Modeling multimedia workflow patterns using Dynamic Petri Nets and Orc
01 Oct 2007-Vol. 1, pp 73-80
TL;DR: This paper addresses the modeling of complex workflow patterns and proposes a new approach able to both represent complex distributed multimedia presentation using dynamic petri nets (DPNs) and to translate a verified set of specifications into the new deterministic programming language Orc.
Abstract: In distributed multimedia presentation systems, a workflow is defined to specify which activities need to be executed and in which order. Workflows need to be modeled and verified for effective synchronisation during playout. To model several of these workflows, high-level petri nets have been commonly used. However, petri nets are not suitable for distributed applications and most of them are limited in their capability in modeling workflows having multiple instances with or without a priori runtime knowledge. In this paper, we address the modeling of complex workflow patterns and propose a new approach able to both represent complex distributed multimedia presentation using dynamic petri nets(DPNs) and to translate a verified set of specifications into the new deterministic programming language Orc. DPNs are programmable petri nets that can: efficiently model user interactions and synchronised iterative playouts, and ensure that they represent consistent presentations, while Orc allows providing easy implementations using a set of powerful constructs.
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01 Dec 2014
TL;DR: This paper proposes an efficient context-aware open e-learning environment to do the same to author and deliver courses for diverse learners with varied backgrounds dynamically.
Abstract: With the explosive growth in the World Wide Web over the past few decades, a predominant part of the pedagogical arena is making a transition from stereotype textbook learning to massive open online learning. Efforts are being made to develop and foster crowd sourced massive open repositories of learning objects, which can be tapped to author courses for diverse learners with varied backgrounds dynamically. Developing systems to author and deliver such courses has been of rising importance to contemporary researchers and this paper proposes an efficient context-aware open e-learning environment to do the same. The learning objects having high aptness to the particular course and high content-based predicted rating pertaining to the particular learner's preferences are picked from the open repository and the course structure is modeled using communicating dynamic Petri nets. Ratings and feedback from the user are obtained during presentation, based on which the course delivery is made adaptive. Rating prediction through Collaborative filtering is used for this purpose. The ratings are also used to implicitly learn the learner's preferences and to establish an aptness score for each learning object.
2 citations
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01 May 1997
TL;DR: An overview of the design and structure of the verifier, its theoretical foundation, and an overview of significant practical applications are given.
Abstract: SPIN is an efficient verification system for models of distributed software systems. It has been used to detect design errors in applications ranging from high-level descriptions of distributed algorithms to detailed code for controlling telephone exchanges. The paper gives an overview of the design and structure of the verifier, reviews its theoretical foundation, and gives an overview of significant practical applications.
4,159 citations
TL;DR: This paper introduces workflow management as an application domain for Petri nets, presents state-of-the-art results with respect to the verification of workflows, and highlights some Petri-net-based workflow tools.
Abstract: Workflow management promises a new solution to an age-old problem: controlling, monitoring, optimizing and supporting business processes. What is new about workflow management is the explicit representation of the business process logic which allows for computerized support. This paper discusses the use of Petri nets in the context of workflow management. Petri nets are an established tool for modeling and analyzing processes. On the one hand, Petri nets can be used as a design language for the specification of complex workflows. On the other hand, Petri net theory provides for powerful analysis techniques which can be used to verify the correctness of workflow procedures. This paper introduces workflow management as an application domain for Petri nets, presents state-of-the-art results with respect to the verification of workflows, and highlights some Petri-net-based workflow tools.
2,862 citations
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01 Jul 2003
TL;DR: In this paper, the authors describe a number of workflow patterns addressing what they believe identify comprehensive workflow functionality and provide the basis for an in-depth comparison of commercial workflow management systems.
Abstract: Differences in features supported by the various contemporary commercial workflow management systems point to different insights of suitability and different levels of expressive power. The challenge, which we undertake in this paper, is to systematically address workflow requirements, from basic to complex. Many of the more complex requirements identified, recur quite frequently in the analysis phases of workflow projects, however their implementation is uncertain in current products. Requirements for workflow languages are indicated through workflow patterns. In this context, patterns address business requirements in an imperative workflow style expression, but are removed from specific workflow languages. The paper describes a number of workflow patterns addressing what we believe identify comprehensive workflow functionality. These patterns provide the basis for an in-depth comparison of a number of commercially available workflow management systems. As such, this paper can be seen as the academic response to evaluations made by prestigious consulting companies. Typically, these evaluations hardly consider the workflow modeling language and routing capabilities, and focus more on the purely technical and commercial aspects.
2,553 citations
TL;DR: A novel approach, called Orc for orchestration, that supports a structured model of concurrent and distributed programming that assumes that basic services, like sequential computation and data manipulation, are implemented by primitive sites.
Abstract: W ee xplore the following quintessential problem: gi ven as et o fb asic computing elements how do we compose them to yield interesting computation patterns. Our goa li s to study composition operators which apply across a broad spec- trum of computing elements, from sequential programs to distributed transac- tions over computer networks. Our theory makes ver yf ew assumptions about the nature of the basi ce lements; in particular, we do not assume that an ele- ment's computation always terminates, or that it is deterministic. We develop a theory which provides useful guidance for application designs, from integration of sequential programs to coordination of distributed tasks. The primary appli- cation of interest for us is orchestration of web services over the internet, which we describe in detail in this paper.
226 citations
TL;DR: It is concluded that Petri nets cannot model workflows accurately, unless they are extended with a syntax and semantics for reactivity, whereas the semantics of UMLact ivity diagrams models open, reactive systems.
Abstract: Petri net variants are widely used as a workflow modelling technique. Recently, UMLa ctivity diagrams have been used for the same purpose, even though the syntax and semantics of activity diagrams has not been yet fully worked out. Nevertheless, activity diagrams seem very similar to Petri nets and on the surface, one may think that they are variants of each other. To substantiate or deny this claim, we need to formalise the intended semantics of activity diagrams and then compare this with various Petri net semantics. In previous papers we have defined two formal semantics for UMLact ivity diagrams that are intended for workflow modelling. In this paper, we discuss the design choices that underlie these two semantics and investigate whether these design choices can be met in low-level and high-level Petri net semantics. We argue that the main difference between the Petri net semantics and our semantics of UML act ivity diagrams is that the Petri net semantics models resource usage of closed, active systems that are non-reactive, whereas our semantics of UMLact ivity diagrams models open, reactive systems. Since workflow systems are open, reactive systems, we conclude that Petri nets cannot model workflows accurately, unless they are extended with a syntax and semantics for reactivity.
93 citations