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This paper presents a survey on the role of negation in sentiment analysis. Negation is a very common linguistic construction that affects polarity and, therefore, needs to be taken into consideration in sentiment analysis.
We will present various computational approaches modeling negation in sentiment analysis. We will, in particular, focus on aspects such as level of representation used for sentiment analysis, negation word detection and scope of negation. We will also discuss limits and challenges of negation modeling on that task.
This paper describes work directed towards the development of a syllable prominence-based prosody generation functionality for a German unit selection speech synthesis system. A general concept for syllable prominence-based prosody generation in unit selection synthesis is proposed. As a first step towards its implementation, an automated syllable prominence annotation procedure based on acoustic analyses has been performed on the BOSS speech corpus. The prominence labeling has been evaluated against an existing annotation of lexical stress levels and manual prominence labeling on a subset of the corpus. We discuss methods and results and give an outlook on further implementation steps.
Bootstrapping Supervised Machine-learning Polarity Classifiers with Rule-based Classification
(2010)
In this paper, we explore the effectiveness of bootstrapping supervised machine-learning polarity classifiers using the output of domain-independent rule-based classifiers. The benefit of this method is that no labeled training data are required. Still, this method allows to capture in-domain knowledge by training the supervised classifier on in-domain features, such as bag of words.
We investigate how important the quality of the rule-based classifier is and what features are useful for the supervised classifier. The former addresses the issue in how far relevant constructions for polarity classification, such as word sense disambiguation, negation modeling, or intensification, are important for this self-training approach. We not only compare how this method relates to conventional semi-supervised learning but also examine how it performs under more difficult settings in which classes are not balanced and mixed reviews are included in the dataset.
Active learning has been applied to different NLP tasks, with the aim of limiting the amount of time and cost for human annotation. Most studies on active learning have only simulated the annotation scenario, using prelabelled gold standard data. We present the first active learning experiment for Word Sense Disambiguation with human annotators in a realistic environment, using fine-grained sense distinctions, and investigate whether AL can reduce annotation cost and boost classifier performance when applied to a real-world task.
This paper describes the application of probabilistic part of speech taggers to the Dzongkha language. A tag set containing 66 tags is designed, which is based on the Penn Treebank. A training corpus of 40,247 tokens is utilized to train the model. Using the lexicon extracted from the training corpus and lexicon from the available word list, we used two statistical taggers for comparison reasons. The best result achieved was 93.1% accuracy in a 10-fold cross validation on the training set. The winning tagger was thereafter applied to annotate a 570,247 token corpus.
This paper shows how corpora and related tools can be used to analyse and present significant colligational patterns lexicographically. In German, patterns such as das nötige Wissen vermitteln and sein Wissen unter Beweis stellen play a vital role when learning the language, as they exhibit relevant idiomatic usage and lexical and syntactic rules of combination. Each item has specific semantic and grammatical functions and particular preferences with respect to position and distribution. An analysis of adjectives, for example, identifies preferences in adverbial, attributive, or predicative functions.
Traditionally, corpus analyses of syntagmatic constructions have not been conducted for lexicographic purposes. This paper shows how to utilise corpora to extract and examine typical syntagms and how the results of such an analysis are documented systematically in ELEXIKO, a large-scale corpus-based Internet reference work of German. It also demonstrates how this dictionary accounts for the lexical and grammatical interplay between units in a syntagm and how authentic corpus material and complementary prose-style usage notes are a useful guide to text production or reception.
Opinion holder extraction is one of the important subtasks in sentiment analysis. The effective detection of an opinion holder depends on the consideration of various cues on various levels of representation, though they are hard to formulate explicitly as features. In this work, we propose to use convolution kernels for that task which identify meaningful fragments of sequences or trees by themselves. We not only investigate how different levels of information can be effectively combined in different kernels but also examine how the scope of these kernels should be chosen. In general relation extraction, the two candidate entities thought to be involved in a relation are commonly chosen to be the boundaries of sequences and trees. The definition of boundaries in opinion holder extraction, however, is less straightforward since there might be several expressions beside the candidate opinion holder to be eligible for being a boundary.
Corpus-based identification and disambiguation of reading indicators for German nominalizations
(2010)
Corpus data is often structurally and lexically ambiguous; corpus extraction methodologies thus must be made aware of ambiguities. Therefore, given an extraction task, all relevant ambiguities must be identified. To resolve these ambiguities, contextual data responsible for one or another reading is to be considered. In the context of our present work, German -ung-nominalizations and their sortal readings are under examination. A number of these nominalizations may be read as an event or a result, depending on the semantic group they belong to. Here, we concentrate on nominalizations of verbs of saying (henceforth: "verba dicendi"), identify their context partners and their influence on the sortal reading of the nominalizations in question. We present a tool which calculates the sortal reading of such nominalizations and thus may improve not only corpus extraction, but also e.g. machine translation. Lastly, we describe successful attempts to identify the correct sortal reading, conclusions and future work.
This paper describes general requirements for evaluating and documenting NLP tools with a focus on morphological analysers and the design of a Gold Standard. It is argued that any evaluation must be measurable and documentation thereof must be made accessible for any user of the tool. The documentation must be of a kind that it enables the user to compare different tools offering the same service, hence the descriptions must contain measurable values. A Gold Standard presents a vital part of any measurable evaluation process, therefore, the corpus-based design of a Gold Standard, its creation and problems that occur are reported upon here. Our project concentrates on SMOR, a morphological analyser for German that is to be offered as a web-service. We not only utilize this analyser for designing the Gold Standard, but also evaluate the tool itself at the same time. Note that the project is ongoing, therefore, we cannot present final results.
This paper provides a new generation of a markup language by introducing the Freestyle Markup Language (FML). Demands placed on the language are elaborated, considering current standards and discussions. Conception, a grammatical definition, a corresponding object graph and the bi-directional unambiguous transformation between these two congruent representation forms are set up. The result of this paper is a fundamental definition of a completely new markup language, consolidating many deficiency-discourses and experiences into one particular implementation concept, encouraging the evolution of markup.
We present a method and a software tool, the FrameNet Transformer, for deriving customized versions of the FrameNet database based on frame and frame element relations. The FrameNet Transformer allows users to iteratively coarsen the FrameNet sense inventory in two ways. First, the tool can merge entire frames that are related by user-specified relations. Second, it can merge word senses that belong to frames related by specified relations. Both methods can be interleaved. The Transformer automatically outputs format-compliant FrameNet versions, including modified corpus annotation files that can be used for automatic processing. The customized FrameNet versions can be used to determine which granularity is suitable for particular applications. In our evaluation of the tool, we show that our method increases accuracy of statistical semantic parsers by reducing the number of word-senses (frames) per lemma, and increasing the number of annotated sentences per lexical unit and frame. We further show in an experiment on the FATE corpus that by coarsening FrameNet we do not incur a significant loss of information that is relevant to the Recognizing Textual Entailment task.
This paper discusses the advantages and disadvantages of the combination of automated information and lexicographically interpreted information in online dictionaries, namely elexiko, a hypertext dictionary and lexical data information system of contemporary German (http://www.owid.de/ elexiko_/index.html), and DWDS, a digital dictionary of 20,h century German (http://www.dwds.de). Examples of automatically derived information (e.g. automatically extracted citations from the underlying corpus, lists on paradigmatic relations) and lexicographically compiled information (e.g. information on paradigmatic partners) are provided and evaluated, reflecting on the need to develop guidelines as to how computerised information and lexicographically interpreted information may be combined profitably in online reference works.
The Online-Wortschatz-Informationssystem Deutsch (OWID Online German Lexical Information System) is a lexicographic Internet portal for various electronic dictionary resources that are being compiled at the Institute for the German Language (Institut für Deutsche Sprache, IDS). The main emphasis of OWID is on academic lexicographic resources of contemporary German. Presently, the following dictionaries are included in OWID: a dictionary of contemporary German called elexiko, a dictionary of neologisms, a small dictionary of collocations, and a discourse dictionary covering the lexemes that establish the discourse about “guilt” in the early post-war era 1945-1955. In the near future (2010/2011), several additional dictionaries will be published in OWID: a Textbook of German Communication Verbs, a Valency Dictionary of German Verbs, two further discourse dictionaries – one about the “democracy” discourse around 1968, the other covering the keywords of the German reunification 1989/1990. Moreover, 300 entries from a corpus-based project on proverbs will be integrated into OWID. Thereby, OWID is a constantly growing resource for academic lexicographic work of the German language.
Altogether, OWID is a special kind of dictionary portal owing to its content and its design, namely the integration of the various dictionaries, the access possibilities and the presentation features. With OWID, we try to establish a dictionary net where the different resources are jointly accessible not only by headwords, but also on the microstructural level. Prerequisite for these common access- and navigation-possibilities across the various dictionaries is the same concept for the lexicographic data model which we put into practice in OWID. Data from all dictionaries in OWID are structured according to a tailor-made, fine-granular, XML-based data model. In this data model, similar content is modelled similarly, dictionary related differences are preserved.
The main tasks for the future are to enhance OWID with further dictionary resources, to improve the inner access structures so that they exhaust the possibilities of the data model, and to customize the layout of the dictionaries as well as the search options according to the user’s needs
Empirical synchronic language studies generally seek to investigate language phenomena for one point in time, even though this point in time is often not stated explicitly. Until today, surprisingly little research has addressed the implications of this time-dependency of synchronic research on the composition and analysis of data that are suitable for conducting such studies. Existing solutions and practices tend to be too general to meet the needs of all kinds of research questions. In this theoretical paper that is targeted at both corpus creators and corpus users, we propose to take a decidedly synchronic perspective on the relevant language data. Such a perspective may be realised either in terms of sampling criteria or in terms of analytical methods applied to the data. As a general approach for both realisations, we introduce and explore the FReD strategy (Frequency Relevance Decay) which models the relevance of language events from a synchronic perspective. This general strategy represents a whole family of synchronic perspectives that may be customised to meet the requirements imposed by the specific research questions and language domain under investigation.
We describe the SemEval-2010 shared task on “Linking Events and Their Participants in Discourse”. This task is an extension to the classical semantic role labeling task. While semantic role labeling is traditionally viewed as a sentence-internal task, local semantic argument structures clearly interact with each other in a larger context, e.g., by sharing references to specific discourse entities or events. In the shared task we looked at one particular aspect of cross-sentence links between argument structures, namely linking locally uninstantiated roles to their co-referents in the wider discourse context (if such co-referents exist). This task is potentially beneficial for a number of NLP applications, such as information extraction, question answering or text summarization.
Historical cabinet protocols are a useful resource which enable historians to identify the opinions expressed by politicians on different subjects and at different points of time. While cabinet protocols are often available in digitized form, so far the only method to access their information content is by keyword-based search, which often returns sub-optimal results. We present a method for enriching German cabinet protocols with information about the originators of statements. This requires automatic speaker attribution. In order to avoid costly manual annotation of training data, we design a rule-based system which exploits morpho-syntactic cues. Unlike many other approaches, our method can also deal with cases in which the speaker is not explicitly identified in the sentence itself. This is an important capability as 45% of all sentences in the data constitute reported speech whose speakers are not explicitly marked. Our system is able to detect implicit speakers by taking into account signals of speaker continuity. We show that such a system obtains good results, especially with respect to recall which is particularly important for information access.
This paper describes the efforts in the field of sustainability of the Institut für Deutsche Sprache (IDS) in Mannheim with respect to DEREKO (Deutsches Referenzkorpus) the Archive of General Reference Corpora of Contemporary Written German. With focus on re-usability and sustainability, we discuss its history and our future plans. We describe legal challenges related to the creation of a large and sustainable resource; sketch out the pipeline used to convert raw texts to the final corpus format and outline migration plans to TEI P5. Due to the fact, that the current version of the corpus management and query system is pushed towards its limits, we discuss the requirements for a new version which will be able to handle current and future DEREKO releases. Furthermore, we outline the institute’s plans in the field of digital preservation.
So far, comprehensive grammar descriptions of Northern Sotho have only been available in the form of prescriptive books aiming at teaching the language. This paper describes parts of the first morpho-syntactic description of Northern Sotho from a computational perspective (Faaß, 2010a). Such a description is necessary for implementing rule based, operational grammars. It is also essential for the annotation of training data to be utilised by statistical parsers. The work that we partially present here may hence provide a resource for computational processing of the language in order to proceed with producing linguistic representations beyond tagging, may it be chunking or parsing. The paper begins with describing significant Northern Sotho verbal morpho-syntactics (section 2). It is shown that the topology of the verb can be depicted as a slot system which may form the basis for computational processing (section 3). Note that the implementation of the described rules (section 4) and also coverage tests are ongoing processes upon that we will report in more detail at a later stage.
In the paper we investigate the impact of data size on a Word Sense Disambiguation task (WSD). We question the assumption that the knowledge acquisition bottleneck, which is known as one of the major challenges for WSD, can be solved by simply obtaining more and more training data. Our case study on 1,000 manually annotated instances of the German verb drohen (threaten) shows that the best performance is not obtained when training on the full data set, but by carefully selecting new training instances with regard to their informativeness for the learning process (Active Learning). We present a thorough evaluation of the impact of different sampling methods on the data sets and propose an improved method for uncertainty sampling which dynamically adapts the selection of new instances to the learning progress of the classifier, resulting in more robust results during the initial stages of learning. A qualitative error analysis identifies problems for automatic WSD and discusses the reasons for the great gap in performance between human annotators and our automatic WSD system.