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E. Kula

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Doctoral thesis (2025) - E. Kula, A. van Deursen, G. Gousios
Late deliveries have been a common problem in the software industry for decades. They often result from deficiencies in effort estimation and project planning. These deficiencies arise due to the complexity of software development, where various social and technical factors affect project effort and scheduling. Variability in human elements, such as team dynamics and changing user requirements, adds further uncertainty. Since meeting time and cost estimates is crucial for project success, improving effort estimation and planning remains a key priority for software organizations. More accurate forecasting enables better resource allocation, reduces delays, and enhances customer satisfaction.

Over the past two decades, software organizations have increasingly adopted agile methods to improve flexibility and responsiveness. However, despite these advantages, schedule delays remain common, with nearly half of agile projects experiencing overruns of 25% or more. A key challenge lies in balancing the flexible, short-term planning of small functionalities (user stories) with the structured, long-term planning required for larger development units (epics). Current industry practices offer limited support for managing these complexities, especially in large-scale agile settings.

This thesis presents a novel suite of expert- and data-based strategies to improve effort estimation and planning in large-scale agile software development. We conduct a series of case studies at ING, a large Dutch internationally operating bank, to collect and analyze data from hundreds of agile teams and projects. We identify key factors influencing delays in epics and user stories and develop models to predict delays at both levels. At the epic level, we compile our findings into a conceptual framework representing influential factors and their relationships to on-time delivery. Additionally, we explore dynamic Bayesian methods to continuously update delay predictions throughout an epic's development life cycle. At the story level, we examine how team characteristics affect the likelihood of delays. We also investigate how these factors, combined with incremental learning methods, can improve story delay predictions. Finally, we develop a model that optimizes sprint plans based on team goals and delivery performance.

Our research identifies 25 factors and their interactions that affect the on-time delivery of epics. The most influential factors are predominantly social in nature, such as task dependencies, organizational alignment, and internal politics. These factors interact hierarchically: organizational factors shape team behavior, which in turn affects technical factors. To capture these complexities, we demonstrate that dynamic Bayesian methods, using delay patterns as input, effectively update delay predictions as new information becomes available. At the story level, our findings suggest that planning in agile settings can be significantly improved by integrating team-related information and incremental learning methods into predictive models. Moreover, we find that user story prioritization depends on a combination of factors that vary by project context. Our sprint plan optimization model effectively addresses this variability and generates plans that deliver more business value, align more closely with sprint goals, and mitigate delay risks better. ...
Conference paper (2024) - Elvan Kula, Arie Van Deursen, Georgios Gousios
Sprint planning is essential for the successful execution of agile software projects. While various prioritization criteria influence the selection of user stories for sprint planning, their relative importance remains largely unexplored, especially across different project contexts. In this paper, we investigate how prioritization criteria vary across project settings and propose a model for generating sprint plans that are tailored to the context of individual teams. Through a survey conducted at ING, we identify urgency, sprint goal alignment, and business value as the top prioritization criteria, influenced by project factors such as resource availability and client type. These results highlight the need for contextual support in sprint planning. To address this need, we develop an optimization model that generates sprint plans aligned with the specific goals and performance of a team. By integrating teams' planning objectives and sprint history, the model adapts to unique team contexts, estimating prioritization criteria and identifying patterns in planning behavior. We apply our approach to real-world data from 4,841 sprints at ING, demonstrating significant improvements in team alignment and sprint plan effectiveness. Our model boosts team performance by generating plans that deliver more business value, align more closely with sprint goals, and better mitigate delay risks. Overall, our results show that the efficiency and outcomes of sprint planning practices can be significantly improved through the use of context-aware optimization methods. ...
Conference paper (2023) - E. Kula, Eric Greuter, A. van Deursen, G. Gousios
Modern agile software projects are subject to constant change, making it essential to re-asses overall delay risk throughout the project life cycle. Existing effort estimation models are static and not able to incorporate changes occurring during project execution. In this paper, we propose a dynamic model for continuously predicting overall delay using delay patterns and Bayesian modeling. The model incorporates the context of the project phase and learns from changes in team performance over time. We apply the approach to real-world data from 4,040 epics and 270 teams at ING. An empirical evaluation of our approach and comparison to the state-of-the-art demonstrate significant improvements in predictive accuracy. The dynamic model consistently outperforms static approaches and the state-of-the-art, even during early project phases. ...
Journal article (2022) - Elvan Kula, Eric Greuter, Arie Van Deursen, Gousios Georgios
Late delivery of software projects and cost overruns have been common problems in the software industry for decades. Both problems are manifestations of deficiencies in effort estimation during project planning. With software projects being complex socio-technical systems, a large pool of factors can affect effort estimation and on-time delivery. To identify the most relevant factors and their interactions affecting schedule deviations in large-scale agile software development, we conducted a mixed-methods case study at ING: two rounds of surveys revealed a multitude of organizational, people, process, project and technical factors which were then quantified and statistically modeled using software repository data from 185 teams. We find that factors such as requirements refinement, task dependencies, organizational alignment and organizational politics are perceived to have the greatest impact on on-time delivery, whereas proxy measures such as project size, number of dependencies, historical delivery performance and team familiarity can help explain a large degree of schedule deviations. We also discover hierarchical interactions among factors: organizational factors are perceived to interact with people factors, which in turn impact technical factors. We compose our findings in the form of a conceptual framework representing influential factors and their relationships to on-time delivery. Our results can help practitioners identify and manage delay risks in agile settings, can inform the design of automated tools to predict schedule overruns and can contribute towards the development of a relational theory of software project management. ...
Conference paper (2021) - Elvan Kula, Arie van Deursen, Georgios Gousios
In agile software development, proper team structures and effort estimates are crucial to ensure the on-time delivery of software projects. Delivery performance can vary due to the influence of changes in teams, resulting in team dynamics that remain largely unexplored. In this paper, we explore the effects of various aspects of teamwork on delays in software deliveries. We conducted a case study at ING and analyzed historical log data from 765,200 user stories and 571 teams to identify team factors characterizing delayed user stories. Based on these factors, we built models to predict the likelihood and duration of delays in user stories. The evaluation results show that the use of team-related features leads to a significant improvement in the predictions of delay, achieving on average 74%-82% precision, 78%-86% recall and 76%-84% F-measure. Moreover, our results show that team-related features can help improve the prediction of delay likelihood, while delay duration can be explained exclusively using them. Finally, training on recent user stories using a sliding window setting improves the predictive performance; our predictive models perform significantly better for teams that have been stable. Overall, our results indicate that planning in agile development settings can be significantly improved by incorporating team-related information and incremental learning methods into analysis/predictive models. ...

An Exploratory Case Study at ING

Conference paper (2019) - E. Kula, Ayushi Rastogi, Hennie Huijgens, Arie van Deursen, Georgios Gousios
The appeal of delivering new features faster has led many software projects to adopt rapid releases. However, it is not well understood what the effects of this practice are. This paper presents an exploratory case study of rapid releases at ING, a large banking company that develops software solutions in-house, to characterize rapid releases. Since 2011, ING has shifted to a rapid release model. This switch has resulted in a mixed environment of 611 teams releasing relatively fast and slow. We followed a mixed-methods approach in which we conducted a survey with 461 participants and corroborated their perceptions with 2 years of code quality data and 1 year of release delay data. Our research shows that: rapid releases are more commonly delayed than their non-rapid counterparts, however, rapid releases have shorter delays; rapid releases can be beneficial in terms of reviewing and user-perceived quality; rapidly released software tends to have a higher code churn, a higher test coverage and a lower average complexity; challenges in rapid releases are related to managing dependencies and certain code aspects, e.g. design debt. ...