73 research outputs found
Ontology: Towards a new synthesis
This introduction to the second international conference on Formal Ontology and
Information Systems presents a brief history of ontology as a discipline spanning the boundaries of philosophy and information science. We sketch some of the reasons for the growth of ontology in the information science field, and offer a preliminary stocktaking of how the term ‘ontology’ is currently used. We conclude by suggesting some grounds for optimism as concerns the future collaboration between philosophical ontologists and information scientists
Capturing Ambiguity in Crowdsourcing Frame Disambiguation
FrameNet is a computational linguistics resource composed of semantic frames,
high-level concepts that represent the meanings of words. In this paper, we
present an approach to gather frame disambiguation annotations in sentences
using a crowdsourcing approach with multiple workers per sentence to capture
inter-annotator disagreement. We perform an experiment over a set of 433
sentences annotated with frames from the FrameNet corpus, and show that the
aggregated crowd annotations achieve an F1 score greater than 0.67 as compared
to expert linguists. We highlight cases where the crowd annotation was correct
even though the expert is in disagreement, arguing for the need to have
multiple annotators per sentence. Most importantly, we examine cases in which
crowd workers could not agree, and demonstrate that these cases exhibit
ambiguity, either in the sentence, frame, or the task itself, and argue that
collapsing such cases to a single, discrete truth value (i.e. correct or
incorrect) is inappropriate, creating arbitrary targets for machine learning.Comment: in publication at the sixth AAAI Conference on Human Computation and
Crowdsourcing (HCOMP) 201
A Crowdsourced Frame Disambiguation Corpus with Ambiguity
We present a resource for the task of FrameNet semantic frame disambiguation
of over 5,000 word-sentence pairs from the Wikipedia corpus. The annotations
were collected using a novel crowdsourcing approach with multiple workers per
sentence to capture inter-annotator disagreement. In contrast to the typical
approach of attributing the best single frame to each word, we provide a list
of frames with disagreement-based scores that express the confidence with which
each frame applies to the word. This is based on the idea that inter-annotator
disagreement is at least partly caused by ambiguity that is inherent to the
text and frames. We have found many examples where the semantics of individual
frames overlap sufficiently to make them acceptable alternatives for
interpreting a sentence. We have argued that ignoring this ambiguity creates an
overly arbitrary target for training and evaluating natural language processing
systems - if humans cannot agree, why would we expect the correct answer from a
machine to be any different? To process this data we also utilized an expanded
lemma-set provided by the Framester system, which merges FN with WordNet to
enhance coverage. Our dataset includes annotations of 1,000 sentence-word pairs
whose lemmas are not part of FN. Finally we present metrics for evaluating
frame disambiguation systems that account for ambiguity.Comment: Accepted to NAACL-HLT201
Crowdsourcing Semantic Label Propagation in Relation Classification
Distant supervision is a popular method for performing relation extraction
from text that is known to produce noisy labels. Most progress in relation
extraction and classification has been made with crowdsourced corrections to
distant-supervised labels, and there is evidence that indicates still more
would be better. In this paper, we explore the problem of propagating human
annotation signals gathered for open-domain relation classification through the
CrowdTruth methodology for crowdsourcing, that captures ambiguity in
annotations by measuring inter-annotator disagreement. Our approach propagates
annotations to sentences that are similar in a low dimensional embedding space,
expanding the number of labels by two orders of magnitude. Our experiments show
significant improvement in a sentence-level multi-class relation classifier.Comment: In publication at the First Workshop on Fact Extraction and
Verification (FeVer) at EMNLP 201
Truth Is a Lie: Crowd Truth and the Seven Myths of Human Annotation
Big data is having a disruptive impact across the sciences. Human annotation of semantic interpretation tasks is a critical part of big data semantics, but it is based on an antiquated ideal of a single correct truth that needs to be similarly disrupted. We expose seven myths about human annotation, most of which derive from that antiquated ideal of truth, and dispell these myths with examples from our research. We propose a new theory of truth, crowd truth, that is based on the intuition that human interpretation is subjective, and that measuring annotations on the same objects of interpretation (in our examples, sentences) across a crowd will provide a useful representation of their subjectivity and the range of reasonable interpretations
CrowdTruth 2.0: Quality Metrics for Crowdsourcing with Disagreement
Typically crowdsourcing-based approaches to gather annotated data use
inter-annotator agreement as a measure of quality. However, in many domains,
there is ambiguity in the data, as well as a multitude of perspectives of the
information examples. In this paper, we present ongoing work into the
CrowdTruth metrics, that capture and interpret inter-annotator disagreement in
crowdsourcing. The CrowdTruth metrics model the inter-dependency between the
three main components of a crowdsourcing system -- worker, input data, and
annotation. The goal of the metrics is to capture the degree of ambiguity in
each of these three components. The metrics are available online at
https://github.com/CrowdTruth/CrowdTruth-core
Empirical Methodology for Crowdsourcing Ground Truth
The process of gathering ground truth data through human annotation is a
major bottleneck in the use of information extraction methods for populating
the Semantic Web. Crowdsourcing-based approaches are gaining popularity in the
attempt to solve the issues related to volume of data and lack of annotators.
Typically these practices use inter-annotator agreement as a measure of
quality. However, in many domains, such as event detection, there is ambiguity
in the data, as well as a multitude of perspectives of the information
examples. We present an empirically derived methodology for efficiently
gathering of ground truth data in a diverse set of use cases covering a variety
of domains and annotation tasks. Central to our approach is the use of
CrowdTruth metrics that capture inter-annotator disagreement. We show that
measuring disagreement is essential for acquiring a high quality ground truth.
We achieve this by comparing the quality of the data aggregated with CrowdTruth
metrics with majority vote, over a set of diverse crowdsourcing tasks: Medical
Relation Extraction, Twitter Event Identification, News Event Extraction and
Sound Interpretation. We also show that an increased number of crowd workers
leads to growth and stabilization in the quality of annotations, going against
the usual practice of employing a small number of annotators.Comment: in publication at the Semantic Web Journa
Hybrid Refining Approach of PrOnto Ontology
This paper presents a refinement of PrOnto ontology using a validation test based on legal experts’ annotation of privacy policies combined with an Open Knowledge Extraction (OKE) algorithm. To ensure robustness of the results while preserving an interdisciplinary approach, the integration of legal and technical knowledge has been carried out as follows. The set of privacy policies was first analysed by the legal experts to discover legal concepts and map the text into PrOnto. The mapping was then provided to computer scientists to perform the OKE analysis. Results were validated by the legal experts, who provided feedbacks and refinements (i.e. new classes and modules) of the ontology according to MeLOn methodology. Three iterations were performed on a set of (development) policies, and a final test using a new set of privacy policies. The results are 75,43% of detection of concepts in the policy texts and an increase of roughly 33% in the accuracy gain on the test set, using the new refined version of PrOnto enriched with SKOS-XL lexicon terms and definitions
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