Question: In which terms does the MetaLDA achieve improved performance?
Evidence: With the rapid growth of the internet, huge amounts of text data are generated in social networks, online shopping and news websites, etc. These data create demand for powerful and efficient text analysis techniques. Probabilistic topic models such as Latent Dirichlet Allocation (LDA) BIBREF0 are popular approaches for this task, by discovering latent topics from text collections. Many conventional topic models discover topics purely based on the word-occurrences, ignoring the meta information (a.k.a., side information) associated with the content. In contrast, when we humans read text it is natural to leverage meta information to improve our comprehension, which includes categories, authors, timestamps, the semantic meanings of the words, etc. Therefore, topic models capable of using meta information should yield improved modelling accuracy and topic quality.
In practice, various kinds of meta information are available at the document level and the word level in many corpora. At the document level, labels of documents can be used to guide topic learning so that more meaningful topics can be discovered. Moreover, it is highly likely that documents with common labels discuss similar topics, which could further result in similar topic distributions. For example, if we use authors as labels for scientific papers, the topics of the papers published by the same researcher can be closely related.
At the word level, different semantic/syntactic features are also accessible. For example, there are features regarding word relationships, such as synonyms obtained from WordNet BIBREF1 , word co-occurrence patterns obtained from a large corpus, and linked concepts from knowledge graphs. It is preferable that words having similar meaning but different morphological forms, like “dog” and “puppy”, are assigned to the same topic, even if they barely co-occur in the modelled corpus. Recently, word embeddings generated by GloVe BIBREF2 and word2vec BIBREF3 , have attracted a lot of attention in natural language processing and related fields. It has been shown that the word embeddings can capture both the semantic and syntactic features of words so that similar words are close to each other in the embedding space. It seems reasonable to expect that these word embedding will improve topic modelling BIBREF4 , BIBREF5 .
Conventional topic models can suffer from a large performance degradation over short texts (e.g., tweets and news headlines) because of insufficient word co-occurrence information. In such cases, meta information of documents and words can play an important role in analysing short texts by compensating the lost information in word co-occurrences. At the document level, for example, tweets are usually associated with hashtags, users, locations, and timestamps, which can be used to alleviate the data sparsity problem. At the word level, word semantic similarity and embeddings obtained or trained on large external corpus (e.g., Google News or Wikipedia) have been proven useful in learning meaningful topics from short texts BIBREF6 , BIBREF7 .
The benefit of using document and word meta information separately is shown in several models such as BIBREF8 , BIBREF9 , BIBREF5 . However, in existing models this is usually not efficient enough due to non-conjugacy and/or complex model structures. Moreover, only one kind of meta information (either at document level or at word level) is used in most existing models. In this paper, we propose MetaLDA, a topic model that can effectively and efficiently leverage arbitrary document and word meta information encoded in binary form. Specifically, the labels of a document in MetaLDA are incorporated in the prior of the per-document topic distributions. If two documents have similar labels, their topic distributions should be generated with similar Dirichlet priors. Analogously, at the word level, the features of a word are incorporated in the prior of the per-topic word distributions, which encourages words with similar features to have similar weights across topics. Therefore, both document and word meta information, if and when they are available, can be flexibly and simultaneously incorporated using MetaLDA. MetaLDA has the following key properties:
We conduct extensive experiments with several real datasets including regular and short texts in various domains. The experimental results demonstrate that MetaLDA achieves improved performance in terms of perplexity, topic coherence, and running time.
The experimental results demonstrate that MetaLDA achieves improved performance in terms of perplexity, topic coherence, and running time.
Answer: The experimental results demonstrate that MetaLDA achieves improved performance in terms of perplexity, topic coherence, and running time.