Mixing Paradigms for More Comprehensible Models

Petri nets efficiently model both data- and control-flow. Control-flow is either modeled explicitly as flow of a specific kind of data, or implicit based on the data-flow. Explicit modeling of control-flow is useful for well-known and highly structured processes, but may make modeling of abstract features of models, or processes which are highly dynamic, overly complex. Declarative modeling, such as is supported by Declare and DCR graphs, focus on control-flow, but does not specify it explicitly; instead specifications come in the form of constraints on the order or appearance of tasks. In this paper we propose a combination of the two, using colored Petri nets instead of plain Petri nets to provide full data support. The combined approach makes it possible to add a focus on data to declarative languages, and to remove focus from the explicit control-flow from Petri nets for dynamic or abstract processes. In addition to enriching both procedural processes in the form of Petri nets and declarative processes, we also support a flow from modeling only abstract data- and control-flow of a model towards a more explicit control-flow model if so desired. We define our combined approach, and provide considerations necessary for enactment. Our approach has been implemented in CPN Tools 4

Data driven nets: a maximally concurrent, procedural, parallel process representation for distributed control systems

technical reportA procedural parallel process representation, known as data-driven nets is described. The sequencing mechanism of the data-driven representation is based on the principle of data dependency. Operations are driven into action by the arrival of the required working set of input operands. Execution of DDN processes is side-effect free, and influence in the net representation is transparaent. Data-driven nets have several advantages over many of the existing parallel process representations. These nets are capable of representing parallelism below the statement level, and in addition may be arbitrarily pipelined. Data-driven nets are simpler than other data-flow schema in that no distinction need be made between control and data. A process model for data-driven nets is given and a number of properties of the model are discussed. The operating rules for data-driven nets are completely asynchronous and the nets therefore serve as an excellent low-level process notation for distributed systems

Algebraic High-Level Nets and Processes Applied to Communication Platforms

Petri nets are well-known to model communication structures and algebraic specifications for modeling data types. Algebraic High-Level (AHL) nets are defined as integration of Petri nets with algebraic data types, which allows to model the communication structure and the data flow within one modelling framework. Transformations of AHL-nets – inspired by the theory of graph transformations – allow in addition to modify the communication structure. Moreover, highlevel processes of AHL-nets capture the concurrent semantics of AHL-nets in an adequate way. Altogether we obtain a powerful integrated formal specification technique to model and analyse all kinds of communication based systems. In this paper we give a comprehensive introduction of this framework. This includes main results concerning parallel independence of AHL-transformations and the transformation and amalgamation of AHL-occurrence nets and processes. Moreover, we show how this can be applied to model and analyse modern communication and collaboration platforms like Google Wave and Wikis. Especially we show how the Local Church-Rosser theorem for AHL-net tranformations can be applied to ensure the consistent integration of different platform evolutions. Moreover, the amalgamation theorem for AHL-processes shows under which conditions we can amalgamate waves of different Google Wave platforms in a compositional way

Modelling Evolution of Communication Platforms and Scenarios based on Transformations of High-Level Nets and Processes : Extended Version

Algebraic High-Level (AHL) nets are a well-known modelling technique based on Petri nets with algebraic data types, which allows to model the communication structure and the data flow within one modelling framework. Transformations of AHL-nets – inspired by the theory of graph transformations – allow in addition to modify the communication structure. Moreover, high-level processes of AHL-nets capture the concurrent semantics of AHL-nets in an adequate way. Altogether we obtain a powerful integrated formal specification technique to model and analyse all kinds of communication based systems, especially different kinds of communication platforms. In this paper we show how to model the evolution of communication platforms and scenarios based on transformations of Algebraic High-Level Nets and Processes. All constructions and results are illustrated by a running example showing the evolution of Apache Wave platforms and scenarios. The evolution of platforms is modelled by the transformation of AHL-nets and that of scenarios by the transformation of AHL-net processes. The first main result shows under which conditions AHL-net processes can be extended if the corresponding AHL-net is transformed. This result can be applied to show the extension of scenarios for a given platform evolution. The second main result shows how AHL-net processes can be transformed based on a special kind of transformation for AHL-nets, corresponding to action evolution of platforms. Finally, we briefly discuss the case of multiple action evolutions

Transforming nested structures of flowchart into hierarchical coloured Petri Nets

Flowchart is commonly used diagram to represent the processes in design phase of a software system. However, the flowchart of a complex software system inevitably contains the nested structures of branching and looping of the processes. The verification of these nested structure of the flowchart in advance is still difficult to conduct even using simulation techniques. In this paper, we intend to consider the complex flowchart with nested structures, so called nested-if and nested-loop, as our input design model. A set of mapping rules is proposed to transform the input complex flowchart with nested structures into the hierarchical coloured Petri nets to avoid the drawing of a single huge net of complicate model. The hierarchical coloured Petri nets also provides us to manage level of abstraction of the formal model and helps us concentrate on only an appropriate detail at a time. In our transforming approach, both data flow and control flow of the processes in flowchart are concerned as well so that all changing states of the observable variables in the flowchart would be represented and simulated in our resulting hierarchical coloured Petri nets. The CPN simulation tool is used to test and ensure the correctness of our resulting hierarchical coloured Petri nets

Development of a coupling algorithm for fluid-structure interaction analysis of submerged aquaculture nets

A coupling algorithm between two open-source numerical toolboxes, i.e., OpenFOAM and Code_Aster, is implemented for fluid-structure interaction analysis of submerged nets. This algorithm is developed to handle the wake effects of thin, flexible and highly permeable structures with complex geometries. Compared to previous approaches, the present algorithm simplifies the procedures of the model preparation by removing additional data-fitting processes for porous coefficients, and improves the accuracy of structural responses by employing a fluid solver to calculate the flow field and a superior Screen model to calculate the hydrodynamic forces. The coupling algorithm is comprehensively described and validated with published experiments for both fixed and flexible nets. Different solidities, inflow angles, incoming velocities and dimensions of nets are also considered. The comparisons of flow velocity in the wake, deformation of flexible nets and drag force on the full-scale fish cage show that the numerical results obtained from the present coupling algorithm are in good agreement with published experimental data.publishedVersio

Responsible Composition and Optimization of Integration Processes under Correctness Preserving Guarantees

Enterprise Application Integration deals with the problem of connecting heterogeneous applications, and is the centerpiece of current on-premise, cloud and device integration scenarios. For integration scenarios, structurally correct composition of patterns into processes and improvements of integration processes are crucial. In order to achieve this, we formalize compositions of integration patterns based on their characteristics, and describe optimization strategies that help to reduce the model complexity, and improve the process execution efficiency using design time techniques. Using the formalism of timed DB-nets - a refinement of Petri nets - we model integration logic features such as control- and data flow, transactional data storage, compensation and exception handling, and time aspects that are present in reoccurring solutions as separate integration patterns. We then propose a realization of optimization strategies using graph rewriting, and prove that the optimizations we consider preserve both structural and functional correctness. We evaluate the improvements on a real-world catalog of pattern compositions, containing over 900 integration processes, and illustrate the correctness properties in case studies based on two of these processes.Comment: 37 page

NiMoToons: a totally graphic workbench for program tuning and experimentation

NiMo (Nets In Motion) is a Graphic-Functional-Data Flow language designed to visualize algorithms and their execution in an understandable way. Programs are process networks that evolve showing the full state at each execution step. Processes are polymorphic, higher order and have multiple outputs. The language has a set of primitive processes well suited for stream programming and supports open programs and interactive debugging. The new version of the environment NiMo Toons includes: an also graphic and incremental type inference system, multiple output processes as higher order parameters, symbolic execution, five evaluation modes that can be globally or locally set for each process and dynamically changed, and facilities to measure the used resources (parallelism level, number of steps, number of processes, etc.)Postprint (author’s final draft

Learning Spatiotemporal Features for Infrared Action Recognition with 3D Convolutional Neural Networks

Infrared (IR) imaging has the potential to enable more robust action recognition systems compared to visible spectrum cameras due to lower sensitivity to lighting conditions and appearance variability. While the action recognition task on videos collected from visible spectrum imaging has received much attention, action recognition in IR videos is significantly less explored. Our objective is to exploit imaging data in this modality for the action recognition task. In this work, we propose a novel two-stream 3D convolutional neural network (CNN) architecture by introducing the discriminative code layer and the corresponding discriminative code loss function. The proposed network processes IR image and the IR-based optical flow field sequences. We pretrain the 3D CNN model on the visible spectrum Sports-1M action dataset and finetune it on the Infrared Action Recognition (InfAR) dataset. To our best knowledge, this is the first application of the 3D CNN to action recognition in the IR domain. We conduct an elaborate analysis of different fusion schemes (weighted average, single and double-layer neural nets) applied to different 3D CNN outputs. Experimental results demonstrate that our approach can achieve state-of-the-art average precision (AP) performances on the InfAR dataset: (1) the proposed two-stream 3D CNN achieves the best reported 77.5% AP, and (2) our 3D CNN model applied to the optical flow fields achieves the best reported single stream 75.42% AP

Verification of soundness and other properties of business processes

In this thesis we focus on improving current modeling and verification techniques for complex business processes. The objective of the thesis is to consider several aspects of real-life business processes and give specific solutions to cope with their complexity. In particular, we address verification of a proper termination property for workflows, called generalized soundness. We give a new decision procedure for generalized soundness that improves the original decision procedure. The new decision procedure reports on the decidability status of generalized soundness and returns a counterexample in case the workflow net is not generalized sound. We report on experimental results obtained with the prototype implementation we made and describe how to verify large workflows compositionally, using reduction rules. Next, we concentrate on modeling and verification of adaptive workflows — workflows that are able to change their structure at runtime, for instance when some exceptional events occur. In order to model the exception handling properly and allow structural changes of the system in a modular way, we introduce a new class of nets, called adaptive workflow nets. Adaptive workflow nets are a special type of Nets in Nets and they allow for creation, deletion and transformation of net tokens at runtime and for two types of synchronizations: synchronization on proper termination and synchronization on exception. We define some behavioral properties of adaptive workflow nets: soundness and circumspectness and employ an abstraction to reduce the verification of these properties to the verification of behavioral properties of a finite state abstraction. Further, we study how formal methods can help in understanding and designing business processes. We investigate this for the extended event-driven process chains (eEPCs), a popular industrial business process language used in the ARIS Toolset. Several semantics have been proposed for EPCs. However, most of them concentrated solely on the control flow. We argue that other aspects of business processes must also be taken into account in order to analyze eEPCs and propose a semantics that takes data and time information from eEPCs into account. Moreover, we provide a translation of eEPCs to Timed Colored Petri nets in order to facilitate verification of eEPCs. Finally, we discuss modeling issues for business processes whose behavior may depend on the previous behavior of the process, history which is recorded by workflow management systems as a log. To increase the precision of models with respect to modeling choices depending on the process history, we introduce history-dependent guards. The obtained business processes are called historydependent processes.We introduce a logic, called LogLogics for the specification of guards based on a log of a current running process and give an evaluation algorithm for such guards. Moreover, we show how these guards can be used in practice and define LogLogics patterns for properties that occur most commonly in practice