Analysis Methods in Neural Language Processing: A Survey Transactions of the Association for Computational Linguistics MIT Press

Semantic Analysis in Natural Language Processing by Hemal Kithulagoda Voice Tech Podcast

This trend continues today, with research into modern architectures and what formal languages they can learn (Weiss et al., 2018; Bernardy, 2018; Suzgun et al., 2019), or the formal properties they possess (Chen et al., 2018b). Adversarial attacks can be classified to targeted vs. non-targeted attacks (Yuan et al., 2017). A targeted attack specifies a specific false class, l′, while a nontargeted attack cares only that the predicted class is wrong, l′ ≠ l. Targeted attacks are more difficult to generate, as they typically require knowledge of model parameters; that is, they are white-box attacks.

You can find out what a group of clustered words mean by doing principal component analysis (PCA) or dimensionality reduction with T-SNE, but this can sometimes be misleading because they oversimplify and leave a lot of information on the side. It’s a good way to get started (like logistic or linear regression in data science), but it isn’t cutting edge and it is possible to do it way better. The letters directly above the single words show the parts of speech for each word (noun, verb and determiner).

Advantages of Syntactic Analysis

However, explaining why a deep, highly non-linear neural network makes a certain prediction is not trivial. One solution is to ask the model to generate explanations along with its primary prediction (Zaidan et al., 2007; Zhang et al., 2016),15 but this approach requires manual annotations of explanations, which may be hard to collect. By far, the most targeted tasks in challenge sets are NLI and MT. This can partly be explained by the popularity of these tasks and the prevalence of neural models proposed for solving them.

You see, the word on its own matters less, and the words surrounding it matter more for the interpretation. A semantic analysis algorithm needs to be trained with a larger corpus of data to perform better. Zhao et al. (2018c) used generative adversarial networks (GANs) (Goodfellow et al., 2014) to minimize the distance between latent representations of input and adversarial examples, and performed perturbations in latent space. Since the latent representations do not need to come from the attacked model, this is a black-box attack. We note here also that judging the quality of a model by its performance on a challenge set can be tricky.

How is Semantic Analysis different from Lexical Analysis?

In machine translation done by deep learning algorithms, language is translated by starting with a sentence and generating vector representations that represent it. Then it starts to generate words in another language that entail the same information. With its ability to process large amounts of data, NLP can inform manufacturers on how to improve production workflows, when to perform machine maintenance and what issues need to be fixed in products. And if companies need to find the best price for specific materials, natural language processing can review various websites and locate the optimal price. Healthcare professionals can develop more efficient workflows with the help of natural language processing. During procedures, doctors can dictate their actions and notes to an app, which produces an accurate transcription.

• Semantic Analysis helps machines interpret the meaning of texts and extract useful information, thus providing invaluable data while reducing manual efforts.
• One could speculate that their decrease in popularity can be attributed to the rise of large-scale quantitative evaluation of statistical NLP systems.
• One solution is to ask the model to generate explanations along with its primary prediction (Zaidan et al., 2007; Zhang et al., 2016),15 but this approach requires manual annotations of explanations, which may be hard to collect.
• In addition, NLP’s data analysis capabilities are ideal for reviewing employee surveys and quickly determining how employees feel about the workplace.

Gathering market intelligence becomes much easier with natural language processing, which can analyze online reviews, social media posts and web forums. Compiling this data can help marketing teams understand what consumers care about and how they perceive a business’ brand. With sentiment analysis we want to determine the attitude (i.e. the sentiment) of a speaker or writer with respect to a document, interaction or event.

NLP has also been used for mining clinical documentation for cancer-related studies. This dataset is unique in its integration of existing semantic models from both the general and clinical NLP communities. This dataset has promoted the dissemination of adapted guidelines and the development of several open-source modules. However, manual annotation is time consuming, expensive, and labor intensive on the part of human annotators. Methods for creating annotated corpora more efficiently have been proposed in recent years, addressing efficiency issues such as affordability and scalability. NLP drives computer programs that translate text from one language to another, respond to spoken commands, and summarize large volumes of text rapidly—even in real time.

The first technique refers to text classification, while the second relates to text extractor. Relationship extraction is a procedure used to determine the semantic relationship between words in a text. In semantic analysis, relationships include various entities, such as an individual’s name, place, company, designation, etc.

Advantages of semantic analysis

Gulordava et al. (2018) extended this to other agreement phenomena, but they relied on syntactic information available in treebanks, resulting in a smaller dataset. Finally, the predictor for the auxiliary task is usually a simple classifier, such as logistic regression. A few studies compared different classifiers and found that deeper classifiers lead to overall better results, but do not alter the respective trends nlp semantic analysis when comparing different models or components (Qian et al., 2016b; Belinkov, 2018). Interestingly, Conneau et al. (2018) found that tasks requiring more nuanced linguistic knowledge (e.g., tree depth, coordination inversion) gain the most from using a deeper classifier. However, the approach is usually taken for granted; given its prevalence, it appears that better theoretical or empirical foundations are in place.

BoB applies the highest performing approaches from known de-identification systems for each PHI type, resulting in balanced recall and precision results (89%) for a configuration of individual classifiers, and best precision (95%) was obtained with a multi-class configuration. This system was also evaluated to understand the utility of texts by quantifying clinical information loss following PHI tagging i.e., medical concepts from the 2010 i2b2 Challenge corpus, in which less than 2% of the corpus concepts partially overlapped with the system [27]. Clinical NLP is the application of text processing approaches on documents written by healthcare professionals in clinical settings, such as notes and reports in health records. Clinical NLP can provide clinicians with critical patient case details, which are often locked within unstructured clinical texts and dispersed throughout a patient’s health record. Semantic analysis is one of the main goals of clinical NLP research and involves unlocking the meaning of these texts by identifying clinical entities (e.g., patients, clinicians) and events (e.g., diseases, treatments) and by representing relationships among them.

The values in 𝚺 represent how much each latent concept explains the variance in our data. When these are multiplied by the u column vector for that latent concept, it will effectively weigh that vector. The matrices 𝐴𝑖 are said to be separable because they can be decomposed into the outer product of two vectors, weighted by the singular value 𝝈i. Calculating the outer product of two vectors with shapes (m,) and (n,) would give us a matrix with a shape (m,n). In other words, every possible product of any two numbers in the two vectors is computed and placed in the new matrix. The singular value not only weights the sum but orders it, since the values are arranged in descending order, so that the first singular value is always the highest one.

More informative human studies evaluate grammaticality or similarity of the adversarial examples to the original ones (Zhao et al., 2018c; Alzantot et al., 2018). Given the inherent difficulty in generating imperceptible changes in text, more such evaluations are needed. Methods for generating targeted attacks in NLP could possibly take more inspiration from adversarial attacks in other fields. For instance, in attacking malware detection systems, several studies developed targeted attacks in a black-box scenario (Yuan et al., 2017).

Background – Identifying Existing Barriers and Recent Developments that Support Semantic Analysis

Much recent work has focused on visualizing activations on specific examples in modern neural networks for language (Karpathy et al., 2015; Kádár et al., 2017; Qian et al., 2016a; Liu et al., 2018) and speech (Wu and King, 2016; Nagamine et al., 2015; Wang et al., 2017b). Figure 1 shows an example visualization of a neuron that captures position of words in a sentence. The heatmap uses blue and red colors for negative and positive activation values, respectively, enabling the user to quickly grasp the function of this neuron. The semantic analysis method begins with a language-independent step of analyzing the set of words in the text to understand their meanings. This step is termed ‘lexical semantics‘ and refers to fetching the dictionary definition for the words in the text. Each element is designated a grammatical role, and the whole structure is processed to cut down on any confusion caused by ambiguous words having multiple meanings.

Often, semi-automatic methods are used to compile an initial list of examples that is manually verified by annotators. The specific method also affects the kind of language use and how natural or artificial/synthetic the examples are. We describe here some trends in dataset construction methods in the hope that they may be useful for researchers contemplating new datasets. Generally, datasets that are constructed programmatically tend to cover less fine-grained linguistic properties, while manually constructed datasets represent more diverse phenomena.

In the diagram below the geometric effect of M would be referred to as “shearing” the vector space; the two vectors 𝝈1 and 𝝈2 are actually our singular values plotted in this space. If we’re looking at foreign policy, we might see terms like “Middle East”, “EU”, “embassies”. For elections it might be “ballot”, “candidates”, “party”; and for reform we might see “bill”, “amendment” or “corruption”. So, if we plotted these topics and these terms in a different table, where the rows are the terms, we would see scores plotted for each term according to which topic it most strongly belonged. Suppose that we have some table of data, in this case text data, where each row is one document, and each column represents a term (which can be a word or a group of words, like “baker’s dozen” or “Downing Street”).

• As unfortunately usual in much NLP work, especially neural NLP, the vast majority of challenge sets are in English.
• It is a complex system, although little children can learn it pretty quickly.
• But before getting into the concept and approaches related to meaning representation, we need to understand the building blocks of semantic system.
• This approach resulted in an overall precision for all concept categories of 80% on a high-yield set of note titles.
• They conclude that it is not necessary to involve an entire document corpus for phenotyping using NLP, and that semantic attributes such as negation and context are the main source of false positives.