.’
He knew that
(the researcher’s PhD student delivered the evidence. ) the PhD student delivered the evidence to the researcher.
Genitive Reading Forscherin SYN:GMOD, INST:OWNER
−−−−−−−−−−−−−−−−−−→ Doktorandin Dative Reading Forscherin SYN:OBJD,INST:RECIPIENT
−−−−−−−−−−−−−−−−−−→ lieferte
SO-9792 ‘Sie vertritt die Gesellschaft, und ihr obliegt die Gesch¨aftsf¨uhrung.’
(She represents the association, )
and management is her responsibility.
It is her that the association represents,
Subject-Object Reading sie −−−−−−−−−−−−−−−→SYN:SUBJ,AGNT:AGENT vertritt Gesellschaft−−−−−−−−−−−−−−−→SYN:OBJA,THME:THEME vertritt Object-Subject Reading sie −−−−−−−−−−−−−−−→SYN:OBJA,THME:THEME vertritt Gesellschaft−−−−−−−−−−−−−−−→SYN:SUBJ,AGNT:AGENT vertritt
PP-7177 ‘Insgesamt werden Braunkohlemeiler mit zusammen 8500 Megawatt (MW) abgeschaltet.’
Overall, lignite-fired plants
(with a total of 8,500 megawatts (MW) will be switched off.) will be switched off by a total of 8,500 megawatts (MW).
INSTRUMENTReading Megawatt−−−−−→SYN:PN mit −−−−−→SYN:PP abgeschaltet Megawatt INST:INSTRUMENT
−−−−−−−−−−−−−−−−→ abgeschaltet
COMITATIVE Reading Megawatt−−−−−→SYN:PN mit −−−−−→SYN:PP Braunkohlemeiler Megawatt INST:COMITATIVE
−−−−−−−−−−−−−−−−→ Braunkohlemeiler
Figure 8.2: Examples for the ambiguity types selected for study under context integration.
The selected sentences are parsed with WCDG2’s extended grammar under inte-gration of an empty context model (genitive-dative ambiguity in Experiment 1.2, subject-object ambiguity in Experiment 1.3, and PP-attachment ambiguity in Ex-periment 1.4). We test which of the extracted sentences are assigned a correct syntactic and semantic analysis by WCDG2’s extended grammar. ‘Correct’ in this context does not necessarily mean that the default analysis also represents the pre-ferred reading that human linguistic intuition would favour. Rather, ‘correct’ in this case expresses that the analysis of the sentence permits to construct a context in which the analysis represents a plausible reading of the sentence.
From the set of correctly analysed sentences we select three subsets of 10 sentences each for use in the subsequent context integration experiments. The selection cri-terion for the sentences in the subsets is that at least one of the two readings of the syntactic ambiguity, preferably even both, should correspond to a visually per-ceivable situation. Due to the extensive use of figurative language, especially in the newspaper articles of the SALSA corpus, this criterion turned out to be surprisingly difficult to fulfil. The three sets of selected sentences are listed in Appendices IV.1, IV.2, and IV.3, respectively. We henceforth refer to the parses obtained under inte-gration of an empty context model as default parses.
8.2.3 Results
Ten subject-object-ambiguous sentences were selected from a set of 1,813 sentences extracted from the SALSA corpus. The ten sentences with PP-attachment ambigu-ity were picked from an extract of 152 sentences that contained a ‘mit’-PP. From the cited psycholinguistic investigation we extracted 427 sentences. Normalisation of the introductory main clauses and subsequent removal of the resulting duplicate sentences reduced the number of sentences down to 337. A subset of these sen-tences exhibited global genitive-dative ambiguity from which we randomly selected ten sentences.
As a consequence of the selection criteria, all of the sentences in the three sub-sets had a syntactically and semantically ‘correct’ analysis in the sense laid out in Section 8.2.2. The genitive-dative ambiguous sentences all received the same struc-tural analysis which corresponds to the dative-reading and involves the ternary verb form. The corresponding generic tree structure is shown in Figure 8.3. The full list of parse trees for the genitive-dative-ambiguous sentences in the absence of a contextual bias is given in Appendix VI.1.1. The analyses for the sentences con-taining subject-object ambiguity and PP-attachment ambiguity do not exhibit a uniform preference pattern within each set. The parse trees for subject-object and PP-attachment ambiguities are listed in AppendicesVI.2.1and VI.3.1, respectively.
8.2.4 Discussion
The selected globally ambiguous sentences largely afford analyses in WCDG2 that also represent the reading favoured by human linguistic intuition. However, some of the solutions, though formally correct, represent a reading that differs from human linguistic intuition in the absence of a biasing context. As an example, consider
OBJC
OBJA DET
OBJD
DET SUBJ DET
KONJ S
SUBJ
Er wusste , dass Slot.5 Slot.6 Slot.7 Slot.8 Slot.9 Slot.10 Slot.11 .
AGENT THEME AGENT
THEME
RECIPIENT
Figure 8.3: Generic parse tree structure for the extracted genitive-dative-ambiguous sentences under integration of an empty visual context model (default analysis).
sentence SO-10744 ‘Beide Kriegsparteien dr¨angten sie, an den Verhandlungstisch zur¨uckzukehren.’ It was both war parties that they urged to return to the negotiat-ing table. This sentence parses as the subject-object analysis by default: Both war parties urged them to return to the negotiating table. While this analysis is clearly possible, it is certainly the less likely reading in the absence of a biasing context.
Based on world-knowledge we know that negotiations can be an alternative means of conflict resolution for warring parties; we hence would assume that it was the war parties that were urged to return to the negotiating table. Since the analyses of the sentences in this experiment have been obtained under integration of an empty context model, i.e., in the absence of a visual context bias, they are a direct reflec-tion of the linguistic preferences encoded in the extended grammar. In this case, the preference of the subject-before-object word order dominated the entire analysis.
The evaluation of the semantic grammar on the 1,000 NEGRA sentences in Ex-periment 1.1 showed that the extended grammar fails to meet Requirement R7 for the neutrality of referentially unrelated visual context on unrestricted input. The selection of the sentences in Experiments 1.2 to 1.4 was made to ensure that our model meets Requirement R7 at least for the selected sentences. We hence rate Requirement R7 as partially fulfilled by our model. As illustrated by the low recall values obtained in the validation of the extended grammar on unrestricted input in Experiment 1.1, the full satisfaction of this requirement necessitates a substantial extension of the grammar’s coverage.