Opinion mining with the SentWordNet lexical resource

Sentiment classification concerns the application of automatic methods for predicting the orientation of sentiment present on text documents. It is an important subject in opinion mining research, with applications on a number of areas including recommender and advertising systems, customer intelligence and information retrieval. SentiWordNet is a lexical resource of sentiment information for terms in the English language designed to assist in opinion mining tasks, where each term is associated with numerical scores for positive and negative sentiment information. A resource that makes term level sentiment information readily available could be of use in building more effective sentiment classification methods. This research presents the results of an experiment that applied the SentiWordNet lexical resource to the problem of automatic sentiment classification of film reviews. First, a data set of relevant features extracted from text documents using SentiWordNet was designed and implemented. The resulting feature set is then used as input for training a support vector machine classifier for predicting the sentiment orientation of the underlying film review. Several scenarios exploring variations on the parameters that generate the data set, outlier removal and feature selection were executed. The results obtained are compared to other methods documented in the literature. It was found that they are in line with other experiments that propose similar approaches and use the same data set of film reviews, indicating SentiWordNet could become an important resource for the task of sentiment classification. Considerations on future improvements are also presented based on a detailed analysis of classification results

Real-Time Topic and Sentiment Analysis in Human-Robot Conversation

Socially interactive robots, especially those designed for entertainment and companionship, must be able to hold conversations with users that feel natural and engaging for humans. Two important components of such conversations include adherence to the topic of conversation and inclusion of affective expressions. Most previous approaches have concentrated on topic detection or sentiment analysis alone, and approaches that attempt to address both are limited by domain and by type of reply. This thesis presents a new approach, implemented on a humanoid robot interface, that detects the topic and sentiment of a user’s utterances from text-transcribed speech. It also generates domain-independent, topically relevant verbal replies and appropriate positive and negative emotional expressions in real time. The front end of the system is a smartphone app that functions as the robot’s face. It displays emotionally expressive eyes, transcribes verbal input as text, and synthesizes spoken replies. The back end of the system is implemented on the robot’s onboard computer. It connects with the app via Bluetooth, receives and processes the transcribed input, and returns verbal replies and sentiment scores. The back end consists of a topic-detection subsystem and a sentiment-analysis subsystem. The topic-detection subsystem uses a Latent Semantic Indexing model of a conversation corpus, followed by a search in the online database ConceptNet 5, in order to generate a topically relevant reply. The sentiment-analysis subsystem disambiguates the input words, obtains their sentiment scores from SentiWordNet, and returns the averaged sum of the scores as the overall sentiment score. The system was hypothesized to engage users more with both subsystems working together than either subsystem alone, and each subsystem alone was hypothesized to engage users more than a random control. In computational evaluations, each subsystem performed weakly but positively. In user evaluations, users reported a higher level of topical relevance and emotional appropriateness in conversations in which the subsystems were working together, and they reported higher engagement especially in conversations in which the topic-detection system was working. It is concluded that the system partially fulfills its goals, and suggestions for future work are presented

Role of semantic indexing for text classification.

The Vector Space Model (VSM) of text representation suffers a number of limitations for text classification. Firstly, the VSM is based on the Bag-Of-Words (BOW) assumption where terms from the indexing vocabulary are treated independently of one another. However, the expressiveness of natural language means that lexically different terms often have related or even identical meanings. Thus, failure to take into account the semantic relatedness between terms means that document similarity is not properly captured in the VSM. To address this problem, semantic indexing approaches have been proposed for modelling the semantic relatedness between terms in document representations. Accordingly, in this thesis, we empirically review the impact of semantic indexing on text classification. This empirical review allows us to answer one important question: how beneficial is semantic indexing to text classification performance. We also carry out a detailed analysis of the semantic indexing process which allows us to identify reasons why semantic indexing may lead to poor text classification performance. Based on our findings, we propose a semantic indexing framework called Relevance Weighted Semantic Indexing (RWSI) that addresses the limitations identified in our analysis. RWSI uses relevance weights of terms to improve the semantic indexing of documents. A second problem with the VSM is the lack of supervision in the process of creating document representations. This arises from the fact that the VSM was originally designed for unsupervised document retrieval. An important feature of effective document representations is the ability to discriminate between relevant and non-relevant documents. For text classification, relevance information is explicitly available in the form of document class labels. Thus, more effective document vectors can be derived in a supervised manner by taking advantage of available class knowledge. Accordingly, we investigate approaches for utilising class knowledge for supervised indexing of documents. Firstly, we demonstrate how the RWSI framework can be utilised for assigning supervised weights to terms for supervised document indexing. Secondly, we present an approach called Supervised Sub-Spacing (S3) for supervised semantic indexing of documents. A further limitation of the standard VSM is that an indexing vocabulary that consists only of terms from the document collection is used for document representation. This is based on the assumption that terms alone are sufficient to model the meaning of text documents. However for certain classification tasks, terms are insufficient to adequately model the semantics needed for accurate document classification. A solution is to index documents using semantically rich concepts. Accordingly, we present an event extraction framework called Rule-Based Event Extractor (RUBEE) for identifying and utilising event information for concept-based indexing of incident reports. We also demonstrate how certain attributes of these events e.g. negation, can be taken into consideration to distinguish between documents that describe the occurrence of an event, and those that mention the non-occurrence of that event

Learning domain-specific sentiment lexicons with applications to recommender systems

Search is now going beyond looking for factual information, and people wish to search for the opinions of others to help them in their own decision-making. Sentiment expressions or opinion expressions are used by users to express their opinion and embody important pieces of information, particularly in online commerce. The main problem that the present dissertation addresses is how to model text to find meaningful words that express a sentiment. In this context, I investigate the viability of automatically generating a sentiment lexicon for opinion retrieval and sentiment classification applications. For this research objective we propose to capture sentiment words that are derived from online users’ reviews. In this approach, we tackle a major challenge in sentiment analysis which is the detection of words that express subjective preference and domain-specific sentiment words such as jargon. To this aim we present a fully generative method that automatically learns a domain-specific lexicon and is fully independent of external sources. Sentiment lexicons can be applied in a broad set of applications, however popular recommendation algorithms have somehow been disconnected from sentiment analysis. Therefore, we present a study that explores the viability of applying sentiment analysis techniques to infer ratings in a recommendation algorithm. Furthermore, entities’ reputation is intrinsically associated with sentiment words that have a positive or negative relation with those entities. Hence, is provided a study that observes the viability of using a domain-specific lexicon to compute entities reputation. Finally, a recommendation system algorithm is improved with the use of sentiment-based ratings and entities reputation

A New Hybrid Approach to Sentiment Classification

With the advancement of the World Wide Web, opinion sharing online has gained a lot of popularity. These opinions are utilized for decision making, market analysis, as well as other applications. The need to harness these opinions, and the motivation behind this need has led to the development and subsequent advancement of the field of Sentiment Analysis. Various issues have arisen from these, such as difficulty in locating these opinions in a body of text, as well as determining the sentiment/polarity of these opinions. To tackle the issue of opinion polarity determination, a number of classification approaches have been developed. These approaches have focused on opinion classification at various levels, such as document, sentence and aspect levels. Most document level approaches treat documents as a bag of words during the classification process, and hence classify them as a whole. The problem with this is that there could be a mixture of opinions directed towards various aspects, within a document. It is therefore imperative to utilize a classification approach which takes into account these constituent opinions. This is the focus of classification approaches which work at the aspect level. Another important factor in the issue of sentiment/polarity classification is the choice of the classification approach. This can be machine learning, lexical/lexicon-based, and more recently, hybrid. The machine learning approaches have the benefits of carrying out classification with high accuracies, and efficiently handling large feature sets, which makes them a favourite choice where high accuracies are desired. They however also have the drawback of difficulty in adaptability, due to the domain dependency of sentiment words. The pure lexicon-based approaches do not achieve the accuracy of the machine learning approaches, but are said to offer more explainable results and take into consideration the information in lexicons. In this work, we present a novel hybrid approach, which incorporates information from lexicons in a machine learning classifier, and takes as features various linguistic knowledge sources. Our novel hybrid approach utilizes transitive dependencies to incorporate the opinions expressed towards different aspects of a document in determining the polarity classification of the whole document. The domain dependency of sentiment words is also addressed through the use of composite features and a domain specific lexicon created in this work. It was found that the use of transitive dependencies in an aspect-focused classification is a promising area, which has the potential of improving aspect based classification once the aspects have been properly determined. It was also found that although using composite features does not necessarily improve the classification accuracy, it gives rise to context rich classifiers, and the domain specific lexicon generated performed on par with the widely used generic lexicon, SentiWordNet

Investigation into the Application of Personality Insights and Language Tone Analysis in Spam Classification

Due to its persistence spam remains as one of the biggest problems facing users and suppliers of email communication services. Machine learning techniques have been very successful at preventing many spam mails from arriving in user mailboxes, however they still account for over 50% of all emails sent. Despite this relative success the economic cost of spam has been estimated as high as $50 billion in 2005 and more recently at$20 billion so spam can still be considered a considerable problem. In essence a spam email is a commercial communication trying to entice the receiver to take some positive action. This project uses the text from emails and creates personality insight and language tone scores through the use of IBM Watsons’ Tone Analyzer API. Those scores are used to investigate whether the language used in emails can be transformed into useful features that can be used to correctly classify them as spam or genuine emails. And during the course of this investigation a range of machine learning techniques are applied. Results from this experiment found that where just the personality insight and language tone features are used in the model some promising results with one dataset were shown. However over all datasets results were inconclusive with this model. Furthermore it was found that in a model where these features were used in combination with a normalised term-frequency feature-set no real improvement in the classification performance was shown

Data properties and the performance of sentiment classification for electronic commerce applications

Sentiment classification has played an important role in various research area including e-commerce applications and a number of advanced Computational Intelligence techniques including machine learning and computational linguistics have been proposed in the literature for improved sentiment classification results. While such studies focus on improving performance with new techniques or extending existing algorithms based on previously used dataset, few studies provide practitioners with insight on what techniques are better for their datasets that have different properties. This paper applies four different sentiment classification techniques from machine learning (Naïve Bayes, SVM and Decision Tree) and sentiment orientation approaches to datasets obtained from various sources (IMDB, Twitter, Hotel review, and Amazon review datasets) to learn how different data properties including dataset size, length of target documents, and subjectivity of data affect the performance of those techniques. The results of computational experiments confirm the sensitivity of the techniques on data properties including training data size, the document length and subjectivity of training /test data in the improvement of performances of techniques. The theoretical and practical implications of the findings are discussed.This study was partially funded by Korea National Research Foundation through Global Research Network Program (Project no. 2016S1A2A2912265) and EU funded project Policy Compass (Project no. 283700)

Machine learning and sentiment analysis approaches for the analysis of Parliamentary debates

In this thesis the author seeks to establish the most appropriate mechanism for conducting sentiment analysis with respect to political debates; firstly so as to predict their outcome and secondly to support a mechanism to provide for the visualisation of such debates in the context of further analysis. To this end two alternative approaches are considered, a classification-based approach and a lexicon-based approach. In the context of the second approach both generic and domain specific sentiment lexicons are considered. Two techniques to generating domain-specific sentiment lexicons are also proposed: (i) direct generation and (ii) adaptation. The first was founded on the idea of generating a dedicated lexicon directly from labelled source data. The second approach was founded on the idea of using an existing general purpose lexicon and adapting this so that it becomes a specialised lexicon with respect to some domain. The operation of both the generic and domain specific sentiment lexicons are compared with the classification-based approach. The comparison between the potential sentiment mining approaches was conducted by predicting the attitude of individual debaters (speakers) in political debates (using a corpus of labelled political speeches extracted from political debate transcripts taken from the proceedings of the UK House of Commons). The reported comparison indicates that the attitude of speakers can be effectively predicted using sentiment mining. The author then goes on to propose a framework, the Debate Graph Extraction (DGE) framework, for extracting debate graphs from transcripts of political debates. The idea is to represent the structure of a debate as a graph with speakers as nodes and “exchanges” as links. Links between nodes were established according to the exchanges between the speeches. Nodes were labelled according to the “attitude” (sentiment) of the speakers, “positive” or “negative”, using one of the three proposed sentiment mining approaches. The attitude of the speakers was then used to label the graph links as being either “supporting” or “opposing”. If both speakers had the same attitude (both “positive” or both “negative”) the link was labelled as being “supporting”; otherwise the link was labelled as being “opposing”. The resulting graphs capture the abstract representation of a debate where two opposing factions exchange arguments on related content. Finally, the author moves to discuss mechanisms whereby debate graphs can be structurally analysed using network mathematics and community detection techniques. To this end the debate graphs were conceptualised as networks in order to conduct appropriate network analysis. The significance was that the network mathematics and community detection processes can draw conclusions about the general properties of debates in parliamentary practice through the exploration of the embedded patterns of connectivity and reactivity between the exchanging nodes (speakers)

Semantic Sentiment Analysis of Microblogs

Microblogs and social media platforms are now considered among the most popular forms of online communication. Through a platform like Twitter, much information reflecting people's opinions and attitudes is published and shared among users on a daily basis. This has recently brought great opportunities to companies interested in tracking and monitoring the reputation of their brands and businesses, and to policy makers and politicians to support their assessment of public opinions about their policies or political issues. A wide range of approaches to sentiment analysis on Twitter, and other similar microblogging platforms, have been recently built. Most of these approaches rely mainly on the presence of affect words or syntactic structures that explicitly and unambiguously reflect sentiment (e.g., "great'', "terrible''). However, these approaches are semantically weak, that is, they do not account for the semantics of words when detecting their sentiment in text. This is problematic since the sentiment of words, in many cases, is associated with their semantics, either along the context they occur within (e.g., "great'' is negative in the context "pain'') or the conceptual meaning associated with the words (e.g., "Ebola" is negative when its associated semantic concept is "Virus"). This thesis investigates the role of words' semantics in sentiment analysis of microblogs, aiming mainly at addressing the above problem. In particular, Twitter is used as a case study of microblogging platforms to investigate whether capturing the sentiment of words with respect to their semantics leads to more accurate sentiment analysis models on Twitter. To this end, several approaches are proposed in this thesis for extracting and incorporating two types of word semantics for sentiment analysis: contextual semantics (i.e., semantics captured from words' co-occurrences) and conceptual semantics (i.e., semantics extracted from external knowledge sources). Experiments are conducted with both types of semantics by assessing their impact in three popular sentiment analysis tasks on Twitter; entity-level sentiment analysis, tweet-level sentiment analysis and context-sensitive sentiment lexicon adaptation. Evaluation under each sentiment analysis task includes several sentiment lexicons, and up to 9 Twitter datasets of different characteristics, as well as comparing against several state-of-the-art sentiment analysis approaches widely used in the literature. The findings from this body of work demonstrate the value of using semantics in sentiment analysis on Twitter. The proposed approaches, which consider words' semantics for sentiment analysis at both, entity and tweet levels, surpass non-semantic approaches in most datasets

A Survey of Sentiment Analysis and Sarcasm Detection: Challenges, Techniques, and Trends

In recent years, more people have been using the internet and social media to express their opinions on various subjects, such as institutions, services, or specific ideas. This increase highlights the importance of developing automated tools for accurate sentiment analysis. Moreover, addressing sarcasm in text is crucial, as it can significantly impact the efficacy of sentiment analysis models. This paper aims to provide a comprehensive overview of the conducted research on sentiment analysis and sarcasm detection, focusing on the time from 2018 to 2023. It explores the challenges faced and the methods used to address them. It conducts a comparison of these methods. It also aims to identify emerging trends that will likely influence the future of sentiment analysis and sarcasm detection, ensuring their continued effectiveness. This paper enhances the existing knowledge by offering a comprehensive analysis of 40 research works, evaluating performance, addressing multilingual challenges, and highlighting future trends in sarcasm detection and sentiment analysis. It is a valuable resource for researchers and experts interested in the field, facilitating further advancements in sentiment analysis techniques and applications. It categorizes sentiment analysis methods into ML, lexical, and hybrid approaches, highlighting deep learning, especially Recurrent Neural Networks (RNNs), for effective textual classification with labeled or unlabeled data