In version control systems such as Git, concurrent modifications on the same artifacts can cause merge conflicts that may disrupt the development workflow by requiring manual intervention. While research on software merging focused on sophisticated techniques that hardly had any impact in practice, we present an empirical feasibility study on semi-automated conflict resolution using a fixed set of only a few language-agnostic conflict resolution patterns. In a large-scale quantitative analysis, we simulate the performance of our hypothetical conflict resolution strategy by classifying 131,154 merge conflict resolutions of a diverse sample of 10,000 GitHub projects according to these resolution patterns. We shed light on the derivability of merges on multiple levels of granularity: the conflicting merge commit, its conflicting files and their individual conflicting chunks. 87.9% of chunks are derivable individually, while 34.5% of merges are derivable as a whole. Interestingly, however, by inspecting potential factors affecting derivability, we observe that there are stronger correlations considering individual files than considering the entire merge. A short yet preliminary answer to whether semi-automated conflict resolution is easier than we expected is: yes, it might be, particularly if we use the right level of granularity for proposing conflict resolutions. Through our comprehensive analysis, we aspire to bridge the gap between academic innovations on sophisticated merge techniques and real-world merge conflict scenarios, laying the groundwork for more effective and widely accepted automatic merge tools.

Design by Contract represents an established, lightweight paradigm for engineering reliable and robust software systems by specifying verifiable expectations and obligations between software components. Due to its laborious nature, developers hardly adopt Design by Contract in practice. A plethora of research on (semi-)-automated inference to reduce the manual burden has not improved the adoption of so-called code contracts in practice. This paper examines the potential of Generative AI to automatically generate code contracts in terms of pre- and postconditions for any Java project without requiring any additional auxiliary artifact. To fine-tune two state-of-the-art Large Language Models, CodeT5 and CodeT5+, we derive a dataset of more than 14k Java methods comprising contracts in form of Java Modeling Language (JML) annotations, and train the models on the task of generating contracts. We examine the syntactic and semantic validity of the contracts generated for software projects not used in the fine-tuning and find that more than 95% of the generated contracts are syntactically correct and exhibit remarkably high completeness and semantic correctness. To this end, our fully automated method sets the stage for future research and eventual broader adoption of Design by Contract in software development practice.

Bug reports are essential software artifacts that describe software bugs using natural language. Bug localization tools can help developers to understand the relation between bug reports and a software system. However, most approaches for localizing bugs work with unstructured textual information from the source codes and bug reports. This paper proposes an approach for locating and visualizing bug reports based on class diagrams representing the overall structural design of a software system. Our approach called IdentiBug takes advantage of deep learning techniques to train our bug localization model to predict connections between a bug report and the system’s class diagram. The result is a ranked list of classes from which we extract and rank a list of class diagram excerpts for assisting the developers during bug documentation and localization.

Models in Model-driven Engineering are primary development artifacts that are heavily edited in all stages of software development and that can become temporarily inconsistent during editing. In general, there are many alternatives to resolve an inconsistency, and which one is the most suitable depends on a variety of factors. As also proposed by recent approaches to model repair, it is reasonable to leave the actual choice and approval of a repair alternative to the discretion of the developer. Model repair tools can support developers by proposing a list of the most promising repairs. Such repair recommendations will be only accepted in practice if the generated proposals are plausible and understandable, and if the set as a whole is manageable. Current approaches, which mostly focus on exhaustive search strategies, exploring all possible model repairs without considering the intention of historic changes, fail in meeting these requirements. In this article, we present a new approach to generate repair proposals that aims at inconsistencies that have been introduced by past incomplete edit steps that can be located in the version history of a model. Such an incomplete edit step is either undone or it is extended to a full execution of a consistency-preserving edit operation. The history-based analysis of inconsistencies as well as the generation of repair recommendations are fully automated, and all interactive selection steps are supported by our repair tool called R E V ISION . We evaluate our approach using histories of real-world models obtained from popular open-source modeling projects hosted in the Eclipse Git repository, including the evolution of the entire UML meta-model. Our experimental results confirm our hypothesis that most of the inconsistencies, namely, 93.4, can be resolved by complementing incomplete edits. 92.6% of the generated repair proposals are relevant in the sense that their effect can be observed in the models’ histories. 94.9% of the relevant repair proposals are ranked at the topmost position.

Model slicers are tools which provide two services: (a) finding parts of interest in a model and (b) displaying these parts somehow or extract these parts as a new, autonomous model, which is referred to as slice or sub-model. This paper focuses on the creation of editable slices, which can be processed by model editors, analysis tools, model management tools etc. Slices are useful if, e.g., only a part of a large model shall be analyzed, compared or processed by time-consuming algorithms, or if sub-models shall be modified independently. We present a new generic incremental slicer which can slice models of arbitrary type and which creates slices which are consistent in the sense that they are editable by standard editors. It is built on top of a model differencing framework and does not require additional configuration data beyond those available in the differencing framework. The slicer can incrementally extend or reduce an existing slice if model elements shall be added or removed, even if the slice has been edited meanwhile. We demonstrate the usefulness of our slicer in several scenarios using a large UML model. A screencast of the demonstrated scenarios is provided at http://pi.informatik.uni-siegen.de/projects/SiLift/ase2017.

Model-based development has become a widely-used approach to implement software, e.g. for embedded systems. Models replace source code as primary executable artifacts in these cases. Software product line technologies for these domains must be able to generate models as instances of an SPL. This need is addressed among others by an implementation technology for SPLs known as delta modeling. Current approaches to delta modeling require deltas to be written manually using delta languages, and they offer only very limited support for creating and testing a network of deltas. This paper presents a new approach to delta modeling and a supporting tool suite: the abstract notion of a delta is refined to be a consistency-preserving edit script which is generated by comparing two models. The rich structure of edit scripts allows us to detect conflicts and further relations between deltas statically and to implement restructurings in delta sets such as the merging of two deltas. We illustrate the tooling using a case study.

In model-based software development, models are primary artifacts which iteratively evolve and which have many versions during their lifetime. A clear representation of the changes between different versions of a model is the key to understanding and successfully managing the evolution of a model-based system. However, model comparison tools currently available display model differences on a low level of abstraction, namely in terms of basic graph operations on the abstract syntax graph of a model. These low-level model differences are often hard or even impossible to understand for normal tool users who are not familiar with meta-models. In this paper we present SiLift, a generic tool environment which is able to semantically lift low-level differences of EMF-based models into representations of user-level edit operations.