Using Brain Data for Sentiment Analysis

We present the results of exploratory experiments using lexical valence extracted from brain using electroencephalography (EEG) for sentiment analysis. We selected 78 English words (36 for training and 42 for testing), presented as stimuli to 3 English native speakers. EEG signals were recorded from the subjects while they performed a mental imaging task for each word stimulus. Wavelet decomposition was employed to extract EEG features from the time-frequency domain. The extracted features were used as inputs to a sparse multinomial logistic regression (SMLR) classifier for valence classification, after univariate ANOVA feature selection. After mapping EEG signals to sentiment valences, we exploited the lexical polarity extracted from brain data for the prediction of the valence of 12 sentences taken from the SemEval-2007 shared task, and compared it against existing lexical resources.

Can(Plan)+: Extending the Operational Semantics of the BDI Architecture to deal with Uncertain Information

The BDI architecture, where agents are modelled based on their beliefs, desires and intentions, provides a practical approach to develop large scale systems. However, it is not well suited to model complex Supervisory Control And Data Acquisition (SCADA) systems pervaded by uncertainty. In this paper we address this issue by extending the operational semantics of Can(Plan) into Can(Plan)+. We start by modelling the beliefs of an agent as a set of epistemic states where each state, possibly using a different representation, models part of the agent's beliefs. These epistemic states are stratified to make them commensurable and to reason about the uncertain beliefs of the agent. The syntax and semantics of a BDI agent are extended accordingly and we identify fragments with computationally efficient semantics. Finally, we examine how primitive actions are affected by uncertainty and we define an appropriate form of lookahead planning.

Resilience

Over the past decade the concept of ‘resilience’ has been mobilised across an increasingly wide range of policy arenas. For example, it has featured prominently within recent discussions on the nature of warfare, the purpose of urban and regional planning, the effectiveness of development policies, the intent of welfare reform and the stability of the international financial system. The term’s origins can be traced back to the work of the ecologist Crawford S. Holling and his formulation of a science of complexity. This paper reflects on the origins of these ideas and their travels from the field of natural resource management, which it now dominates, to contemporary social practices and policy arenas. It reflects on the ways in which a lexicon of complex adaptive systems, grounded in an epistemology of limited knowledge and uncertain futures, seeks to displace ongoing ‘dependence’ on professionals by valorising self-reliance and responsibility as techniques to be applied by subjects in the making of the resilient self. In so doing, resilience is being mobilised to govern a wide range of threats and sources of uncertainty, from climate change, financial crises and terrorism, to the sustainability of development, the financing of welfare and providing for an aging population. As such, ‘resilience’ risks becoming a measure of its subjects’ ‘fitness’ to survive in what are pre-figured as natural, turbulent orders of things.

Operators for Similarity Search: Semantics, Techniques and Usage Scenarios

This book provides a comprehensive tutorial on similarity operators. The authors systematically survey the set of similarity operators, primarily focusing on their semantics, while also touching upon mechanisms for processing them effectively.

The book starts off by providing introductory material on similarity search systems, highlighting the central role of similarity operators in such systems. This is followed by a systematic categorized overview of the variety of similarity operators that have been proposed in literature over the last two decades, including advanced operators such as RkNN, Reverse k-Ranks, Skyline k-Groups and K-N-Match. Since indexing is a core technology in the practical implementation of similarity operators, various indexing mechanisms are summarized. Finally, current research challenges are outlined, so as to enable interested readers to identify potential directions for future investigations.

In summary, this book offers a comprehensive overview of the field of similarity search operators, allowing readers to understand the area of similarity operators as it stands today, and in addition providing them with the background needed to understand recent novel approaches.

Semantics for possibilistic answer set programs: uncertain rules versus rules with uncertain conclusions

Although Answer Set Programming (ASP) is a powerful framework for declarative problem solving, it cannot in an intuitive way handle situations in which some rules are uncertain, or in which it is more important to satisfy some constraints than others. Possibilistic ASP (PASP) is a natural extension of ASP in which certainty weights are associated with each rule. In this paper we contrast two different views on interpreting the weights attached to rules. Under the first view, weights reflect the certainty with which we can conclude the head of a rule when its body is satisfied. Under the second view, weights reflect the certainty that a given rule restricts the considered epistemic states of an agent in a valid way, i.e. it is the certainty that the rule itself is correct. The first view gives rise to a set of weighted answer sets, whereas the second view gives rise to a weighted set of classical answer sets.

Characterizing and Extending Answer Set Semantics using Possibility Theory

Answer Set Programming (ASP) is a popular framework for modelling combinatorial problems. However, ASP cannot be used easily for reasoning about uncertain information. Possibilistic ASP (PASP) is an extension of ASP that combines possibilistic logic and ASP. In PASP a weight is associated with each rule, whereas this weight is interpreted as the certainty with which the conclusion can be established when the body is known to hold. As such, it allows us to model and reason about uncertain information in an intuitive way. In this paper we present new semantics for PASP in which rules are interpreted as constraints on possibility distributions. Special models of these constraints are then identified as possibilistic answer sets. In addition, since ASP is a special case of PASP in which all the rules are entirely certain, we obtain a new characterization of ASP in terms of constraints on possibility distributions. This allows us to uncover a new form of disjunction, called weak disjunction, that has not been previously considered in the literature. In addition to introducing and motivating the semantics of weak disjunction, we also pinpoint its computational complexity. In particular, while the complexity of most reasoning tasks coincides with standard disjunctive ASP, we find that brave reasoning for programs with weak disjunctions is easier.

Generating a Word-Emotion Lexicon from #Emotional Tweets

Research in emotion analysis of text suggest that emotion lexicon based features are superior to corpus based n-gram features. However the static nature of the general purpose emotion lexicons make them less suited to social media analysis, where the need to adopt to changes in vocabulary usage and context is crucial. In this paper we propose a set of methods to extract a word-emotion lexicon automatically from an emotion labelled corpus of tweets. Our results confirm that the features derived from these lexicons outperform the standard Bag-of-words features when applied to an emotion classification task. Furthermore, a comparative analysis with both manually crafted lexicons and a state-of-the-art lexicon generated using Point-Wise Mutual Information, show that the lexicons generated from the proposed methods lead to significantly better classi- fication performance.

Unsupervised Solution Post Identification from Discussion Forums

Discussion forums have evolved into a dependablesource of knowledge to solvecommon problems. However, only a minorityof the posts in discussion forumsare solution posts. Identifying solutionposts from discussion forums, hence, is animportant research problem. In this paper,we present a technique for unsupervisedsolution post identification leveraginga so far unexplored textual feature, thatof lexical correlations between problemsand solutions. We use translation modelsand language models to exploit lexicalcorrelations and solution post characterrespectively. Our technique is designedto not rely much on structural featuressuch as post metadata since suchfeatures are often not uniformly availableacross forums. Our clustering-based iterativesolution identification approach basedon the EM-formulation performs favorablyin an empirical evaluation, beatingthe only unsupervised solution identificationtechnique from literature by a verylarge margin. We also show that our unsupervisedtechnique is competitive againstmethods that require supervision, outperformingone such technique comfortably.

Two-part Segmentation of Text Documents

We consider the problem of segmenting text documents that have a
two-part structure such as a problem part and a solution part. Documents
of this genre include incident reports that typically involve
description of events relating to a problem followed by those pertaining
to the solution that was tried. Segmenting such documents
into the component two parts would render them usable in knowledge
reuse frameworks such as Case-Based Reasoning. This segmentation
problem presents a hard case for traditional text segmentation
due to the lexical inter-relatedness of the segments. We develop
a two-part segmentation technique that can harness a corpus
of similar documents to model the behavior of the two segments
and their inter-relatedness using language models and translation
models respectively. In particular, we use separate language models
for the problem and solution segment types, whereas the interrelatedness
between segment types is modeled using an IBM Model
1 translation model. We model documents as being generated starting
from the problem part that comprises of words sampled from
the problem language model, followed by the solution part whose
words are sampled either from the solution language model or from
a translation model conditioned on the words already chosen in the
problem part. We show, through an extensive set of experiments on
real-world data, that our approach outperforms the state-of-the-art
text segmentation algorithms in the accuracy of segmentation, and
that such improved accuracy translates well to improved usability
in Case-based Reasoning systems. We also analyze the robustness
of our technique to varying amounts and types of noise and empirically
illustrate that our technique is quite noise tolerant, and
degrades gracefully with increasing amounts of noise

Retrieving Similar Discussion Forum Threads: A Structure based Approach

Online forums are becoming a popular way of finding useful
information on the web. Search over forums for existing discussion
threads so far is limited to keyword-based search due
to the minimal effort required on part of the users. However,
it is often not possible to capture all the relevant context in a
complex query using a small number of keywords. Examplebased
search that retrieves similar discussion threads given
one exemplary thread is an alternate approach that can help
the user provide richer context and vastly improve forum
search results. In this paper, we address the problem of
finding similar threads to a given thread. Towards this, we
propose a novel methodology to estimate similarity between
discussion threads. Our method exploits the thread structure
to decompose threads in to set of weighted overlapping
components. It then estimates pairwise thread similarities
by quantifying how well the information in the threads are
mutually contained within each other using lexical similarities
between their underlying components. We compare our
proposed methods on real datasets against state-of-the-art
thread retrieval mechanisms wherein we illustrate that our
techniques outperform others by large margins on popular
retrieval evaluation measures such as NDCG, MAP, Precision@k
and MRR. In particular, consistent improvements of
up to 10% are observed on all evaluation measures

A inferência lexical entre as estratégias de compreensão escrita em alunos portugueses de espanhol língua estrangeira

Relatório da prática de ensino supervisionada, Mestrado em Ensino do Espanhol Língua Estrangeira, Universidade de Lisboa, 2011

Entangled semantics

In the context of monolingual and bilingual retrieval, Simple Knowledge Organisation System (SKOS) datasets can play a dual role as knowledge bases for semantic annotations and as language-independent resources for translation. With no existing track of formal evaluations of these aspects for datasets in SKOS format, we describe a case study on the usage of the Thesaurus for the Social Sciences in SKOS format for a retrieval setup based on the CLEF 2004-2006 Domain-Specific Track topics, documents and relevance assessments. Results showed a mixed picture with significant system-level improvements in terms of mean average precision in the bilingual runs. Our experiments set a new and improved baseline for using SKOS-based datasets with the GIRT collection and are an example of component-based evaluation.

Cappadocia: where Greek prepositions come to die

The Cappadocian variety of Ulaghátsh is unique among the Greek-speaking world in having lost the inherited preposition ‘se’. The innovation is found with both locative and allative uses and has af-ected both syntactic contexts in which ‘se’ was originally found, that is, as a simple preposition (1) and as the left-occurring member of circumpositions of the type ‘se’ + NP + spatial adverb (2). (1) a. tránse ci [to meidán] en ávʝa see.PST.3SG COMP ART.DEF.SG.ACC yard.SG.ACC COP.3 game.PL.NOM ‘he saw that in the yard is some game’ (Dawkins 1916: 348) b. ta erʝó da qardáʃa évɣan [to qonáq] ART.DEF.PL.NOM two ART.DEF.PL.NOM friend.PL.NOM ascend.PST.3PL ART.DEF.SG.ACC house.SG.ACC ‘the two friends went up to the house’ (Dawkins 1916: 354) (2) émi [ta qonáca mésa], kiríʃde [to ʝasdɯ́q píso] enter.PST.3SG ART.DEF.PL.NOM house.PL.ACC inside hide.PST.3SG. ART.DEF.SG.ACC cushion.SG.ACC behind ‘he went into the houses and hid behind the cushions’ (Dawkins 1916: 348) In this paper, we set out to provide (a) a diachronic account of the loss of ‘se’ in Asia Minor Greek, and (b) a synchronic analysis of its ramifications for the encoding of the semantic and grammatical functions it had prior to its loss. The diachronic development of ‘se’ is traced by comparing the Ulaghátsh data with those obtained from Cappadocian varieties that have neither lost it nor do they show signs of losing it and, crucially, also from varieties in which ‘se’ is in the process of being lost. The comparative analysis shows that the loss first became manifest in circumpositions in which ‘se’ was preposed to the complement to which in turn a wide range of adverbs expressing topological relations were postposed (émi sa qonáca mésa > émi ta qonáca mésa). This finding is accounted for in terms of Sinha and Kuteva’s (1995) distributed spatial semantics framework, which accepts that the elements involved in the constructions under investigation—the verb (émi), ‘se’ and the spatial adverb (mésa)—all contribute to the expression of the spatial relational meaning but with differences in weighting. Of the three, ‘eis’ made the most minimal contribution, the bulk of it being distributed over the verb and the adverb. This allowed for it to be optionally dropped from circumpositions, a stage attested in Phlo-tá Cappadocian and Silliot, and to be later completely abandoned, originally in allative and subsequently in locative contexts (earlier: évɣan so qonáq > évɣan to qonáq; later: so meidán en ávʝa > to meidán en ávʝa). The earlier loss in allative contexts is also dealt with in distributed semantics terms as verbs of motion such as έβγαν are semantically more loaded than vacuous verbs like the copula and therefore the preposition could be left out in the former context more easily than in the latter. The analysis also addresses the possibility that the loss of ‘se’ may ultimately originate in substandard forms of Medieval Greek, which according to Tachibana (1994) displayed SPATIAL ADVERB + NP constructions. Applying the semantic map model (Croft 2003, Haspelmath 2003), the synchronic analysis of the varieties that retain ‘se’ reveals that—like many other allative markers crosslinguistically—it displays a pattern of multifunctionality in expressing nine different functions (among others allative, locative, recipient, addressee, experiencer), which can be mapped against four domains, viz. the spatiotemporal, the social, the mental and the logicotextual (cf. Rice & Kabata 2007). In Ulaghátsh Cappadocian, none of these functions is overtly marked as such. In cases like (1), the intended spatial relational meaning is arrived at through the combination of the syntax and the inherent semantics of the verb and the zero-marked NP as well as from the context. In environments of the type exemplified by (2), the adverb contributes further to the correct interpretation. The analysis additionally shows that, despite the loss of ‘se’, Ulaghátsh patterns with all other Cappadocian varieties in one important aspect: Goal and Location are expressed similarly (by zero in Ulaghátsh, by ‘se’ in the other varieties) whereas Source is being kept distinct (expressed by ‘apó’ in all varieties). Goal-Location polysemy is very common across the world’s languages and, most crucially, prevails over other possible polysemies in the tripartite distinction Source—Location—Goal (Lestrade 2010, Nikitina 2009). Taking into account this empirical observation, our findings suggest that the reor-anisation of spatial systems can have a local effect—in our case the loss of a member of the prepositional paradigm—but will keep the original global picture intact, thus conforming to crosslinguistically robust tendencies.  References Croft, W. 2001. Radical Construction Grammar: Syntactic Theory in Typological Perspective. Oxford: Oxford University Press. Dawkins, R. M. 1916. Modern Greek in Asia Minor: A Study of the Dialects of Sílli, Cappadocia and Phárasa with Grammar, Texts, Translations and Glossary. Cambridge: Cambridge University Press. Haspelmath, M. 2003. The geometry of grammatical meaning: semantic maps and cross-linguistic comparison. In M. Tomasello (Ed.), The New Psychology of Language, Volume 2. New York: Erlbaum, 211–243. Lestrade, S. 2010. The Space of Case. Doctoral dissertation. Radboud University Nijmegen. Nikitina, T. 2009. Subcategorization pattern and lexical meaning of motion verbs: a study of the source/goal ambiguity. Linguistics 47, 1113–1141. Rice, S. & K. Kabata. 2007. Cross-linguistic grammaticalization patterns of the allative. Linguistic Typology 11, 451–514. Sinha, C. & T. Kuteva. 1995. Distributed spatial semantics. Nordic Journal of Linguistics 18:2, 167–199. Tachibana, T. 1994. Syntactic structure of spatial expressions in the “Late Byzantine Prose Alexander Romance”. Propylaia 6, 35–51.

Desenvolvimento lexical: perspectivas e práticas de professores no 1.º ciclo do ensino básico

Dissertação apresentada à Escola Superior de Educação de Lisboa para a obtenção de grau de Mestre em Didática da Língua Portuguesa no 1.º e 2.º Ciclos do Ensino Básico

Semantics of logic programs with explicit negation

After a historical introduction, the bulk of the thesis concerns the study of a declarative semantics for logic programs. The main original contributions are: ² WFSX (Well–Founded Semantics with eXplicit negation), a new semantics for logic programs with explicit negation (i.e. extended logic programs), which compares favourably in its properties with other extant semantics. ² A generic characterization schema that facilitates comparisons among a diversity of semantics of extended logic programs, including WFSX. ² An autoepistemic and a default logic corresponding to WFSX, which solve existing problems of the classical approaches to autoepistemic and default logics, and clarify the meaning of explicit negation in logic programs. ² A framework for defining a spectrum of semantics of extended logic programs based on the abduction of negative hypotheses. This framework allows for the characterization of different levels of scepticism/credulity, consensuality, and argumentation. One of the semantics of abduction coincides with WFSX. ² O–semantics, a semantics that uniquely adds more CWA hypotheses to WFSX. The techniques used for doing so are applicable as well to the well–founded semantics of normal logic programs. ² By introducing explicit negation into logic programs contradiction may appear. I present two approaches for dealing with contradiction, and show their equivalence. One of the approaches consists in avoiding contradiction, and is based on restrictions in the adoption of abductive hypotheses. The other approach consists in removing contradiction, and is based in a transformation of contradictory programs into noncontradictory ones, guided by the reasons for contradiction.