Table 2.

Customer service based Chatbot approaches with various attributes

Approach refs.	Year	Approach	Language processing technique	Type of customers	Knowledge source
[65]	2016	• Apache PDFBOX to extract text from PDF	AIML	Open ended	• PDF
		• Over generating transformations and ranking algorithm to generate questions			• Digital photos
		• Pattern matching
[11]	2017	• If This Then That (IFTTT) approach for mail and SMS alerts	NLTK	Open ended	• Data collected by queries asked to the user
		• keywords and actions matching
[49]	2017	• Artificial intelligence	JavaScript object notation (JASON)	Patients	• Conversational data of chatbot
		• Matching keywords and symptoms			• Medical enquiry data
		• Clustering			• Symptoms data
		Medical Predictions System
[74]	2017	• Long short-term memory (LSTM) Recurrent neural network (RNN)	Word segmentation tool—Jieba	Closed domain-elders	• MHMC chitchat dataset
		• GloVe method to train word vector model			• Chinese gigaword corpus
		• Euclidean distance to select a proper question-response pair
[1]	2017	Text matching	• Chatterbox and	Open ended	• No specific knowledge base
			• NLP toolkit		• Used WWW for response
[45]	2017	• Bag of words method	NLTK	Bank users	FAQ from different banking platforms
		• Query and answer mapping using cosine similarity
[62]	2018	• Question generation model	• Dependency parser	Children	• Approximately one hundred articles from the website, http://www.yfes.tn.edu.tw/yfesvi/story.htm
		• Question ranking model	• Part-of-speech tagger tool
		• Logistic regression
		• Supervised learning
[66]	2018	Pattern matching	• AIML and	University	• FAQ dataset
			• LSA	College
[72]	2018	• Web hook to deliver the user query to the server	Facebook messenger API	College students	Own database which stores all the information about questions, answers, keywords, logs and feedback messages
		• Pre-trained artificial intelligence module WIT.AI to answer the user’s query with efficiency and accuracy
[61]	2018	• Thesaurus generation function using ML	JASON, XML	Financial domain	FAQ of Call centre response manual, business manual etc. and data of office document
		• Script editing function—to construct as per convenience
[64]	2019	• Intelligent social therapeutic chatbot	• Punkt sentence Tokenizer	Stressed	• ISEAR dataset
		• Neural network embedding’s	• Global Vectors for Word Representation (GloVe)	Students	• Users’ chat data
		• Distribution of text into emotion labels
		• Deep learning classifiers—CNN, RNN, and HAN
[2]	2020	Add-on to the telegram to share the disaster information	Telegram API	Foreigners trapped in disaster-affected areas	• Google maps
					• Weather API of open weather
					• Government web site of Japan
					• Shared pictures by users
[39]	2020	ML	• Tokenization using TF-IDF vector cosign algorithm	Bank users	Entire article from banksofmumbai.in
			• Lemmatization
			• Vectorization
[90]	2021	• Bayesian deep learning	BERT	Financial domain	Interaction logs of phone agents and the expert team
		• MCD method