KWM: Knowledge-based Workflow Model for agile organization

The workflow management system (WFMS) in an agile organization should be highly adaptable to the frequent organizational changes. To increase the adaptability of contemporary WFMSs, a mechanism for managing changes within the organizational structure and changes in business rules needs to be reinforced. In this paper, a knowledge-based approach for workflow modeling is proposed, in which a workflow is defined as a set of business rules. Knowledge on the organizational structure and special workflow, such as role/actor mappings and complex routing rules, can be explicitly modeled in KWM (Knowledge-based Workflow Model). Using knowledge representation scheme and dependency management facility, a change propagation mechanism is provided to adapt to the frequent changes in the organizational structure, business rules, and procedures

Управляемые тупики в параллельных ресурсно-ограниченных потоках работ

We study the verification of the soundness property for workflow nets extended with resources. A workflow is sound if it terminates properly (no deadlocks and livelocks are possible). A class of resource-constrained workflow nets (RCWF-nets) is considered, where resources can be used by a process instance, but cannot be created or spent. Two sound RCWF-nets using the same set of resources can be put in parallel. This parallel composition may in some cases produce additional deadlocks. A problem of deadlock avoidance in parallel workflows is studied, some methods of deadlock search and control are presented.Работа посвящена проблеме проверки правильной организованности (бездефектности) сетей потоков работ с ресурсами. Поток работ называется бездефектным, если он может быть корректно завершен от любого достижимого состояния. Рассматривается класс схем ресурсно-ограниченных потоков работ (RCWF-сетей), в которых экземпляры процесса могут использовать внешние ресурсы, но не могут за время своей жизни изменить их количество.Две бездефектные RCWF-сети, использующие один и тот же набор ресурсов, могут быть запущены параллельно. Подобная параллельная композиция в некоторых случаях может порождать дополнительные тупики, вызванные взаимными блокировками. Мы исследуем проблему обнаружения потенциальных блокировок и предлагаем способы организации такого управления сетью, которое позволило бы их избегать

Soundness of workflow nets : classification, decidability, and analysis

Workflow nets, a particular class of Petri nets, have become one of the standard ways to model and analyze workflows. Typically, they are used as an abstraction of the workflow that is used to check the so-called soundness property. This property guarantees the absence of livelocks, deadlocks, and other anomalies that can be detected without domain knowledge. Several authors have proposed alternative notions of soundness and have suggested to use more expressive languages, e.g., models with cancellations or priorities. This paper provides an overview of the different notions of soundness and investigates these in the presence of different extensions of workflow nets. We will show that the eight soundness notions described in the literature are decidable for workflow nets. However, most extensions will make all of these notions undecidable. These new results show the theoretical limits of workflow verification. Moreover, we discuss some of the analysis approaches described in the literature

Complexity of the soundness problem of bounded workflow nets

Classical workflow nets (WF-nets) are an important class of Petri nets that are widely used to model and analyze workflow systems. Soundness is a crucial property that guarantees these systems are deadlock-free and bounded. Aalst et al. proved that the soundness problem is decidable, and proposed (but not proved) that the soundness problem is EXPSPACE-hard. In this paper, we show that the satisfiability problem of Boolean expression is polynomial time reducible to the liveness problem of bounded WF-nets, and soundness and liveness are equivalent for bounded WF-nets. As a result, the soundness problem of bounded WF-nets is co-NP-hard. Workflow nets with reset arcs (reWF-nets) are an extension to WF-nets, which enhance the expressiveness of WF-nets. Aalst et al. proved that the soundness problem of reWF-nets is undecidable. In this paper, we show that for bounded reWF-nets, the soundness problem is decidable and equivalent to the liveness problem. Furthermore, a bounded reWF-net can be constructed in polynomial time for every linear bounded automaton (LBA) with an input string, and we prove that the LBA accepts the input string if and only if the constructed reWF-net is live. As a result, the soundness problem of bounded reWF-nets is PSPACE-hard.No Full Tex

Complexity of the soundness problem of workflow nets

Classical workflow nets (WF-nets for short) are an important subclass of Petri nets that are widely used to model and analyze workflow systems. Soundness is a crucial property of workflow systems and guarantees that these systems are deadlock-free and bounded. Aalst et al. proved that the soundness problem is decidable for WF-nets and can be polynomially solvable for free-choice WF-nets. This paper proves that the soundness problem is PSPACE-hard for WF-nets. Furthermore, it is proven that the soundness problem is PSPACE-complete for bounded WF-nets. Based on the above conclusion, it is derived that the soundness problem is also PSPACE-complete for bounded WF-nets with reset or inhibitor arcs (ReWF-nets and InWF-nets for short, resp.). ReWF- and InWF-nets are two extensions to WF-nets and their soundness problems were proven by Aalst et al. to be undecidable. Additionally, we prove that the soundness problem is co-NP-hard for asymmetric-choice WF-nets that are a larger class and can model more cases of interaction and resource allocation than free-choice ones.No Full Tex

Verification of priced and timed extensions of Petri Nets with multile instances

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Sistemas Informáticos y Computación, leída el 25-01-2016Las redes de Petri son un lenguaje formal muy adecuado para la modelizacíon, ańalisis y verificacíon de sistemas concurrentes con infinitos estados. En particular, son muy apropiadas para estudiar las propiedades de seguridad de dichos sistemas, dadas sus buenas propiedades de decidibilidad. Sin embargo, en muchas ocasiones las redes de Petri carecen de la expresividad necesaria para representar algunas caracteŕısticas fundamentales de los sistemas que se manejan hoy en d́ıa, como el manejo de tiempo real, costes reales, o la presencia de varios procesos con un ńumero no acotado de estados ejecut́andose en paralelo. En la literatura se han definido y estudiado algunas extensiones de las redes de Petri para la representaci ́on de las caracteŕısticas anteriores. Por ejemplo, las “Redes de Petri Temporizadas” [83, 10](TPN) incluyen el manejo de tiempo real y las ν-redes de Petri [78](ν-PN) son capaces de representar un ńumero no acotado de procesos con infinitos estados ejecut́andose concurrentemente. En esta tesis definimos varias extensiones que réunen estas dos caracteŕısticas y estudiamos sus propiedades de decidibilidad. En primer lugar definimos las “ν-Redes de Petri Temporizadas”, que réunen las caracteŕısticas expresivas de las TPN y las ν-PN. Este nuevo modelo es capaz de representar sistemas con un ńumero no acotado de procesos o instancias, donde cada proceso es representado por un nombre diferente, y tiene un ńumero no acotado de relojes reales. En este modelo un reloj de una instancia debe satisfacer ciertas condiciones (pertenecer a un intervalo dado) para formar parte en el disparo de una transicíon. Desafortunadamente, demostramos que la verificacíon de propiedades de seguridad es indecidible para este modelo...The model of Petri nets is a formal modeling language which is very suitable for the analysis and verification of infinite-state concurrent systems. In particular, due to its good decidability properties, it is very appropriate to study safety properties over such systems. However, Petri nets frequently lack the expressiveness to represent several essential characteristics of nowadays systems such as real time, real costs, or the managing of several parallel processes, each with an unbounded number of states. Several extensions of Petri nets have been defined and studied in the literature to fix these shortcomings. For example, Timed Petri nets [83, 10] deal with real time and ν-Petri nets [78] are able to represent an unbounded number of different infinite-state processes running concurrently. In this thesis we define new extensions which encompass these two characteristics, and study their decidability properties. First, we define Timed ν-Petri nets by joining together Timed Petri nets and ν-Petri nets. The new model represents systems in which each process (also called instance) is represented by a different pure name, and it is endowed with an unbounded number of clocks. Then, a clock of an instance must satisfy certain given conditions (belonging to a given interval) in order to take part in the firing of a transition. Unfortunately, we prove that the verification of safety properties is undecidable for this model. In fact, it is undecidable even if we only consider two clocks per process. We restrict this model and define Locally-Synchronous ν-Petri nets by considering only one clock per instance, and successfully prove the decidability of safety properties for this model. Moreover, we study the expressiveness of Locally-Synchronous ν-Petri nets and prove that it is the most expressive non Turing-complete extension of Petri nets with respect to the languages they accept...Depto. de Sistemas Informáticos y ComputaciónFac. de InformáticaTRUEunpu

A modular approach to the specification and management of time duration constraints in BPMN

The modeling and management of business processes deals with temporal aspects both in the inherent representation of activity coordination and in the specification of activity properties and constraints. In this paper, we address the modeling and specification of constraints related to the duration of process activities. In detail, we consider the Business Process Model and Notation (BPMN) standard and propose an approach to define re-usable duration-aware process models that make use of existing BPMN elements for representing different nuances of activity duration at design time. Moreover, we show how advanced event-handling techniques may be exploited for detecting the violation of duration constraints during the process run-time. The set of process models specified in this paper suitably captures duration constraints at different levels of abstraction, by allowing designers to specify the duration of atomic tasks and of selected process regions in a way that is conceptually and semantically BPMN-compliant. Without loss of generality, we refer to real-world clinical working environments to exemplify our approach, as their intrinsic complexity makes them a particularly challenging and rewarding application environment

Knowledge based approach to flexible workflow management systems

This thesis was submitted for the degree of Doctor of Philosophy and awarded the Korea Advanced Institute of Science and Technology (KAIST).Today's business environments are characterized by dynamic and uncertain environments. In order to effectively support business processes in such contexts, workflow management systems must be able to adapt themselves effectively. In this dissertation, the workflow is redefined in concept and represented with a set of business rules. Business rules play a central role in organizational workflows in context of cooperation among actors. To achieve business goals, they constrain the flow of works, use of resources, and responsibility mapping between tasks and actors using role concept. Business rules are explicitly modeled in the Knowledge-based Workflow Model (KWM) using frames. To increase the adaptability of workflow management system, KWM has several distinctive features. First, it increases expressiveness of workflow model so that exception handling rules and responsibility mapping rules between tasks and actors as well as task scheduling rules are explicitly modeled. Secondly, formal definition of KWM enables one to define and to analyze correctness of workflow schema. Knowledge-based approach enables more powerful analysis on workflow schema including checking consistency and compactness of routing rules as well as terminality of a workflow. Thirdly, providing change propagation mechanism which assures correctness of workflow after the modification of workflow schema increases adaptability. Change propagation rules for the modification primitives are provided to manage workflow evolution. On the other hand, metarules that control rules in KWM are used to handle exceptions that occur in a running workflow instance. Workflow participants can easily change workflow schema of a workflow instance with the support of extra rules and a metarule. Based on KWM, K-WFMS (Knowledge-based WorkFlow Management System) has been implemented in client/server architecture. Inference shell of knowledge-based systems is employed for enactment of business rules and integrated with database systems. From a real application based on the KWM architecture, it has been shown that system performance can increase notably by reducing the number of rules and facts that are used in the course of workflow enactment

Obstructions in Security-Aware Business Processes

This Open Access book explores the dilemma-like stalemate between security and regulatory compliance in business processes on the one hand and business continuity and governance on the other. The growing number of regulations, e.g., on information security, data protection, or privacy, implemented in increasingly digitized businesses can have an obstructive effect on the automated execution of business processes. Such security-related obstructions can particularly occur when an access control-based implementation of regulations blocks the execution of business processes. By handling obstructions, security in business processes is supposed to be improved. For this, the book presents a framework that allows the comprehensive analysis, detection, and handling of obstructions in a security-sensitive way. Thereby, methods based on common organizational security policies, process models, and logs are proposed. The Petri net-based modeling and related semantic and language-based research, as well as the analysis of event data and machine learning methods finally lead to the development of algorithms and experiments that can detect and resolve obstructions and are reproducible with the provided software