Browsing by Author "Leymann, Frank"

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Open Access
Abschlussbericht des Verbundprojekts Tools4BPEL
(2009) Iron, Rolf; Kopp, Oliver; Leiner, Andreas; Leymann, Frank; Massuthe, Peter
Unternehmensübergreifende Geschäftsprozesse werden zunehmend nach dem Paradigma der Services organisiert. Dabei stellen sich Fragen nach der Komponierbarkeit, Fehlerbehandlung, sowie der Rücksetzbarkeit (Kompensation) im Fehlerfall. In diesem Vorhaben werden Methoden und Werkzeuge zum Umgang mit solchen Fragen entwickelt und am Beispiel der Geschäftsprozess-Modellierungssprache BPEL und im Modellierungswerkzeug der Firma MEGA international erprobt. Es wurde zum einen der Übersetzer BPEL2oWFN entwickelt, der anhand einer Petrinetzsemantik für BPEL einen BPEL-Prozess in ein (offenes) Petrinetz transformiert. Zum anderen wurden Korrektheitskriterien (wie Bedienbarkeit und Verhaltenskompatibilität) für Services erarbeitet, Algorithmen zu ihrer Überprüfung entworfen und in Fiona implementiert. Die Algorithmen sind Petrinetz-basiert. Damit spielen Übersetzung und Analyse eng zusammen und ein vorhandener BPEL-Prozess kann auf bspw. Bedienbarkeit hin untersucht werden. In diesem Vorhaben wurden die Modellierungssprache BPEL4Chor, Choreographie-Erweiterungen für BPMN entwickelt, sowie die Transformation von BPMN nach BPEL angepasst, um den Weg von BPMN nach BPEL4Chor zu unterstützen. Weiterhin wurden Konzepte entwickelt, wie sich partner-übergreifende Fehlerbehandlung, Rücksetzbarkeit, sowie die Autonomie der Partner mittels BPEL4Chor darstellen lassen. BPEL4Chor kann als Standardsprache zur Spezifikation von Protokollen, die zwischen mehreren Partnern ablaufen, verwendet werden. Durch seine enge Verbindung mit BPEL kann BPEL4Chor sehr gut als Startpunkt für eine Webservice-Lösung verwendet werden.
Open Access
Abstract syntax of WS-BPEL 2.0
(2008) Kopp, Oliver; Mietzner, Ralph; Leymann, Frank
WS-BPEL 2.0 is the current version of the "Business Process Execution Language for Web Services". Until now, no formal definition of its syntax exists. We present a complete syntax of WS-BPEL 2.0 of both abstract and executable processes.
Open Access
Automated quantum hardware selection for quantum workflows
(2021) Weder, Benjamin; Barzen, Johanna; Leymann, Frank; Salm, Marie
The execution of a quantum algorithm typically requires various classical pre- and post-processing tasks. Hence, workflows are a promising means to orchestrate these tasks, benefiting from their reliability, robustness, and features, such as transactional processing. However, the implementations of the tasks may be very heterogeneous and they depend on the quantum hardware used to execute the quantum circuits of the algorithm. Additionally, today’s quantum computers are still restricted, which limits the size of the quantum circuits that can be executed. As the circuit size often depends on the input data of the algorithm, the selection of quantum hardware to execute a quantum circuit must be done at workflow runtime. However, modeling all possible alternative tasks would clutter the workflow model and require its adaptation whenever a new quantum computer or software tool is released. To overcome this problem, we introduce an approach to automatically select suitable quantum hardware for the execution of quantum circuits in workflows. Furthermore, it enables the dynamic adaptation of the workflows, depending on the selection at runtime based on reusable workflow fragments. We validate our approach with a prototypical implementation and a case study demonstrating the hardware selection for Simon’s algorithm.
Open Access
Configurable readout error mitigation in quantum workflows
(2022) Beisel, Martin; Barzen, Johanna; Leymann, Frank; Truger, Felix; Weder, Benjamin; Yussupov, Vladimir
Current quantum computers are still error-prone, with measurement errors being one of the factors limiting the scalability of quantum devices. To reduce their impact, a variety of readout error mitigation methods, mostly relying on classical post-processing, have been developed. However, the application of these methods is complicated by their heterogeneity and a lack of information regarding their functionality, configuration, and integration. To facilitate their use, we provide an overview of existing methods, and evaluate general and method-specific configuration options. Quantum applications comprise many classical pre- and post-processing tasks, including readout error mitigation. Automation can facilitate the execution of these often complex tasks, as their manual execution is time-consuming and error-prone. Workflow technology is a promising candidate for the orchestration of heterogeneous tasks, offering advantages such as reliability, robustness, and monitoring capabilities. In this paper, we present an approach to abstractly model quantum workflows comprising configurable readout error mitigation tasks. Based on the method configuration, these workflows can then be automatically refined into executable workflow models. To validate the feasibility of our approach, we provide a prototypical implementation and demonstrate it in a case study from the quantum humanities domain.
Open Access
Continued fractions and probability estimations in Shor’s algorithm : a detailed and self-contained treatise
(2022) Barzen, Johanna; Leymann, Frank
Shor’s algorithm for prime factorization is a hybrid algorithm consisting of a quantum part and a classical part. The main focus of the classical part is a continued fraction analysis. The presentation of this is often short, pointing to text books on number theory. In this contribution, we present the relevant results and proofs from the theory of continued fractions in detail (even in more detail than in text books), filling the gap to allow a complete comprehension of Shor’s algorithm. Similarly, we provide a detailed computation of the estimation of the probability that convergents will provide the period required for determining a prime factor.
Open Access
Coordination protocols for split BPEL loops and scopes
(2007) Khalaf, Rania; Leymann, Frank
The document presents an approach to enable loops and fault handling, compensating scopes to be split among a set of BPEL processes running on different BPEL engines. A mechanism to split a scope or loop into multiple fragments is presented, then a protocol is defined that can be used to coordinate fragments of a loop or a scope so that those fragments run as if they had been in a single process. The requirements for running split scopes and loops are explained. For compensation, this paper focuses on explicit compensation and makes the assumption that compensation handing does not fail. Two protocols are defined such that they may be plugged into the WS-Coordination framework. The messages between the participant fragments and the coordinator are defined. The information about the participating processes that the coordinator needs to have is specified. An algorithm is provided to locate a fault handler in the hierarchy of scopes that can handle a particular BPEL fault. Additionally, the behavior of both participants and the coordinator are specified.
Open Access
An event model for WS-BPEL 2.0
(2011) Kopp, Oliver; Henke, Sebastian; Karastoyanova, Dimka; Khalaf, Rania; Leymann, Frank; Sonntag, Mirko; Steinmetz, Thomas; Unger, Tobias; Wetzstein, Branimir
This report presents an engine-independent WS-BPEL 2.0 event model. It supports both passive monitoring and active control of process execution by external applications. Some of the assumptions in the presented event model are inspired by a particular implementation, e.g. fault handling and compensation; however they are kept as general as possible, so that they can be mapped on other engine-specific approaches to tackle faults and support compensation. In addition, the report draws on the experience of some of the authors in business process management and software development. The overall BPEL event model consists of a set of event models for the different types of BPEL entities that change their states: processes, process instances, general activities, scope activities, invoke activities, loops, links, variables, partner links, and correlation sets. The event model is used by the authors of the report in several projects, all utilizing process life cycle events in different scenarios.
Open Access
An integrated management system for composed applications deployed by different deployment automation technologies
(2023) Harzenetter, Lukas; Breitenbücher, Uwe; Binz, Tobias; Leymann, Frank
Automation is the key to enable an efficient, fast, and reliable deployment of applications. Therefore, several deployment automation technologies emerged in recent years whereby each technology has its specific field of application: While some are bound to cloud providers and offer provider-specific functionalities, others enable multi-cloud deployments but mostly do not support provider-specific features. As a consequence, often companies have to use multiple deployment technologies in combination to deploy large applications. However, the management capabilities of most deployment technologies are limited or even non-existent. This issue becomes even more severe if different parts of a single application are deployed by different technologies. To tackle this issue, we present an approach that enables generating automatically executable management workflows for applications that consist of multiple components deployed by different deployment technologies. Our approach builds on top of instance models that are automatically generated based on information retrieved from the different deployment technologies involved. Based on the derived instance model, we generate workflows that manipulate the running application. We prove the technical feasibility by an open-source prototype and discuss a detailed case study.
Open Access
A language-agnostic framework for the analysis of the syntactic structure of process fragments
(2010) Mancioppi, Michele; Danylevych, Olha; Papazoglou, Mike P.; Leymann, Frank
Process fragments are a cornerstone of process modeling in both Service Oriented Architecture and Business Process Management. The state of the art lacks shared, language agnostic definitions of the basic concepts and properties of process fragments. This absence of a common foundation for the research on process fragments hinders the comparison and reuse of the results in the state of the art, and renders impossible the reaching of agreed, intensional definitions of the different typologies of process fragments. The present work aims at filling this gap by providing a framework of language agnostic definitions of properties of the syntactic structure of process fragments based on the mereotopology of discrete space. Alongside familiar mereologic concepts like inclusion, overlap and disjointness, we cover fundamental concepts for process fragments like (dis)connection, selfconnectedness, borders, interiors and exteriors. Besides providing a foundation for further research on process fragments, we discuss the immediate application of the concepts defined in this work in the scope of the change management of process models.
Open Access
Modeling different deployment variants of a composite application in a single declarative deployment model
(2022) Stötzner, Miles; Becker, Steffen; Breitenbücher, Uwe; Képes, Kálmán; Leymann, Frank
For automating the deployment of composite applications, typically, declarative deployment models are used. Depending on the context, the deployment of an application has to fulfill different requirements, such as costs and elasticity. As a consequence, one and the same application, i.e., its components, and their dependencies, often need to be deployed in different variants. If each different variant of a deployment is described using an individual deployment model, it quickly results in a large number of models, which are error prone to maintain. Deployment technologies, such as Terraform or Ansible, support conditional components and dependencies which allow modeling different deployment variants of a composite application in a single deployment model. However, there are deployment technologies, such as TOSCA and Docker Compose, which do not support such conditional elements. To address this, we extend the Essential Deployment Metamodel (EDMM) by conditional components and dependencies. EDMM is a declarative deployment model which can be mapped to several deployment technologies including Terraform, Ansible, TOSCA, and Docker Compose. Preprocessing such an extended model, i.e., conditional elements are evaluated and either preserved or removed, generates an EDMM conform model. As a result, conditional elements can be integrated on top of existing deployment technologies that are unaware of such concepts. We evaluate this by implementing a preprocessor for TOSCA, called OpenTOSCA Vintner, which employs the open-source TOSCA orchestrators xOpera and Unfurl to execute the generated TOSCA conform models.
Open Access
Propagation of states from BPEL process instances to Chevron models
(2011) Schumm, David; Karastoyanova, Dimka; Leymann, Frank; Lie, Sumadi
This report describes key aspects of a code library that we developed for the purpose of state propagation for business process monitoring on different levels of abstraction. The library supports the propagation of execution states of process instances based on the Business Process Execution Language (BPEL) to process models specified in the "Chevron" language. The Chevron language is an abstract, non-executable process language that we especially designed for abstract process instance monitoring purposes. The look and feel of this graphical language is similar to value chains. The basic concept of the Chevron language is based on Chevron-shaped charts which can be modeled in Microsoft PowerPoint to describe a process on a high level of abstraction. We aim at enabling the use of high-level process in order to monitor the instance status of a much more detailed, lower-level model. We describe the overall procedure of performing state projections along a concrete scenario. We describe a format for state propagation rules which define how the status of activities of a BPEL process instance should be projected to the elements of a Chevron model. We present a format to serialize process models in the Chevron language. We present a graphical template based on Scalable Vector Graphics (SVG) which we employ to render a stateful Chevron model graphically. The Chevron language is just one language to be used for abstract representation of process instances. However, the approach for state propagation is generic and can be applied for other languages, too.
Open Access
A prototype for view-based monitoring of BPEL processes
(2011) Schumm, David; Latuske, Gregor; Leymann, Frank
This report describes the initial version of a tool for business process monitoring based on process viewing techniques. The tool, Business Process Illustrator (BPI), has been developed in the course of a Diploma Thesis which has been conducted at the Institute of Architecture of Application Systems. BPI is a Web-based tool for monitoring the execution of business processes. It displays the current state of a process instance in form of a process graph which is refreshed regularly. The initial version of the prototype supports regular process monitoring of processes based on the Business Process Execution Language (BPEL), plus process view transformations to reduce complexity and to ease analysis of process instances.
Open Access
Provenance-preserving analysis and rewrite of quantum workflows for hybrid quantum algorithms
(2023) Weder, Benjamin; Barzen, Johanna; Beisel, Martin; Leymann, Frank
Quantum applications are hybrid, i.e., they comprise quantum and classical programs, which must be orchestrated. Workflows are a proven solution for orchestrating heterogeneous programs while providing benefits, such as robustness or scalability. However, the orchestration using workflows can be inefficient for some quantum algorithms, requiring the execution of quantum and classical programs in a loop. Hybrid runtimes are offered to efficiently execute these algorithms. For this, the quantum and classical programs are combined in a single hybrid program, for which the execution is optimized. However, this leads to a conceptual gap between the modeling benefits of workflow technologies, e.g., modularization, reuse, and understandability, and the efficiency improvements when using hybrid runtimes. To close this gap, we introduce a method to model all tasks explicitly in the workflow model and analyze the workflow to detect parts of the workflow that can benefit from hybrid runtimes. Furthermore, corresponding hybrid programs are automatically generated based on the quantum and classical programs, and the workflow is rewritten to invoke them. To ease the live monitoring and later analysis of workflow executions, we integrate process views into our method and collect related provenance data. Thus, the user can visualize and monitor the workflow in the original and rewritten form within the workflow engine. The practical feasibility of our approach is validated by a prototypical implementation, a case study, and a runtime evaluation.
Open Access
Realizing enterprise integration patterns in WebSphere
(2005) Scheibler, Thorsten; Leymann, Frank
Over the last few years, patterns became focus of many activities in both, software development and research. Because of the financial significance of enterprise application integration (EAI) technologies corresponding patterns in this area are especially important and, thus, found a lot of interest. Even a standard textbook has been well-established in this space ("Enterprise Integration Patterns"). People are asking for guidelines about how to use the patterns from this textbook in their environment. A Whitepaper of Hohpe provides a sample integration scenario together with guidelines of how to implement this integration scenario based on a subset of the patterns in the BizTalk Server 2004 environment. In this document, we use the same scenario and the same patterns as in this Whitepapper and show how to implement them in WebSphere.
Open Access
Selection and optimization of hyperparameters in warm-started quantum optimization for the MaxCut problem
(2022) Truger, Felix; Beisel, Martin; Barzen, Johanna; Leymann, Frank; Yussupov, Vladimir
Today’s quantum computers are limited in their capabilities, e.g., the size of executable quantum circuits. The Quantum Approximate Optimization Algorithm (QAOA) addresses these limitations and is, therefore, a promising candidate for achieving a near-term quantum advantage. Warm-starting can further improve QAOA by utilizing classically pre-computed approximations to achieve better solutions at a small circuit depth. However, warm-starting requirements often depend on the quantum algorithm and problem at hand. Warm-started QAOA (WS-QAOA) requires developers to understand how to select approach-specific hyperparameter values that tune the embedding of classically pre-computed approximations. In this paper, we address the problem of hyperparameter selection in WS-QAOA for the maximum cut problem using the classical Goemans-Williamson algorithm for pre-computations. The contributions of this work are as follows: We implement and run a set of experiments to determine how different hyperparameter settings influence the solution quality. In particular, we (i) analyze how the regularization parameter that tunes the bias of the warm-started quantum algorithm towards the pre-computed solution can be selected and optimized, (ii) compare three distinct optimization strategies, and (iii) evaluate five objective functions for the classical optimization, two of which we introduce specifically for our scenario. The experimental results provide insights on efficient selection of the regularization parameter, optimization strategy, and objective function and, thus, support developers in setting up one of the central algorithms of contemporary and near-term quantum computing.
Open Access
Space-based computing and semantics : a web service purist's point of view
(2006) Leymann, Frank
We review the concept of space-based computing and its combination with semantics into triple-space computing. Comparing this concept with existing technology we conclude that applying triple-spaces to Web service technology does not result into something fundamentally new to the architecture of Web services: we argue that this is an application of the concepts of binding and discovery which in contrast are fundamental aspects of the architecture of Web services.
Open Access
WS-BPEL extension for compliance fragments (BPEL4CFrags), Version 1.0
(2011) Görlach, Katharina; Kopp, Oliver; Leymann, Frank; Schumm, David; Strauch, Steve
The Web Services Business Process Execution Language, version 2.0 (WS-BPEL 2.0 or BPEL for brevity) introduces a model for business processes based on Web services. A BPEL process orchestrates interactions among different Web services. The language comprises features required to describe complex control flows, including error handling and compensation behaviour. BPEL for Compliance Fragments (BPEL4CFrags) enables the specification of compliance fragments providing a reusable solution for implementing and meeting compliance requirements. The compliance fragments are not necessarily executable. Providing process modeling support at design time requires the completion of not directly executable compliance fragments, because compliance fragments contain several degrees of freedom, into already existing executable BPEL processes. Moreover, assistance for creation of executable BPEL processes from scratch during IT refinement has to be provided.
Open Access
WS-BPEL extension for semantic web services (BPEL4SWS), version 1.0
(2008) Karastoyanova, Dimka; Van Lessen, Tammo; Leymann, Frank; Nitzsche, Joerg; Wutke, Daniel
The Web Services Business Process Execution Language, version 2.0 (WS-BPEL 2.0 or BPEL for brevity) introduces a model for business processes based on Web services. A BPEL process orchestrates interactions among different Web services. The language encompasses features needed to describe complex control flows, including error handling and compensation behavior. BPEL for Semantic Web Services (BPEL4SWS) uses Semantic Web Service Frameworks to define a communication channel between two partner services instead of using the partner link which is based on WSDL 1.1. It enables describing activity implementations in a much more flexible manner based on ontological descriptions of service requesters and providers.