Keywords: model versioning, model-driven development, collaboration, conflict resolution
Astract: The advances in software development lead to ever increasing complexity of software systems.
Therewith rises the demand for technologies and techniques to shield the developers from that system complexity. For decades researchers and practioners have created abstractions to that end. Early programming languages shielded the programmers from the complexity of programming with machine code. Continuously, new programming languages and environments emerged and still emerge. At the moment, model-driven development, the next abstraction level, is on the rise, leveraging models to central artefacts of software development.
Nowadays, software is developed in teams. Models provide the advantage to be additionally used as an inter-expert language, hence facilitating communication. Consequently, a model is often edited by multiple persons. Version control provides collaborative support on a technical level by enabling concurrent work. In version control, mechanisms are refined to improve software development in teams. Current versioning tools, however, mainly provide support for code-centric software engineering. Versioning of models still faces major challenges. Models may not be as easily divided into parts and partitioned for several developers to work on as source code is. Due to parallel development, the versioning of models is especially prone to conflicts. The resolution of conflict situations is a precarious and preferably collaborative process. Progress in model-driven development research seems to be restricted to the technical level, while social aspects like human behaviour and cooperation are often neglected. This is surprising, since software developers spend more than 60% of their time with collaborative activities, including meetings and other communication, coordination of tasks, and collaboratively executing these tasks. Well working collaboration in a team leads to an overall better outcome. It is therefore important to actively shape collaboration to gain the huge potential benefits achieved through efficient teamwork.
This thesis provides a general survey on possibilities to improve the model-driven development process in regard to collaborative aspects. We therefore analyse means and methods of collaboration in theory and practice, both in software engineering and various other fields. We highlight the importance of attaching a greater value to collaboration in research and in practice. Since collaboration is especially finical in conflict situations, we provide a specific example for enhanced collaboration in conflict resolution in model versioning.

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Astract: Model-Driven Engineering places models as first-class artifacts throughout the software lifecycle requiring the availability of proper transformation languages. Although numerous approaches are available, they lack convenient facilities for supporting debugging and understanding of the transformation logic. This is because execution engines operate on a low level of abstraction, hide the operational semantics of a transformation, scatter metamodels, models, transformation logic, and trace information across different artifacts, and provide limited verification support. To tackle these problems, we propose a Domain-Specific Language (DSL) on top of Colored Petri Nets (CPNs)-called Transformation Nets-for the execution and debugging of model transformations on a high level of abstraction. This formalism makes the afore hidden operational semantics explicit by providing a runtime model in terms of places, transitions and tokens, integrating all artifacts involved into a homogenous view. Moreover, the formal underpinnings of CPNs enable comprehensive verification of model transformations.

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Astract: United Nation's Centre for Trade Facilitation and Electronic Business (UN/CEFACT) is an e-business standardization body known for its work on UN/EDIFACT and ebXML. One of its on-going work items is the UN/CEFACT Modeling Methodology (UMM) for modeling global choreographies of B2B scenarios. The work on UMM started in 1998 and has improved since then by contributions from participating organizations, such as RosettaNet, SWIFT, GS 1. Today, all new UN/CEFACT standards for data exchange scenarios must be backed up by a corresponding UMM model. In this paper, we revisit the UMM version 1.0 that is defined as a UML 1.4 profile. We introduce the main concepts of UMM and elaborate on the strengths and weaknesses of UMM 1.0. Being the editorial team of UMM, we have made improvements to UMM, which will be released shortly as a new standard version. Thus, we elaborate on the new concepts of UMM 2.0 that are further illustrated by means of a simple example.

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Astract: Ever faster changing market conditions require businesses to frequently adapt their business processes and the underlying workflow systems. Serviceoriented architectures are said to deliver this flexibility by loose coupling. In this chapter we provide a survey on realizing flexible workflows on top of service oriented architectures.We show how orchestrations and choreographies may be implemented by state-of-the-art web services technology. The role of agents in realizing workflows among services is discussed. Furthermore, we discuss service provision in dynamic environments, when partners are dynamically bound to the workflow and when changes to the workflow schema happen.

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Astract: Adequate IT support for Business-to-Business integration(B2Bi) is indispensable in today´s globalized world. Agreement among personnel from different enterprises as well as distributed computing issues are major challenges to the automation of B2Bi processes. These challenges can be addressed by applying the choreography language ebXML BPSS (ebBP) for declaratively specifying B2Bi processes and using Web services and WS-BPEL as dedicated integration technologies. ebBP Business Transactions (BT) are the primary building block of ebBP choreographies and specify the exchange of up to two business documents in a declarative and technology-agnostic way. Composing BTs within choreographies and realization of QoS raise important requirements for the orchestration layer. This paper investigates these requirements and presents a composable, abstract, flexible and QoS-aware execution model that can be implemented using Web Services and BPEL.

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Astract: In optimistic versioning, multiple developers are allowed to modify an artifact at the same time. On the one hand this approach increases productivity as the development process is never stalled due to locks on an artifact. On the other hand conflicts may arise when it comes to merging the different modifications into one consolidated version. In general, the resolution of such conflicts is not only cumbersome, but also error-prone. Especially if the artifacts under version control are models, little support is provided by standard versioning systems. In this paper we present the enhanced versioning process of the model versioning system AMOR. We show how AMOR is configured in order to obtain a precise conflict report which allows the recommendation of automatically executable resolution patterns. The user of AMOR chooses either one of the recommendations or performs manual resolution. The manual resolution may be in collaboration with other developers and allows to infer new resolution patterns which may be applied in similar situations.

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Astract: During the last decade several approaches have been proposed for easing the burden of writing model transformation rules manually. Among them are Model Transformation By-Demonstration (MTBD) approaches which record actions performed on example models to derive general operations. A current restriction of MTBD is that until now they are only available for in-place transformations, but not for model-to-model (M2M) transformations. In this paper, we extend our MTBD approach, which is designed for in-place transformations, to also support M2M transformations. In particular, we propose to demonstrate each transformation rule by modeling a source model fragment and a corresponding target model fragment. From these example pairs, the applied edit operations are computed which are input for a semi-automatic process for deriving the general transformation rules. For showing the applicability of the approach, we developed an Eclipse-based prototype supporting the generation of ATL code out of EMF-based example models.

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Astract: Model transformations play a key role in the vision of Model-Driven Engineering. Nevertheless, mechanisms like abstraction, variation and composition for specifying and applying reusable model transformations - like urgently needed for resolving recurring structural heterogeneities - are insufficiently supported so far. Therefore, we propose to specify model transformations by a set of pre-defined mapping operators (MOps), each resolving a certain kind of structural heterogeneity. Firstly, these MOps can be used in the context of arbitrary metamodels since they abstract from concrete metamodel types. Secondly, MOps can be tailored to resolve certain structural heterogeneities by means of black-box reuse. Thirdly, based on a systematic set of kernel MOps resolving basic heterogeneities, composite ones can be built in order to deal with more complex scenarios. Finally, an extensible library of MOps is proposed, allowing for automatically executable mapping specifications since every MOp exhibits a clearly defined operational semantics.