Konrad Wieland

An Example Is Worth a Thousand Words: Composite Operation Modeling By-Example

Predefined composite operations are handy for efficient modeling, e.g., for the automatic execution of refactorings, and for the introduction of patterns in existing models. Some modeling environments provide an initial set of basic refactoring operations, but hardly offer any extension points for the user. Even if extension points exist, the introduction of new composite operations requires programming skills and deep knowledge of the respective metamodel. In this paper, we introduce a method for specifying composite operations within the users modeling language and environment of choice. The user models the composite operation by-example, which enables the semi-automatic derivation of a generic composite operation specification. This specification may be used in various modeling scenarios, like model refactoring and model versioning. We implemented the approach in the Operation Recorder and performed an evaluation by defining multiple complex refactorings for UML diagrams.

EMF Profiles: A Lightweight Extension Approach for EMF Models.

Domain-Specific Modeling Languages (DSMLs) are getting more and more attention as a key element of Model Driven Engineering. As any other software artifact, DSMLs should continuously evolve to adapt to the changing needs of the domain they represent. Unfortunately, right now evolution of DSMLs is a costly process that requires changing the DSML metamodel and re-creating the complete modeling environment. In this paper we advocate for the use of EMF Profiles, an adaptation of the UML Profile concept to DSMLs. Profiles have been a key enabler for the success of UML by providing a lightweight language-inherent extension mechanism which is expressive enough to cover an important subset of extension scenarios. We believe a similar concept for DSMLs would provide a valuable extension mechanism which has been so far neglected by current metamodeling tools. Apart from direct metamodel profiles, we also propose reusable profile definition mechanisms whereby profiles are defined independently of any DSML and, later on, coupled with all DSMLs that can benefit from these profiles. Our approach has been implemented in a prototype integrated in the EMF environment.

An introduction to model versioning

With the emergence of model-driven engineering (MDE), software models are considered as central artifacts in the software engineering process, going beyond their traditional use as sketches. In MDE, models rather act as the single source of information for automatically generating executable software. This shift poses several new research challenges. One of these challenges constitutes model versioning, which targets at enabling efficient team-based development of models. This compelling challenge induced a very active research community, who yielded remarkable methods and techniques ranging from model differencing to merging of models. In this tutorial, we give an introduction to the foundations of model versioning, the underlying technologies for processing models and their evolution, as well as the state of the art in model versioning. Thereby, we aim at equipping students and researchers alike that are new to this domain with enough information for commencing to contribute to this challenging research area.

A posteriori operation detection in evolving software models

Highlights ► Detection of applications of composite operations in evolving software models. ► Automatic generation of detection rules from executable operation specifications. ► Real-world study showing that 70% of all applied composite operations can be detected. ► Performance analysis showing that detection algorithm scales well for large models.

We can work it out: Collaborative Conflict Resolution in Model Versioning

For the versioning of code a pantheon of version control system (VCS) solutions has been realized and is successfully applied in practice. Nevertheless, when it comes to merging two different versions of one artifact, the resolution of conflicts poses a major challenge. In standard systems, the developer who performs the later commit is sole in charge of this often time-consuming, error-prone task. This commit carries the inherent danger of losing the modifications of the other developer. Recently, collaborative merge approaches for code versioning systems have been proposed to minimize this risk. In this paper we propose to apply similar techniques in the context of model versioning where the challenge of merging two versions is even more formidable due to their graph-structure and their rich semantics. In particular, modeling is used in the early phases of the software development, where a collaborative merge is beneficial to elaborate a consolidated understanding of a domain.

Turning Conflicts into Collaboration

In model-driven software development, software models are the main artifacts used not only for supporting brainstorming, analysis, and design purposes, but also for generating executable code. Such software models are usually not created by one single developer, but within a team. To coordinate team work, versioning systems have proven to be indispensable for managing modifications performed by different modelers at the same time. When concurrently performed modifications are contradicting each other, the standard versioning paradigm requires the person who detected the conflict to resolve it immediately in order to keep the evolved artifacts in a consistent state. Whereas this approach works well in later phases of the software development process, in early phases, when the development team had not established a consolidated view on the system under development yet, the conflicts might provide valuable information on the various intentions of the modelers. This information might be lost if removed in an undocumented manner by a single modeler. We propose an alternative versioning paradigm for models, where conflicts are temporarily tolerated and discuss its technical realization for current modeling languages such as the UML. The resolution of conflicts is then not performed by one single modeler but within a team so that a consolidated version of the model is obtained.

From UML profiles to EMF profiles and beyond

Domain-Specific Modeling Languages (DSMLs) are getting more and more attention as a key element of Model Driven Engineering. As any other software artefact, DSMLs should continuously evolve to adapt to the changing needs of the domain they represent. Unfortunately, right now evolution of DSMLs is a costly process that requires changing its metamodel and re-creating the complete modeling environment. In this paper we advocate for the use of EMF Profiles, an adaptation of the UML profile concept to DSMLs. Profiles have been a key enabler for the success of UML by providing a lightweight language-inherent extension mechanism which is expressive enough to cover an important subset of adaptation scenarios. We believe a similar concept for DSMLs would provide an easier extension mechanism which has been so far neglected by current metamodeling tools. Apart from direct metamodel profiles, we also propose reusable profile definition mechanisms whereby profiles are defined independently of any DSML and, later on, coupled with all DSMLs that can benefit from these profiles. Our approach has been implemented in a prototype integrated in the EMF environment.

Colex: a web-based collaborative conflict lexicon

While graphical modeling languages gained recognition as being a promising successor of third-generation programming languages, their widespread employment is still decelerated by the absence of adequate version control management for modeling artifacts. Even worse, the expected behavior and quality requirements for upcoming model versioning systems are only vaguely stated and understood. When it comes to defining, detecting, and resolving conflicts, no consolidated categorization and no common benchmark exist which impedes a uniform comparison of current approaches. With this paper, we invite the model versioning community to conjointly accomplish a consolidated body of knowledge which documents various types of conflicts, their detectability, as well as applicable resolution strategies. Therefore, we present Colex, an open, web-based, collaborative conflict lexicon. As a starting point, we provide a causal categorization of conflicts and---according to these categories---a set of versioning examples.

The operation recorder: specifying model refactorings by-example

Predefined composite operations are handy for efficient software modeling, e.g., for the automatic execution of refactorings, and for the introduction of patterns in existing models. Some modeling environments provide an initial set of basic refactoring operations, but hardly offer any extension points for the user. Even if extension points exist, the introduction of new composite operations requires programming skills and deep knowledge of the respective metamodel. In our demonstration we present the Operation Recorder, a tool for specifying composite operations, like refactorings, within the users modeling language and environment of choice. The user models the composite operation by-example, which enables the semi-automatic derivation of a generic composite operation specification. This specification may be used in further modeling scenarios, like model refactoring and model versioning. We demonstrate our tool by creating two refactoring specifications for UML class diagrams and UML state machine diagrams.

Conflicts as first-class entities: a UML profile for model versioning

The urgent demand for optimistic version control support for software models induced active research within the modeling community. Recently, several approaches have been proposed addressing the task of detecting conflicts when merging two concurrently changed versions of a model. In this context, the holistic representation and supportive visualization of detected merge conflicts pose a challenge. In this paper, we present a modeling language independent conflict model comprising all necessary information to profoundly represent merge conflicts. From this conflict model, we leverage the dynamic extension power of UML profiles by introducing a dedicated conflict profile to visually assist modelers in resolving merge conflicts of UML models. As a result, modelers may resolve conflicts in the concrete graphical syntax conducting their familiar UML editors without tool extensions.