Automatically classifying non-functional requirements using deep neural network

Abstract

Non-functional requirements are property that software products must have in order to meet the user’s business requirements, and are additional constraints on the quality and characteristics of software systems. They are generally written by software designers and documented in various parts of requirements documentation. When developing systems, developers need to classify non-functional requirements from requirements documents, and classifying these non-functional requirements requires professional skills, experience, and domain knowledge, which is challenging and time-consuming for developers. It would be beneficial to implement automatic classification of non-functional requirements from requirements documents, which could reduce the manual, time, and mental fatigue involved in identifying specific non-functional requirements from a large number of requirements. In this paper, a deep neural network model called NFRNet is designed to automatically classify non-functional requirements from software requirement documents. The network consists of two parts. One is an improved BERT word embedding model based on N-gram masking for learning context representation of the requirement descriptions, and the other is a Bi-LSTM classification network for capture context information of the requirement descriptions. We use a Softmax classifier in the end to classify the requirement descriptions. At the same time, in order to accelerate the training and improve the generalization ability of the model, the network uses multi-sample dropout regularization technology. This new regularization technology can reduce the number of iterations needed for training, accelerate the training of deep neural networks, and the networks trained achieved lower error rates. In addition, we expanded the original non-functional requirements dataset (PROMISE dataset) and designed a new dataset called SOFTWARE NFR. The new dataset far exceeds the original dataset in terms of the number of requirement description sentences and the number of non-functional requirements categories. It can be taken as a new testbed for non-functional requirements classification. Through cross-validation on the new dataset, the experimental results show that the network designed in this paper is significantly better than the other 17 classification methods in terms of Precision, Recall, and F1-score. At the same time, for the training set and the validation set, using the multi-sample dropout regularization technology can accelerate the training speed, reduce the number of iterations, and achieve lower error rates and loss.