Context: Systematic literature studies, such as secondary studies, are crucial to aggregate evidence. An essential part of these studies is the selection phase of relevant studies. This, however, is time-consuming, resource-intensive, and error-prone as it highly depends on manual labor and domain expertise. The increasing popularity of Large Language Models (LLMs) raises the question to what extent these manual study selection tasks could be supported in an automated manner.

Objectives: In this manuscript, we report on our effort to explore and evaluate the use of state-of-the-art LLMs to automate the selection phase in systematic literature studies.

Method: We evaluated LLMs for the selection phase using two published systematic literature studies in software engineering as ground truth. Three prompts were designed and applied across five LLMs to the studies’ titles and abstracts based on their inclusion and exclusion criteria. Additionally, we analyzed combining two LLMs to replicate a practical selection phase. We analyzed recall and precision and reflected upon the accuracy of the LLMs, and whether the ground truth studies were conducted by early career scholars or by more advanced ones.

Results: Our results show a high average recall of up to 98% combined with a precision of 27% in a single LLM approach and an average recall of 99% with a precision of 27% in a two-model approach replicating a two-reviewer procedure. Further the Llama 2 models showed the highest average recall 98% across all prompt templates and datasets while GPT4-turbo had the highest average precision 72%.

Conclusions: Our results demonstrate how LLMs could support a selection phase in the future. We recommend a two LLM-approach to archive a higher recall. However, we also critically reflect upon how further studies are required using other models and prompts on more datasets to strengthen the confidence in our presented approach. © 2025 The Authors

Context: Automated analysis of code review comments (CRCs) can aid in highlighting frequently discussed issues by reviewers from large repositories. Topic modeling is a promising approach to analyzing large natural language repositories. However, CRCs contain natural language text and code references; thus, data pre-processing and topic modeling approaches must be carefully selected.

Objective: This work aims to discuss the various decisions taken and considerations involved in the analysis of CRCs.

Method: We utilized 5,560 CRCs from an open-source system to study the decisions and considerations faced during the analysis of CRCs using topic modeling, followed by an evaluation of the interpretability of identified themes by a domain expert.

Results: We report several observations and challenges in improving the quality of the identified themes, including choices regarding the pre-processing, topic modeling parameters, embedding model, and objective measures of coherence used, which impact the subjective interpretability of the identified themes.

Conclusions: This work offers unique considerations, and the impact of these decisions can facilitate future studies in conducting topic modeling-based analyses of CRCs. Future studies can utilize the technical demonstrator to explore the interpretability of the topics generated from CRCs. 

Context: Code reviewers provide valuable feedback during the code review. Identifying common issues described in the reviewers’ feedback can provide input for devising context-specific software development improvements. However, the use of reviewer feedback for this purpose is currently less explored.

Objective: In this study, we assess how automation can derive more interpretable and informative themes in reviewers’ feedback and whether these themes help to identify recurring quality-related issues in code changes.

Method: We conducted a participatory case study using the JabRef system to analyze reviewers’ feedback on merged and abandoned code changes. We used two promising topic modeling methods (GSDMM and BERTopic) to identify themes in 5,560 code review comments. The resulting themes were analyzed and named by a domain expert from JabRef.

Results: The domain expert considered the identified themes from the two topic models to represent quality-related issues. Different quality issues are pointed out in code reviews for merged and abandoned code changes. While BERTopic provides higher objective coherence, the domain expert considered themes from short-text topic modeling more informative and easy to interpret than BERTopic-based topic modeling.

Conclusions: The identified prevalent code quality issues aim to address the maintainability-focused issues. The analysis of code review comments can enhance the current practices for JabRef by improving the guidelines for new developers and focusing discussions in the developer forums. The topic model choice impacts the interpretability of the generated themes, and a higher coherence (based on objective measures) of generated topics did not lead to improved interpretability by a domain expert. 

Context: Several secondary studies have investigated the relationship between internal quality attributes, source code metrics and external quality attributes. Sometimes they have contradictory results. Objective: We synthesize evidence of the link between internal quality attributes, source code metrics and external quality attributes along with the efficacy of the prediction models used. Method: We conducted a tertiary review to identify, evaluate and synthesize secondary studies. We used several characteristics of secondary studies as indicators for the strength of evidence and considered them when synthesizing the results. Results: From 711 secondary studies, we identified 15 secondary studies that have investigated the link between source code and external quality. Our results show : (1) primarily, the focus has been on object-oriented systems, (2) maintainability and reliability are most often linked to internal quality attributes and source code metrics, with only one secondary study reporting evidence for security, (3) only a small set of complexity, coupling, and size-related source code metrics report a consistent positive link with maintainability and reliability, and (4) group method of data handling (GMDH) based prediction models have performed better than other prediction models for maintainability prediction. Conclusions: Based on our results, lines of code, coupling, complexity and the cohesion metrics from Chidamber & Kemerer (CK) metrics are good indicators of maintainability with consistent evidence from high and moderate-quality secondary studies. Similarly, four CK metrics related to coupling, complexity and cohesion are good indicators of reliability, while inheritance and certain cohesion metrics show no consistent evidence of links to maintainability and reliability. Further empirical studies are needed to explore the link between internal quality attributes, source code metrics and other external quality attributes, including functionality, portability, and usability. The results will help researchers and practitioners understand the body of knowledge on the subject and identify future research directions. © 2023 The Author(s)

Context: Code reviewers provide valuable feedback during the code review. Identifying common issues described in the reviewers' feedback can provide input for context-specific software improvement opportunities. However, the use of reviewer feedback for this purpose is currently less explored.

Objective: Assessing if and how automation can derive themes in reviewers' feedback and whether these themes help to identify recurring quality-related issues in code changes.

Method: We conducted a case study using the JabRef system to distinguish reviewers' feedback on merged and abandoned code changes for the analysis. We used topic modeling to identify themes in 5,560 code review comments. The resulting themes were analyzed and named by a domain expert from JabRef.

Results: The domain expert considered the identified themes from the proposed automation approach to represent quality-related issues. We found that different quality issues are pointed out in code reviews for merged and abandoned code changes. 

Conclusions: The results indicate the usefulness of our proposed automation approach in utilizing code review comments for understanding the prevalent code quality issues that can help derive targeted and context-bound improvement actions.

Context: Software quality has a multi-faceted description encompassing several quality attributes. Central to our efforts to enhance software quality is to improve the quality of the source code. Poor source code quality impacts the quality of the delivered product. Empirical studies have investigated how to improve source code quality and how to quantify the source code improvement. However, the reported evidence linking internal code structure information and quality attributes observed by users is varied and, at times, conflicting. Furthermore, there is a further need for research to improve source code quality by understanding trends in feedback from code review comments.

Objective: This thesis contributes towards improving source code quality and synthesizes metrics to measure improvement in source code quality. Hence, our objectives are 1) To synthesize evidence of links between source code metrics and external quality attributes, & identify source code metrics, and 2) To identify areas to improve source code quality by identifying recurring code quality issues using the analysis of code review comments.

Method: We conducted a tertiary study to achieve the first objective, an archival analysis and a case study to investigate the latter two objectives.

Results: To quantify source code quality improvement, we reported a comprehensive catalog of source code metrics and a small set of source code metrics consistently linked with maintainability, reliability, and security. To improve source code quality using analysis of code review comments, our explored methodology improves the state-of-the-art with interesting results.

Conclusions: The thesis provides a promising way to analyze themes in code review comments. Researchers can use the source code metrics provided to estimate these quality attributes reliably. In future work, we aim to derive a software improvement checklist based on the analysis of trends in code review comments.

Context: A large number of source code metrics are reported in the literature. It is necessary to systematically collect, describe and classify source code metrics to support research and practice.Objective: We aim to utilize existing secondary studies to develop a cat- alog of source code metrics together with their descriptions. The catalog will also provide information about which units of code (e.g., operators, operands, lines of code, variables, parameters, code blocks, or functions) are used to measure the internal quality attributes and the scope on which they are collected. 

Method: We conducted a tertiary study to identify secondary studies re- porting source code metrics. We have classified the source code metrics according to the measured internal quality attributes, the units of code used in the measures, and the scope at which the source code metrics are collected. 

Results: From 711 secondary studies, we identified 52 relevant secondary studies. We reported 423 source code metrics together with their de- scriptions and the internal quality attributes they measure. Source code metrics predominantly incorporate function as a unit of code to measure internal quality attributes. In contrast, several source code metrics use more than one unit of code when measuring internal quality attributes. Nearly 51% of the source code metrics are collected at the class scope, while almost 12% and 15% of source code metrics are collected at module and application levels, respectively. 

Conclusions: Researchers and practitioners can use the extensive catalog to assess which source code metrics meet their individual needs based on the description and classification scheme presented. 

Context: The modern code review process is considered an essential quality assurance step in software development. The code review comments generated can provide insights regarding source code quality and development practices. However, the large number of code review comments makes it challenging to identify interesting patterns manually. In a recent study, Wen et al. used traditional topic modeling to analyze the evolution of code review comments. Their approach could identify interesting patterns that may lead to improved development practices.Objective: In this study, we investigate potential improvements to Wen et al.'s state-of-the-art approach to analyze the evolution of code review comments.Method: We used 209,166 code review comments from three open-source systems to explore and empirically analyze alternative design and implementation choices and demonstrate their impact.Results: We identified the following potential improvements to the current state-of-the-art as described by Wen et al.: 1) utilize a topic modeling method that is optimized for short texts, 2) a refined approach for identifying a suitable number of topics, and 3) a more elaborate approach for analyzing topic evolution. Our results indicate that the proposed changes have quantitatively different results than the current approach. The qualitative interpretation of the topics generated with our changes indicates their usefulness.Conclusions: Our results indicate the potential usefulness of changes to state-of-the-art approaches to analyzing the evolution of code review comments, with practical implications for researchers and practitioners. However, further research is required to compare the effectiveness of both approaches. © 2023 IEEE.