text: It is used in natural language processing and information retrieval (IR). It disregards grammar and word order but keeps multiplicity. The bag-of-words model has also been used for computer vision.The bag-of-words model is commonly used in methods of document classification where the (frequency of) occurrence of each word is used as a feature for training a classifier.An early reference to "bag of words" in a linguistic context can be found in Zellig Harris's 1954 article on Distributional Structure.The Bag-of-words model is one example of a Vector space model.