The KLU faculty, post-docs, and PhD candidates regularly publish the results of their research in scientific journals. You will find a complete overview of all KLU publications below (e.g. articles in peer-reviewed journals, professional journals, books, working papers, and conference proceedings). Search for relevant terms and keywords, or filter the list by name, year of publication or type of publication. The references include DOIs and abstracts where available, and you can download them to your own reference database or platform. We regularly update the database with new publications.

Conference Proceedings

Copy reference link   DOI: 10.1007/978-3-319-06695-0_22

Abstract: Driven by rising competitive constraints companies began to outsource at least parts of their internal activities to specialized external logistics providers in terms of contracts. Thereby, new business models like the fourth party logistics evolved, which acts like coordinator of the emerging logistics networks. The main task of the provider is the planning, monitoring and measurement of the different networks of its customers. Based on a method to integrate process modeling and their simulation, complex event processing to gather real-time information about process executions and service profiles to measure subsequent service providers’ quality – a closed loop approach for improving the quality of service provisioning is presented.

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Copy reference link   DOI: 10.1109/ICWS.2014.30

Abstract: The design of applications that comply to the REST architectural style requires observing a given set of architectural constraints. Following these constraints and therefore designing REST compliant applications is a non-trivial task often not fulfilled properly. There exist several approaches for the modeling and formal description of REST applications, but most of them do not pay any attention to how these approaches can support or even force REST compliance. In this paper we propose a model-driven approach for modeling REST services. We introduce a multi layered model which enables (partially) enforcing REST compliance by separating different concerns through separate models. We contribute a multi layered meta-model for REST applications, discuss the connection to REST compliance and show an implementation of our approach based on the proposed meta-model and method. As a result our approach provides a holistic method for the design and realization of REST applications exhibiting the desired level of compliance to the constraints of the REST architectural style.

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Copy reference link   DOI: 10.5220/0004852402760286

Abstract: Service orientation has significantly facilitated the development of complex distributed systems spanning multiple organizations. However, different application areas approach such systems in domain-specific ways, focusing only on particular aspects relevant for their application types. As a result, we observe a very fragmented landscape of service-oriented systems, which does not enable collaboration across organizations. To address this concern, in this work we introduce the notion of Collaborative, Dynamic and Complex (CDC) systems and position them with respect to existing technologies. In addition, we present how CDC systems are modeled and the steps to provision and execute them. Furthermore, we contribute an architecture and prototypical implementation, which we evaluate by means of a case study in a Cloud-enabled context-aware pervasive application.

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Abstract: Collective adaptive systems provide secure and robust collaboration between heterogeneous entities such as humans and computer systems. Such entities have potentially conflicting goals that attempt to satisfy by interacting with each other. Understanding and analyzing their behavior and evolution requires technical, social and economic aspects of modeling. In this paper, we develop a new design principle to describe an integrated and multimodal urban mobility system and model the interactions of various entities by means of game theoretic techniques.

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Copy reference link   DOI: 10.1109/EDOC.2014.24

Abstract: One of the key strengths of service oriented architectures, the concept of service composition to reuse and combine existing services in order to achieve new and superior functionality, promises similar advantages when applied to resources oriented architectures. The challenge in this context is how to realize service composition in compliance with the constraints defined by the REST architectural style and how to realize it in a way that it can be integrated to and benefit from existing service composition solutions. Existing approaches to REST service composition are mostly bound to the HTTP protocol and often lack a systematic methodology and a mature and standards based realization approach. In our work, we follow a comprehensible methodology by deriving the key requirements for REST service composition directly from the REST constraints and then mapping these requirements to a standard compliant extension of the BPEL composition language. We performed a general requirements analysis for REST service composition, defined a meta model for a corresponding BPEL extension, realized this extension prototypically and validated it based on a real world use case from the eScience domain. Our work provides a general methodology to enable REST service composition as well as a realization approach that enables the combined composition of WSDL and REST services in a mature and robust way.

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Copy reference link   DOI: 10.1109/EDOC.2014.39

Abstract: Current systems for enacting scientific experiments, and in particular simulation workflows, do not support multi-scale and multi-field problems if they are not coupled on the level of the mathematical model. We present a life cycle that utilizes the notion of choreographies to enable the trial-and-error modeling and execution of multi-scale and/or multi-field simulations. The life cycle exhibits two views reflecting the characteristics of modeling and execution in a top-down and bottom-up manner. It defines techniques for composing data-intensive, scientific workflows in more complex simulations in a generic, domain-independent way, and thus provides scientists with means for collaborative and integrated data management based on the workflow paradigm.

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Copy reference link   DOI: 10.1109/UCC.2014.37

Abstract: In many modern systems, applications or services are realized as compositions of multiple existing services that can be enacted by Service Composition Engines (SCEs), which provide the required functionality to enable their definition and execution. SCEs typically use the capabilities of an Enterprise Service Bus (ESB) which serves as the messaging hub between the composed services aiming at ensuring their integration. Together, an SCE and ESB solution comprise the service middleware required for the definition and execution of service-based composite applications. Offering a service middleware solution as a service creates a PaaS offering that allows the service consumers to share the service middleware solution in a multi-tenant manner. However, multi-tenancy support for service middleware solutions remains an open issue. For this purpose, in this work we introduce a general architecture for the realization of a multi-tenant service middleware PaaS solution. This architecture is prototypically realized based on open-source, multi-tenant ESB and SCE solutions. The resulting service middleware provides configurability for service compositions, tenant-aware messaging, and tenant-based administration and management of the SCE and the ESB. We also present an empirical evaluation of the multi-tenant service middleware with focus on the SCE. The results of these experiments show a performance degradation within acceptable limits when scaling the number of tenants and tenant users.

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Copy reference link   DOI: 10.5220/0004937403080314

Abstract: Large-scale systems comprising of multiple heterogeneous entities are directly influenced by the interactions of their participating entities. Such entities, both physical and virtual, attempt to satisfy their objectives by dynamically collaborating with each other, and thus forming collective adaptive systems. These systems are subject to the dynamicity of the entities’ objectives, and to changes to the environment. In this work we focus on the latter, i.e. on providing the means for entities in such systems to model, monitor and evaluate their perceived utility by participating in the system. This allows for them to make informed decisions about their interactions with other entities in the system. For this purpose we propose a utility-based approach for decision making, as well as an architecture that allows for the support of this approach.

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Copy reference link   DOI: 10.1109/SOCA.2014.54

Abstract: The ability to repeat an experiment, known as replicability, is a basic concept of scientific research and also an important aspect in the field of eScience. The principles of Service Oriented Computing (SOC) and Cloud Computing, both based on high runtime dynamicity, are more and more adopted in the eScience domain. Simulation experiments exploiting these principles introduce significant challenges with respect to replicability. Current research activities mainly focus on how to exploit SOC and Cloud for eScience, while the aspect of replicability for such experiments is still an open issue. In this paper we define a general method to identify points of dynamicity in simulation experiments and to handle them in order to enable replicability. We systematically examine different types of service binding strategies, the main source of dynamicity, and derive a method and corresponding architecture to handle this dynamicity with respect to replicability. Our work enables scientists to perform simulation experiments that exploit the dynamicity and flexibility of SOC and Cloud Computing but still are repeatable.

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Copy reference link   DOI: 10.1109/SOCA.2014.9

Abstract: The support of multi-tenancy is an essential requirement for leveraging the full capacity of Cloud computing. Multi-tenancy enables service providers to maximize the utilization of their infrastructure and to reduce the servicing costs per customer, thus indirectly benefiting also the customers. In addition, it allows both providers and consumers to reap the advantages of Cloud-based applications configurable for the needs of different tenants. Nowadays, new applications or services are typically compositions of multiple existing services. Service Composition Engines (SCEs) provide the required functionality to enable the definition and execution of such compositions. Multi-tenancy on the level of SCEs allows for both process model, as well as underlying infrastructure sharing. Towards the goal of enabling multi-tenancy of SCEs, in this paper, we investigate the requirements and define a general architecture for the realization of a multi-tenant SCE solution. This architecture is prototypically realized based on an open-source SCE implementation and integrated into an existing multi-tenant aware Enterprise Service Bus (ESB). The performance evaluation of our prototype shows promising results in terms of the degradation introduced due to processing and communication overhead.

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Copy reference link   DOI: doi:10.1007/978-3-662-45563-0_6

Abstract: Collaborative, Dynamic & Complex (CDC) systems such as adaptive pervasive systems, eScience applications, and complex business systems inherently require modeling and run time flexibility. Since domain problems in CDC systems are expressed as service choreographies and enacted by service orchestrations, we propose an approach introducing placeholder modeling constructs usable both on the level of choreographies and orchestrations, and a classification of strategies for their refinement to executable workflows. These abstract modeling constructs allow deferring the modeling decisions to later points in the life cycle of choreographies. This supports run time scenarios such as incorporating new participants into a choreography after its enactment has started or enhancing the process logic of some of the participants. We provide a prototypical implementation of the approach and evaluate it by means of a case study.

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Copy reference link   DOI: 10.1109/EDOC.2014.25

Abstract: Service selection is an important concept in service oriented architectures that enables the dynamic binding of services based on functional and non-functional requirements. The introduction of the concept of on-demand provisioned services significantly changes the nature of services and as a consequence the traditional service selection process does not fit anymore. Existing approaches for service selection rely on the always on semantic of services, an assumption that is not valid for on-demand provisioned services. We tackle this problem by adapting the traditional service selection process and by defining an additional step covering the changes introduced by the concept of on-demand provisioning. Our solution comprises an extended architecture for on-demand provisioning, a metamodel for a service registry, and a detailed definition and discussion of the adapted and extended service selection process. The work presented in this paper allows keeping the advantages of dynamic service binding at runtime and combining them with the advantages of Cloud computing exploited through the concept of on-demand provisioning.

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Copy reference link   DOI: 10.1007/978-3-319-06695-0_16

Abstract: With the principle of division of labor in logistics, an integrator can focus on planning and monitoring within a network, while subsidiary logistics service providers (LSPs) are responsible for the actual physical manipulation of goods. Because of heterogeneous service descriptions, processes and IT-systems, the integrator requires a platform that provides the ability to interact with LSPs and to plan, execute and monitor contracts for integrator’s customers. Such an integration platform is currently developed in the research project Logistics Service Engineering & Management. Crucial to such a platform is the ability to maintain a complete catalog and to efficiently identify and choose appropriate services. In this paper a metamodel-based approach is presented facing these requirements.

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Copy reference link   DOI: 10.1109/SOCA.2013.35

Abstract: Service orientation has significantly facilitated the development of complex distributed systems spanning multiple organizations. However, different application areas approach such systems in domain-specific ways, focusing on particular aspects relevant only for their application types. As a result, we observe a very fragmented landscape of service-oriented systems, which does not enable collaboration across organizations. To address this concern, in this work we introduce the notion of Collaborative, Dynamic and Complex (CDC) systems and position them with respect to existing technologies. In addition, we present how CDC systems are modeled and the steps to provision and execute them. We also contribute an architecture enabling CDC Systems with full life cycle coverage that allows for leveraging service-oriented and Cloud-related technologies.

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Copy reference link   DOI: 10.1109/SOCA.2013.21

Abstract: Service orientation is a mainstream paradigm in business applications and gains even greater acceptance in the very active field of eScience. In SOC service binding strategies have been defined to specify the point in time a service can be discovered and selected for use, namely static binding, dynamic binding at deployment or at run time, and dynamic service deployment. The basic assumption in all these strategies is that the software stack and infrastructure necessary to execute the services are already available. While in service-based business applications this is typically a valid assumption in scientific applications it is often not the case. Therefore, in this work we introduce a new binding strategy for services we call on-demand provisioning which entails provisioning of the software stack necessary for the service and subsequent dynamic deployment of the service itself. Towards this goal, we also contribute a middleware architecture that enables the provisioning of the software stack - functionality unavailable in conventional service middlewares. We demonstrate the approach and the capabilities of the middleware and the current state of the implementation of our approach. For this purpose we use an example application from the field of eScience that comprises a scientific workflow management system for simulations.

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Abstract: Desicion-makers in and around today's supply chains are facing tough every day. However, when making decisions, they rarely consider what effects their desicions cause upon other participants of the supply chain or traffic management. This is mostly due to the lack of appropriate tools which help indicating the possible effects. Such tools are necessary to tackle the inherent complexity of the whole supply chain system. This paper describes how to construct and design such a tool for this interdisciplinary environment, called an Interdisciplinary Decision Map (IDM). The IDM is a powerful tool to visualise complex relationships, while at the same time retaining usability by showing relevant information only. We show how tu use a specific instance of an IDM to facilitate a better understanding to the underlying processes of other supply chain participants. The soundness of our approach is backed by findings from an interdisciplinary research project.

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Copy reference link   DOI: 10.1109/CloudCom.2013.90

Abstract: Migrating an existing application to the Cloud is a complex and multi-dimensional problem requiring in many cases adapting the application in significant ways. Looking specifically into the database layer of the application, i.e. the aspect providing data persistence and manipulation capabilities, this involves dealing with differences in the granularity of interactions, refactoring of the application to cope with remote data sources, and addressing data confidentiality concerns. Toward this goal, in this work we present an application migration methodology which incorporates these aspects, and a decision support, application refactoring and data migration tool that assists application developers in realizing this methodology. For purposes of evaluating our proposal we present the results of a case study conducted in the context of an eScience project.

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Abstract: Supplies of food and water are essential in disaster management, particularly in the very early chaotic phases when demand and available resources are highly uncertain, information systems are disrupted, and communication between communities, food suppliers, retail and emergency authorities is difficult. As many actors and organisations are involved in ever more complex food supply chains, cooperation and collaboration are vital for efficient and effective disaster management. To support decision-makers facing these problems, this paper introduces a scenario-based approach that integrates simulation of disruptions in food supply chains, and qualitative expert assessment to develop consistent scenarios that show the consequences of different strategies. To choose the best individual measures for all relevant actors and to compare it with the best overall strategy approaches from multi-criteria decision analysis are used.

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Abstract: In this article, basic characteristics of HGV toll systems are described. Based on that, these systems' impacts on entrepreneurial processes and resulting changes in business choices are discussed. Furthermore, a case study on hauliers' reactions on the German HGV toll is presented. The results show that the haulage industry only has to deal with marginal impacts since costs are usually passed along to the customer, this is why operational changes do not seem necessary.

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Copy reference link   DOI: 10.1109/eScience.2012.6404417

Abstract: Simulations are characterized by long running calculations and complex data handling tasks accompanied by non-trivial data dependencies. The workflow technology helps to automate and steer such simulations. Quality of Data frameworks are used to determine the goodness of simulation data, e.g., they analyze the accuracy of input data with regards to the usability within numerical solvers. In this paper, we present generic approaches using evaluated Quality of Data to steer simulation workflows. This allows for ensuring that the predefined requirements such as a precise final result or a short execution time will be met even after the execution of simulation workflow has been started. We discuss mechanisms for steering a simulation on all relevant levels - workflow, service, algorithms, and define a unifying approach to control such workflows. To realize Quality of Data-driven workflows, we present an architecture realizing the presented approach and a WS-Policy-based language to describe Quality of Data requirements and capabilities.

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Abstract: Abstract Using workflows for scientific calculations, experiments and simulations has been a success story in many cases. Unfortunately, most of the existing scientific workflow systems implement proprietary, non-standardized workflow languages, not taking advantage of the achievements of the conventional business workflow technology. It is only natural to combine these two research branches in order to harness the strengths of both. In this demonstration, we present Mayflower, a workflow environment that enables scientists to model workflows on the fly using extended business workflow technology. It supports the typical trial-and-error approach scientists follow when developing their experiments, computations or simulations and provides scientists with all crucial characteristics of the workflow technology. Additionally, beneficial to the business stakeholders, Mayflower brings additional simplification in workflow development and debugging.

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Copy reference link   DOI: 10.1109/SOCA.2012.6449436

Abstract: Profound understanding of business processes is a key success factor for Business Process Management (BPM). As more and more analytical information like runtime data from process execution or statistical data from business intelligence are available, the problem of business process complexity becomes apparent. Process-relevant information needs to be provided as fast as possible while considering easy and fast interpretation and dynamic changes in stakeholders' demands. The static and use-case specific creation or modification of process visualizations shown in current approaches and tools, however, is complex, time consuming, inflexible and thus costly. To address these shortcomings, we introduce a template-based approach that decouples the creation of visualization templates from concrete process visualizations. The binding of customization points of visualization templates to analytical process information is supported by a graphical editor that enables customization of visualizations in a fast and flexible manner. Moreover, due to the separation of concerns, our approach improves the usability of process visualizations because templates may be created by graphic experts independently from specific visualization demands. The feasibility of our concept is demonstrated by a prototypical implementation.

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Copy reference link   DOI: 10.1109/SOCA.2012.6449464

Abstract: Business analysts want to monitor the status of their business goals in a business-centric manner, without any knowledge of the actual implementation artifacts that contribute to achieve these goals. Business transactions are one means to represent business goals and requirements. A business transaction is typically implemented by a choreography of different parties contributing to the accomplishment of a common agreement. To meet the constantly changing requirements for all parties in a business transaction choreographies often have to be adapted (e.g. based on the capabilities of different execution environments). The resulting challenge is that the execution state of a choreography executed on several locations has to be propagated to the business analyst to enable monitoring of the (adapted) business transaction. For this purpose we introduce a meta-model and state model of business transactions. Based on these models, we introduce a two-stage monitoring approach involving state propagation of the execution status of the adapted choreography to the original choreography and from there to the business transaction.

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