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Leveraging Web Semantic Knowledge in Word Representation Learning The Thirty-Third AAAI Conference on Artificial Intelligence (AAAI-19) Leveraging Web Semantic Knowledge in Word Representation Learning Haoyan Liu,1∗ Lei Fang,2 Jian-Guang Lou,2 Zhoujun Li1 1State Key Lab of Software Development Environment, Beihang University, Beijing, China 2Microsoft Research, Beijing, China fhaoyan.liu, [email protected]; fleifa, [email protected] Abstract manually created, semantic lexicons or linguistic structures. 1 Much recent work focuses on leveraging semantic lexi- Even for high-quality semantic resources like WordNet , the cons like WordNet to enhance word representation learning coverage might be quite limited. Taking English WordNet as (WRL) and achieves promising performance on many NLP an example, it only contains 155K words organized in 176K tasks. However, most existing methods might have limitations synsets, which is rather small compared to the large vocabu- because they require high-quality, manually created, semantic lary size on the training data. Vulic´ et al. (2018) and Glavasˇ lexicons or linguistic structures. In this paper, we propose to and Vulic´ (2018) partially solve this problem by first design- leverage semantic knowledge automatically mined from web ing a mapping function that learns the specialization process structured data to enhance WRL. We first construct a seman- for seen words, and then applying the learned function to tic similarity graph, which is referred as semantic knowledge, unseen words in semantic lexicons. Unfortunately, their ap- based on a large collection of semantic lists extracted from proaches still depend on the linguistic constraints derived the web using several pre-defined HTML tag patterns. Then we introduce an efficient joint word representation learning from manually created resources. Therefore, we shall lever- model to capture semantics from both semantic knowledge age semantic resources that can be automatically constructed and text corpora. Compared with recent work on improving with a relatively high coverage on the vocabulary. WRL with semantic resources, our approach is more general, and can be easily scaled with no additional effort. Extensive experimental results show that our approach outperforms the state-of-the-art methods on word similarity, word sense dis- ambiguation, text classification and textual similarity tasks. 1 Introduction Distributed word representations boost performance of many NLP applications mainly because they are capable of capturing semantic regularities from a collection of text se- quences. Much research work tries to enhance word repre- Figure 1: News categories with HTML structures.2 sentation learning (WRL) from the semantic perspective by leveraging semantic lexicons. Semantic lexicons can be con- There is a considerable amount of structured data on the sidered as a collection of lists, in which each list consists web, such as tables, select options, drop down lists, etc. of semantically related words. Some existing work pulls Given a web table, entries in the same column or row are the vectors of synonyms close by either a post-processing usually highly semantically related. This inspires the idea model (Faruqui et al. 2015) or a joint representation learn- that it is promising to automatically construct the semantic ing model with the distances between synonyms as regular- resources based on those semantically related entries. Fig- izers (Kiela, Hill, and Clark 2015; Bollegala et al. 2016). ure 1 shows an example of news categories with their cor- More recently, many manually well-designed semantic rela- responding HTML structures. It can be seen that Politics, tions or linguist structures, such as synonyms and antonyms Entertainment, Health are semantically related, because all (Mrksiˇ c´ et al. 2017; Glavasˇ and Vulic´ 2018), concept con- of them can be treated as news categories. In the HTML vergence and word divergence (Liu et al. 2018), have been DOM tree, Politics, Entertainment, Health share the same used to enhance the semantics of words. HTML structure, which means that they can be easily ex- However, it should be noted that most existing models tracted using HTML tag patterns. Moreover, we find that se- might have limitations because they require high-quality, mantic information in structured data could be an enhance- ∗This work was done when the first author was an intern at Mi- ment or complement for text corpora. Consider the entries crosoft Research Asia. Copyright c 2019, Association for the Advancement of Artificial 1https://wordnet.princeton.edu/ Intelligence (www.aaai.org). All rights reserved. 2The categories are from https://abcnews.go.com/. 6746 in news categories again, in text sequences, they hardly ap- al. (2017) exploit morphological synonyms to pull the in- pear with similar contexts, but they might frequently appear flectional forms of the same word closer together and push in the navigation bars on news websites. derivational antonyms further apart. Therefore, we propose to use some pre-defined HTML tag Joint learning models. Many joint learning models intro- patterns to extract semantic lists from web data in a large duce semantic lexicons or linguistic structures as additional scale. However, the extracted semantic lists cannot be di- constraints to the representation learning models (Liu et al. rectly used by existing methods, because they contain much 2015; Ono, Miwa, and Sasaki 2015; Nguyen et al. 2017). noise, and some of the lists are highly redundant. To address Yu and Dredze (2014) integrate word2vec (Mikolov et al. this issue, we design a similarity function that measures the 2013) with synonym constraints that the distances between semantic relatedness between each co-occurred word pair. synonym representations shall be close. Liu et al. (2018) After that, we build a semantic similarity graph, in which introduce the semantic constraints of concept convergence words are represented as vertices and each edge indicates and word divergence derived from hypernym-hyponym re- the similarity score between the corresponding two vertices. lations in WordNet to word2vec. Bollegala et al. (2016) ex- This semantic similarity graph is considered as web seman- tend GloVe (Pennington, Socher, and Manning 2014) by tic knowledge to further enhance WRL. adding constraints of various semantic relationships such as In this paper, we propose WESEK, Word Embedding synonyms, antonyms, hypernyms and hyponyms. Osborne, with web SEmantic Knowledge, to capture semantics from Narayan, and Cohen (2016) propose to find a projection both the text and web semantic knowledge. The intuition of the two views (word embeddings and semantic knowl- behind WESEK is that, given two words, the similarity of edge) in a shared space such that the correlation between the learned representations shall be high if they are connected two views is maximized with minimal redundancy. For other in the semantic similarity graph. Our major contributions joint learning models, Kiela, Hill, and Clark (2015) treat se- are: 1) we build high-quality semantic knowledge from web mantically related words as alternative contexts by adding structured data, which can be easily scaled with no addi- them to the original context window in text corpora; Niu et tional human effort; 2) we propose a novel joint represen- al. (2017) utilize word sememes, which are the minimum tation learning model that is capable of capturing semantics semantic units of word meanings, to improve WRL with an from both the text and semantic knowledge. Experimental attention scheme. results show that WESEK outperforms state-of-the-art word embeddings on multiple popular NLP tasks like word sim- 2.2 Semantic Knowledge Construction ilarity, word sense disambiguation, text classifications and Both post-processing and joint learning models require textual similarity, which demonstrate that leveraging web se- high-quality, manually constructed, semantic lexicons or lin- mantic knowledge improves WRL and that WESEK is capa- guistic structures (Nguyen et al. 2017; Liu et al. 2018; ble of encoding web semantic knowledge effectively. Mrksiˇ c´ et al. 2016; Glavasˇ and Vulic´ 2018). It should be noted that structured data on the web contains rich semantic 2 Related Work information, which has the advantage that it can be easily extracted (Zhang et al. 2013). There is much related work Our work is related to 1) word representation specialization on mining semantic knowledge automatically from web data or retrofitting using semantic lexicons or linguistic struc- (Pasca 2004; Zhang et al. 2009; Shi et al. 2010; Wu et al. tures, and 2) semantic knowledge construction from the web. 2012); which generally uses Hearst patterns (Hearst 1992) to discover coordinative words in the text, and HTML tag 2.1 Word Representation Specialization patterns to extract words sharing the same HTML struc- Most specialization models make use of external resources ture. Shi et al. (2010) propose using both textual context like WordNet or the Paraphrase Database3 (PPDB) to derive and HTML tag patterns to extract semantic lists from web semantic lexicons or linguistic structures. Generally, they data; and Zhang et al. (2009) utilize topic models to try to fall into two categories: post-processing and joint learning. obtain high-quality semantic classes from raw semantic lists Post-processing models. The inputs of post-processing extracted from the web. In this paper, we first extract a large models are pre-trained word embeddings, which means collection of semantic lists with several pre-defined HTML that
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