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Realizability Is Controllability [chapter]

Niels Lohmann, Karsten Wolf
2010 Lecture Notes in Computer Science  
A choreography describes the interaction between services. It may be used for specification purposes, for instance serving as a contract in the design of an interorganizational business process. Typically, not all describable interactions make sense which motivates the study of the realizability problem for a given choreography. In this paper, we show that realizability can be traced back to the problem of controllability which askes whether a service has compatible partner processes. This way
more » ... rocesses. This way of thinking makes algorithms for controllability available for reasoning about realizability. In addition, it suggests alternative definitions for realizability. We discuss several proposals for defining realizability which differ in the degree of coverage of the specified interaction.
doi:10.1007/978-3-642-14458-5_7 fatcat:ijl5wxkg7zhnfe6gmiq64ajqw4

Artifact-Centric Choreographies [chapter]

Niels Lohmann, Karsten Wolf
2010 Lecture Notes in Computer Science  
Classical notations for service collaborations focus either on the control flow of participating services (interacting models) or the order in which messages are exchanged (interaction models). None of these approaches emphasizes the evolution of data involved in the collaboration. In contrast, artifact-centric models pursue the converse strategy and begin with a specification of data objects. This paper extends existing concepts for artifact-centric business process models with the concepts of
more » ... ith the concepts of agents and locations. By making explicit who is accessing an artifact and where the artifact is located, we are able to automatically generate an interaction model that can serve as a contract between the agents and by construction makes sure that specified global goal states on the involved artifacts are reached. The derivation of the interaction model is solely based on existing methods and tools [18, 24, 20, 19] . Local policies of the involved agents can easily be incorporated. Models using a single artifact hub appear as a special case in our approach where there is only a single agent. In a setting with more than one agent, however, our approach reaches beyond the single agent setting: We derive not only the actions that need to be performed on the artifacts for reaching a goal but also the messages that need to be exchanged between agents for this purpose. The paper is organized as follows. The next section briefly describes how artifacts can be modeled with Petri nets. Section 3 introduces location-aware extensions and their impact to artifact models. Section 4 provides a categorization of location information which may serve as suggestion for a high-level language for location-aware artifacts. The construction of an interaction model out of location-aware artifacts is described in Sect. 5. Section 6 shows our approach in the context of related work before Sect. 7 concludes and discusses several possible extensions to the work of this paper.
doi:10.1007/978-3-642-17358-5_3 fatcat:p7frplrd6fcazp6v7p3i6utp5q

Artifact-Centric Modeling Using BPMN [chapter]

Niels Lohmann, Martin Nyolt
2012 Lecture Notes in Computer Science  
BPMN offers a rich pool of language constructs to model different aspects of choreographies, interorganizational business processes and service compositions. With collaborations and choreographies, BPMN enables the modeler concentrate on the control flow and the message flow, respectively. At the same time, data flow is only treated as a subordinate extension. In contrast, recent artifact-centric approaches model processes from the point of view of the data objects that are manipulated during
more » ... anipulated during the process. This paper investigates to what extend BPMN is suitable to model artifact-centric processes and which extensions are required to comfortably support this modeling approach.
doi:10.1007/978-3-642-31875-7_7 fatcat:jkarjtfbhzagtf6wgm6565lt3y

Where Did I Go Wrong? [chapter]

Niels Lohmann, Dirk Fahland
2014 Lecture Notes in Computer Science  
Soundness Security Compliance Conformance to ... diagnostic information verification technique domain-specific high-quality -moving target -domain-specific approaches too specific to follow Verification of processes and services 5 CMMN Declare WS-BPEL WS-Policy EPC BPMN YAWL Object Life-Cycles GSM Rules Soundness Security Compliance Conformance to ... diagnostic information verification technique high-quality general purpose
doi:10.1007/978-3-319-10172-9_18 fatcat:ljwin32lm5atdmoq5pdejq6n4i

Decidability Results for Choreography Realization [chapter]

Niels Lohmann, Karsten Wolf
2011 Lecture Notes in Computer Science  
A service choreography defines a set of permitted sequences of message events as a specification for the interaction of services. Realizability is a fundamental sanity check for choreographies comparable to the notion of soundness for workflows. We study several notions of realizability: partial, distributed, and complete realizability. They establish increasingly strict conditions on realizing services. We investigate decidability issues under the synchronous and asynchronous communication
more » ... s communication models. For partial realizability, we show undecidability whereas the other two problems are decidable with reasonable complexity.
doi:10.1007/978-3-642-25535-9_7 fatcat:4ddk3o4a5bgr3boiyq5wjcqm4i

Compliance by design for artifact-centric business processes

Niels Lohmann
2013 Information Systems  
Compliance to legal regulations, internal policies, or best practices is becoming a more and more important aspect in business processes management. Compliance requirements are usually formulated in a set of rules that can be checked during or after the execution of the business process, called compliance by detection. If noncompliant behavior is detected, the business process needs to be redesigned. Alternatively, the rules can be already taken into account while modeling the business process
more » ... e business process to result in a business process that is compliant by design. This technique has the advantage that a subsequent verification of compliance is not required. This paper focuses on compliance by design and employs an artifactcentric approach. In this school of thought, business processes are not described as a sequence of tasks to be performed (i. e., imperatively), but from the point of view of the artifacts that are manipulated during the process (i. e., declaratively). We extend the artifact-centric approach to model compliance rules and show how compliant business processes can be synthesized automatically.
doi:10.1016/j.is.2012.07.003 fatcat:4b2dwkra7vbs3c327vu33g6kgy

Analyzing Interacting BPEL Processes [chapter]

Niels Lohmann, Peter Massuthe, Christian Stahl, Daniela Weinberg
2006 Lecture Notes in Computer Science  
This paper addresses the problem of analyzing the interaction between BPEL processes. We present a technology chain that starts out with a BPEL process and transforms it into a Petri net model. On the model we decide controllability of the process (the existence of a partner process, such that both can interact properly) and compute its operating guideline (a characterization of all properly interacting partner processes). A case study demonstrates the value of this technology chain.
doi:10.1007/11841760_3 fatcat:reer4tek5ffjvkyrdiy5ah53wq

Non-desynchronizable Service Choreographies [chapter]

Gero Decker, Alistair Barros, Frank Michael Kraft, Niels Lohmann
2008 Lecture Notes in Computer Science  
A precise definition of interaction behavior between services is a prerequisite for successful business-to-business integration. Service choreographies provide a view on message exchanges and their ordering constraints from a global perspective. Assuming message sending and receiving as one atomic step allows to reduce the modelers' effort. As downside, problematic race conditions resulting in deadlocks might appear when realizing the choreography using services that exchange messages
more » ... messages asynchronously. This paper presents typical issues when desynchronizing service choreographies. Solutions from practice are discussed and a formal approach based on Petri nets is introduced for identifying desynchronizable choreographies.
doi:10.1007/978-3-540-89652-4_26 fatcat:wupw3gob7veujccyqzcefjycsq

Automatic Test Case Generation for Interacting Services [chapter]

Kathrin Kaschner, Niels Lohmann
2009 Lecture Notes in Computer Science  
Niels Lohmann is funded by the DFG project "Operating Guidelines for Services" (WO 1466/8-1).  ... 
doi:10.1007/978-3-642-01247-1_7 fatcat:tbfr6mkd75bkxpqko64lyqp27q

Asymmetric collaboration in virtual reality

Lui Albæk Thomsen, Niels Christian Nilsson, Rolf Nordahl, Boris Lohmann
2019 Læring og Medier  
It has been established that Virtual Reality (VR) possesses certain qualities for educational purposes. These include the ability to place the learner at the location or in the perspective that the desired knowledge exists (e.g., travelling to another planet or shrinking to miniature size to observe internal anatomy). VR is also considered to contribute with enriching the curricular content, promoting active forms of learning, performance assessment of high validity, and provide the opportunity
more » ... ide the opportunity to teach applied academic knowledge in life-like situations. In regards to teaching mathematics and geometry, three key affordances have been identified; interactive manipulation and construction of three-dimensional geometry, comprehension of spatial relationships, and rectification of abstract problems. Safety protocols and practical guidelines from classroom experimentation have also been formulated by various research projects. In this manuscript, asymmetrical immersive VR in education will be reviewed, as it is relevant for the narrative of learning situations where multiple students use the technology together. As an example, in mathematics, asymmetric VR could be used in contexts where unknown variables must be found in collaboration. The purpose of the narrative literature review is to gain a greater understanding of how asymmetric game mechanics has influence on communication and collaboration between learners. To map the dynamics of this type of learning activity, a taxonomy will be presented. Since VR is still under development in terms of hardware and software, it is important that the current and future technical possibilities are described in a conceptual manner, as well as conclude on optimal coupling between communication dynamics and collaboration mechanics.
doi:10.7146/lom.v12i20.109391 fatcat:t5t3bew5ovcblepkzvow7vayly

Compliance by Design for Artifact-Centric Business Processes [chapter]

Niels Lohmann
2011 Lecture Notes in Computer Science  
Compliance to legal regulations, internal policies, or best practices is becoming a more and more important aspect in business processes management. Compliance requirements are usually formulated in a set of rules that can be checked during or after the execution of the business process, called compliance by detection. If noncompliant behavior is detected, the business process needs to be redesigned. Alternatively, the rules can be already taken into account while modeling the business process
more » ... e business process to result in a business process that is compliant by design. This technique has the advantage that a subsequent verification of compliance is not required. This paper focuses on compliance by design and employs an artifactcentric approach. In this school of thought, business processes are not described as a sequence of tasks to be performed (i. e., imperatively), but from the point of view of the artifacts that are manipulated during the process (i. e., declaratively). We extend the artifact-centric approach to model compliance rules and show how compliant business processes can be synthesized automatically.
doi:10.1007/978-3-642-23059-2_11 fatcat:72ku3rstpzd73fm7uaz7lwyqti

Modeling Wizard for Confidential Business Processes [chapter]

Andreas Lehmann, Niels Lohmann
2013 Lecture Notes in Business Information Processing  
A core motivation of service-oriented execution of business processes is the opportunity to reduce costs by outsourcing certain tasks to third-party service providers. For legal or economic reasons, it might be undesirable that delicate information (e. g., customer data, trade secrets, or financial details) "leak" to the involved third parties. The absence of such leaks -called noninterference -can be checked automatically. To this end, a model is required in which each task is assessed as
more » ... is assessed as either confidential or public. A drawback of this method is that (1) this distinction has to be made for each task prior to the verification and that (2) an unsuccessful check requires a new confidentiality assessment followed by another verification step. This paper introduces a full-automatic technique to complete partial confidentiality assessments while guaranteeing noninterference. The proposed technique can be integrated into the design phase of a service-oriented business process and help the modeler choose which tasks can be safely outsourced.
doi:10.1007/978-3-642-36285-9_67 fatcat:4j3jqwfbmbd6vpdivrlhdm2vte

Another Approach to Service Instance Migration [chapter]

Nannette Liske, Niels Lohmann, Christian Stahl, Karsten Wolf
2009 Lecture Notes in Computer Science  
Acknowledgements Niels Lohmann and Karsten Wolf are funded by the DFG project "Operating Guidelines for Services" (WO 1466/8-1).  ... 
doi:10.1007/978-3-642-10383-4_44 fatcat:swm6q6npqbhp7ejnts3nifkrqy

Stubborn Sets for Simple Linear Time Properties [chapter]

Andreas Lehmann, Niels Lohmann, Karsten Wolf
2012 Lecture Notes in Computer Science  
We call a linear time property simple if counterexamples are accepted by a Büchi automaton that has only singleton strongly connected components. This class contains interesting properties such as LTL formulas G(ϕ =⇒ F ψ) or ϕ U ψ which have not yet received support beyond general LTL preserving approaches. We contribute a stubborn set approach to simple properties with the following ingredients. First, we decompose the verification problem into finitely many simpler problems that can be
more » ... that can be independently executed. Second, we propose a stubborn set method for the resulting problems that does neither require cycle detection, nor stuttering invariance, nor existence of transitions that are invisible to all atomic propositions. This means that our approach is applicable in cases where traditional approaches fail. Third, we show that sufficient potential is left in existing implementations of the proposed conditions by exploiting all the available nondeterminism in these procedures. We employ a translation to integer linear programming (ILP) for supporting this claim.
doi:10.1007/978-3-642-31131-4_13 fatcat:ssedfndrjjfqfamglpqem54ffa

Petri Net Transformations for Business Processes – A Survey [chapter]

Niels Lohmann, Eric Verbeek, Remco Dijkman
2009 Lecture Notes in Computer Science  
In Process-Aware Information Systems, business processes are often modeled in an explicit way. Roughly speaking, the available business process modeling languages can be divided into two groups. Languages from the first group are preferred by academic people but shunned by business people, and include Petri nets and process algebras. These academic languages have a proper formal semantics, which allows the corresponding academic models to be verified in a formal way. Languages from the second
more » ... s from the second group are preferred by business people but disliked by academic people, and include BPEL, BPMN, and EPCs. These business languages often lack any proper semantics, which often leads to debates on how to interpret certain business models. Nevertheless, business models are used in practice, whereas academic models are hardly used. To be able to use, for example, the abundance of Petri net verification techniques on business models, we need to be able to transform these models to Petri nets. In this paper, we investigate a number of Petri net transformations that already exist. For every transformation, we investigate the transformation itself, the constructs in the business models that are problematic for the transformation and the main applications for the transformation.
doi:10.1007/978-3-642-00899-3_3 fatcat:kohig2pkkfh7zoch4gq6tnjbdm
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