Requirement entities, "explicit specification of concepts that define the primary function objects", play an important role in requirement analysis for software development and maintenance. It is a labor-intensive activity to extract requirement entities from textual requirements, which is typically done manually. A few existing studies propose automated methods to support key requirement concept extraction. However, they face two main challenges: lack of domain-specific natural language processing techniques and expensive labeling effort. To address the challenges, this study presents a novel approach named RENE, which employs LSTM-CRF model for requirement entity extraction and introduces the general knowledge to reduce the demands for labeled data. It consists of four phases: 1) Model construction, where RENE builds LSTM-CRF model and an isomorphic LSTM language model for transfer learning; 2) LSTM language model training, where RENE captures general knowledge and adapt to requirement context; 3) LSTM-CRF training, where RENE trains the LSTM-CRF model with the transferred layers; 4) Requirement entity extraction, where RENE applies the trained LSTM-CRF model to a new-coming requirement, and automatically extracts its requirement entities. RENE is evaluated using two methods: evaluation on historical dataset and user study. The evaluation on the historical dataset shows that RENE could achieve 79% precision, 81% recall, and 80% F1. The evaluation results from the user study also suggest that RENE could produce more accurate and comprehensive requirement entities, compared with those produced by engineers.

In practice, it is very important to determine the size of a proposed software system yet to be built based on its requirements, i.e., early in the development life cycle. The most widely used approach for size estimation is Function Point Analysis (FPA). However, since FPA involves human judgment, the estimation results are some degree of subjective, and the process is labor and cost intensive. In this paper, we propose a novel approach to identify transaction functions from textual requirements automatically by leveraging a set of natural language processing techniques and machine learning models. We evaluate our approach on 1,864 requirements and 104,691 transaction functions taken from 36 financial projects from one banking industry. The results show that the contents of the suggested transaction functions by our approach are high in quality, with low perplexity value of 8.5 and high BLEU score of 34 on average. The types of suggested transaction functions can also be accurately classified, with overall accuracy of 0.99 on average. Our approach can provide reasonable suggestions that assist industrial practitioners to identify transaction functions faster and easier.