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 Grammars & Parsing


Unsupervised Semantic Action Discovery from Video Collections

arXiv.org Machine Learning

Human communication takes many forms, including speech, text and instructional videos. It typically has an underlying structure, with a starting point, ending, and certain objective steps between them. In this paper, we consider instructional videos where there are tens of millions of them on the Internet. We propose a method for parsing a video into such semantic steps in an unsupervised way. Our method is capable of providing a semantic "storyline" of the video composed of its objective steps. We accomplish this using both visual and language cues in a joint generative model. Our method can also provide a textual description for each of the identified semantic steps and video segments. We evaluate our method on a large number of complex YouTube videos and show that our method discovers semantically correct instructions for a variety of tasks.


Validity

#artificialintelligence

A lot of discussion around Matt Jockers' Syuzhet package (involving Annie Swafford, Ted Underwood, Andrew Piper, Scott Weingart and many others) has focused on issues of validity -- whether sentiment analysis is accurate enough for the task, whether the Fourier transform is an appropriate method for dimensionality reduction, whether the emotional trajectories themselves are valid measurements of anything at all (Scott has a good enumeration of the various issues here.) Andrew's discussion of the validity of inherently subjective measurements inspired me to solicit at least one data point from readers that we can use for one question under discussion with Syuzhet: what does a human judgment of the "emotional trajectory" of a work look like, and how often do readers agree with each other on this task? This method of soliciting human judgments for inherently subjective tasks is at the core of NLP and a lot of machine learning -- syntactic parsing, part of speech tagging, named entity recognition, topic classification, sentiment analysis, and lots of other tasks all rely on humans making judgments that are often surprisingly difficult in practice; learning algorithms in these cases are not so much learning any notion of "truth" but simply to reproduce the human judgments they're given. Agreement rates between humans is often seen as a proxy for the complexity of the task; if humans can't agree, it can be a sign that the task is ill-defined or underspecified. Word sense disambiguation is one good example of this, with low inter-annotator agreement rates [Snyder and Palmer 2004]; while sentiment analysis was originally designed with product/movie reviews in mind (does person X like product Y?) -- i.e., attitude with respect to a particular target -- I think the more general sentiment-as-tone problem (is this tweet happy or sad?) is much less well specified as a problem with an answer that can be judged by anyone but the original author. One aspect of those kind of annotations that I think is much less explored (which Piper points to and I think would be an extremely interesting area to work on) is the case where multiple judgments are simultaneously valid -- different interpretations of the same phenomenon, each backed by their own argument.


Text Analysis blog Aylien

#artificialintelligence

As you may know we recently launched a new service offering, our News API, and over the past week or so we've been using it to run some little experiments around analyzing news content. We wanted to use the News API to collect and analyze popular news headlines. We set out to find both similarities and differences in the way two journalists write headlines for their respective news articles and blog posts. Note: For a more technical, in-depth and interactive representation of this project, check out the Jupyter notebook we created. This includes sample code and more in depth descriptions of our approach.


A Distributed Representation-Based Framework for Cross-Lingual Transfer Parsing

Journal of Artificial Intelligence Research

This paper investigates the problem of cross-lingual transfer parsing, aiming at inducing dependency parsers for low-resource languages while using only training data from a resource-rich language (e.g., English). Existing model transfer approaches typically don't include lexical features, which are not transferable across languages. In this paper, we bridge the lexical feature gap by using distributed feature representations and their composition. We provide two algorithms for inducing cross-lingual distributed representations of words, which map vocabularies from two different languages into a common vector space. Consequently, both lexical features and non-lexical features can be used in our model for cross-lingual transfer. Furthermore, our framework is flexible enough to incorporate additional useful features such as cross-lingual word clusters. Our combined contributions achieve an average relative error reduction of 10.9% in labeled attachment score as compared with the delexicalized parser, trained on English universal treebank and transferred to three other languages. It also significantly outperforms state-of-the-art delexicalized models augmented with projected cluster features on identical data. Finally, we demonstrate that our models can be further boosted with minimal supervision (e.g., 100 annotated sentences) from target languages, which is of great significance for practical usage.


Collection of Machine Learning Interview Questions

#artificialintelligence

Here is the link to coursera course for NLP Pick the software from the The Stanford NLP (Natural Language Processing) Group and input some text to view its parse tree, named entities, part of speech tags, etc.


Joint Inference over a Lightly Supervised Information Extraction Pipeline: Towards Event Coreference Resolution for Resource-Scarce Languages

AAAI Conferences

We address two key challenges in end-to-end event coreference resolution research: (1) the error propagation problem, where an event coreference resolver has to assume as input the noisy outputs produced by its upstream components in the standard information extraction (IE) pipeline; and (2) the data annotation bottleneck, where manually annotating data for all the components in the IE pipeline is prohibitively expensive. This is the case in the vast majority of the world's natural languages, where such annotated resources are not readily available. To address these problems, we propose to perform joint inference over a lightly supervised IE pipeline, where all the models are trained using either active learning or unsupervised learning. Using our approach, only 25% of the training sentences in the Chinese portion of the ACE 2005 corpus need to be annotated with entity and event mentions in order for our event coreference resolver to surpass its fully supervised counterpart in performance.


Inferring Interpersonal Relations in Narrative Summaries

AAAI Conferences

Characterizing relationships between people is fundamental for the understanding of narratives. In this work, we address the problem of inferring the polarity of relationships between people in narrative summaries. We formulate the problem as a joint structured prediction for each narrative, and present a general model that combines evidence from linguistic and semantic features, as well as features based on the structure of the social community in the text. We additionally provide a clustering-based approach that can exploit regularities in narrative types. e.g., learn an affinity for love-triangles in romantic stories. On a dataset of movie summaries from Wikipedia, our structured models provide more than 30% error-reduction over a competitive baseline that considers pairs of characters in isolation.


Pose-Guided Human Parsing by an AND/OR Graph Using Pose-Context Features

AAAI Conferences

Parsing human into semantic parts is crucial to human-centric analysis. In this paper, we propose a human parsing pipeline that uses pose cues, i.e., estimates of human joint locations, to provide pose-guided segment proposals for semantic parts. These segment proposals are ranked using standard appearance cues, deep-learned semantic feature, and a novel pose feature called pose-context. Then these proposals are selected and assembled using an And-Or graph to output a parse of the person. The And-Or graph is able to deal with large human appearance variability due to pose, choice of clothes, etc. We evaluate our approach on the popular Penn-Fudan pedestrian parsing dataset, showing that it significantly outperforms the state-of-the-arts, and perform diagnostics to demonstrate the effectiveness of different stages of our pipeline.


A Joint Model for Question Answering over Multiple Knowledge Bases

AAAI Conferences

As the amount of knowledge bases (KBs) grows rapidly, the problem of question answering (QA) over multiple KBs has drawn more attention. The most significant distinction between multiple KB-QA and single KB-QA is that the former must consider the alignments between KBs. The pipeline strategy first constructs the alignments independently, and then uses the obtained alignments to construct queries. However, alignment construction is not a trivial task, and the introduced noises would be passed on to query construction. By contrast, we notice that alignment construction and query construction are interactive steps, and jointly considering them would be beneficial. To this end, we present a novel joint model based on integer linear programming (ILP), uniting these two procedures into a uniform framework. The experimental results demonstrate that the proposed approach outperforms state-of-the-art systems, and is able to improve the performance of both alignment construction and query construction.


Joint Word Segmentation, POS-Tagging and Syntactic Chunking

AAAI Conferences

Chinese chunking has traditionally been solved by assuming gold standard word segmentation.We find that the accuracies drop drastically when automatic segmentation is used.Inspired by the fact that chunking knowledge can potentially improve segmentation, we explore a joint model that performs segmentation, POS-tagging and chunking simultaneously.In addition, to address the sparsity of full chunk features, we employ a semi-supervised method to derive chunk cluster features from large-scale automatically-chunked data.Results show the effectiveness of the joint model with semi-supervised features.