Decomposition-Based Verification of Cyclic Workflows

A Formal Classification of Process Anomalies for Workflow Verification

Grid workflows are becoming a mainstream paradigm for implementing complex grid applications. In addition to existing grid enabling techniques, various grid ensuring techniques are emerging, e.g. workflow analysis and temporal reasoning, to probe potential pitfalls and errors and guarantee quality of services (QoS) at a design phase. A new state p calculus is proposed in this work, which not only enables flexible abstraction and management of historical grid system events, but also facilitates modeling and verification of grid workflows. Some typical patterns in grid workflows are captured and both static and dynamic formal verification issues are investigated, including structural correctness, specification satisfiability, logic satisfiability and consistency. A grid workflow modeling and verification environment, GridPiAnalyzer, is implemented using formal modeling and verification methods proposed in this work. Performance evaluation results are included using a grid workflow for gravitational wave data analysis.

Petri nets are frequently used for the modeling and analysis of workflows. Their graphical nature, well-defined semantics, and analysis techniques are attractive as information systems become more process-aware. Unfortunately, the classical Petri net has problems modeling cancellation in a succinct and direct manner. Modeling cancellation regions in a classical net is impossible or results in a spaghetti-like net. Cancellation regions are supported by many workflow management systems, but these systems do not support advanced analysis techniques (process mining, verification, performance analysis, etc.). This paper proposes to use reset workflow nets(RWF-nets) and discusses (1) the discoveryof RWF-nets (i.e., extracting information from event logs to construct such models), (2) the verificationof RWF-nets (i.e., checking whether a workflow process has deadlocks, livelocks, etc.), and (3) the conformanceof an event log with respect to a RWF-net (i.e., comparing real with modeled behavior).

Recently, a significant body of research has been dedicated to the analysis and verification of workflows without taking into account the temporal dimension of activities involved. Workflow also has a strong temporal aspect: activity sequencing, deadlines, routing conditions, and scheduling all involve the element of time. Once the temporal aspects of the activities in a process description are taken into account, various types of synchronization anomalies and other undesirable behavior may be detected. In this article, we address both the quantitative temporal aspect and the qualitative temporal aspect of workflow systems. On one hand, based on time Petri net (TPN), we introduce a set of linear inference algorithms to solve some quantitative inference problems of temporal constraints of workflows. On the other hand, based on extended interval temporal logic (EITL), we propose temporal logic workflow models to qualitatively infer temporal relations among tasks of workflow systems. © 2004 Wiley Periodicals, Inc.

Workflow systems coordinate tasks of humans and computers. The iTask system is a recently developed toolkit with which workflows can be defined declaratively on a very high level of abstraction. It offers functionality which cannot be found in commercial workflow systems: workflows are constructed dynamically depending on the outcome of earlier work, workflows are strongly typed, and they can be of higher order. From the specification, a web-based multi-user workflow system is generated. Up until now we could only generate thin clients. All information produced by a worker triggers a round trip to the server. For real world workflows this is unsatisfactory. Modern Ajax web technology to update part of a web page is required, as well as the ability to execute tasks on clients. The architecture of any system that supports such features is complex: it manages distributed computing on clients and server which generally involves the collaboration of applications written in different programming languages. The contribution of this paper is that we integrate partial updates of web pages and client side task evaluation within the iTask system, while retaining its approach of a single language and declarative nature. The workflow designer uses light-weight annotations to control the run-time behavior of work. The iTask implementation takes care of all the hard work under the hood. Arbitrary tasks (functional programs) can be evaluated at web clients. When such a task cannot be evaluated on the client for some reason, the system switches to server side evaluation. All communication and synchronization issues are handled by the extended iTask system

The workflow management of incident command systems (ICSs) has been challenged by the systems' special requirements on flexibility, intuitiveness, and capacity of correctness verification. The significance of applying formal approaches to the modeling and analysis of workflows has been well recognized, and many such approaches have been proposed. However, these approaches require users to master considerable knowledge of the particular formalisms, which impacts the application of these approaches on a larger scale. This paper presents a new formal, yet intuitive, approach for the modeling and analysis of workflows, which attempts to overcome the aforementioned problem. In addition to the abilities of supporting workflow validation and enactment, this new approach possesses the distinguishing feature of allowing users who are not proficient in formal methods to build up and dynamically modify the workflow models that address the flexibility needs of ICSs.

Clinical Pathways can be viewed as workflows, comprising an ordering of activities with associated execution constraints. Workflow models allow formal representation, analysis and execution of workflows in the Clinical Pathways. We present a semantic web-based approach where the domain knowledge and the workflow model are modeled separately as ontologies, while the Clinical Pathway and the associated workflows are modeled as the instantiations of these ontologies. Our workflow model is based on the UML Activity Diagrams and OWL-S service ontology, and the execution semantics are based on Place/Transition Petri Nets. We demonstrate our approach by capturing the workflow of the Prostate Cancer Care Pathway.

Workflow technology has become a standard solution for managing increasingly complex business processes. Successful business process management depends on effective workflow modeling and analysis. One of the important aspects of workflow analysis is the data-flow perspective because, given a syntactically correct process sequence, errors can still occur during workflow execution due to incorrect data-flow specifications. However, there have been only scant treatments of the data-flow perspective in the literature and no formal methodologies are available for systematically discovering data-flow errors in a workflow model. As an indication of this research gap, existing commercial workflow management systems do not provide tools for data-flow analysis at design time. In this paper, we provide a data-flow perspective for detecting data-flow anomalies such as missing data, redundant data, and potential data conflicts. Our data-flow framework includes two basic components: data-flow specification and data-flow analysis; these components add more analytical rigor to business process management.

A Model Slicing Method for Workflow Verification

In these lecture notes we present the iTasks system: a set of combinators to specify work flows in a pure functional language at a very high level of abstraction. Work flow systems are automated systems in which tasks are coordinated that have to be executed by either humans or computers. The combinators that we propose support work flow patterns commonly found in commercial work flow systems. In addition, we introduce novel work flow patterns that capture real world requirements, but that can not be dealt with by current systems. Compared with most of these commercial systems, the iTasks system offers several further advantages: tasks are statically typed, tasks can be higher order, the combinators are fully compositional, dynamic and recursive work flows can be specified, and last but not least, the specification is used to generate an executable web-based multi-user work flow application. With the iTasks system, useful work flows can be defined which cannot be expressed in other systems: a work can be interrupted and subsequently directed to other workers for further processing. The iTasks system has been constructed in the programming language Clean, making use of its generic programming facilities, and its iData toolkit with which interactive, thin-client, form-based web applications can be created. In all, iTasks are an excellent case of the expressive power of functional and generic programming.

Businesses face significant obstacles during their interaction with public administrations and governments, having to cope with bureaucracy and ambiguous procedures, a fact that makes e-government a necessity today. Inherent complexity of the e-government application domain is also reflected in the workflows of e-government service provision. This paper reports on how some real examples of e-government service workflows were modelled in a simple and structured fashion by recognising and re-using recurring segments. At the same time, we present our course of work which can be used as a light framework for refining workflows, identifying, building and binding workflow blocks that are reusable and render the workflow modelling easier, faster and less prone to errors. Such an approach, drawing from current workflow modelling trends, presents important potential to facilitate e-government workflow modelling by enabling systematic and rapid design of new service workflows.

Faulty device drivers are a major source of operating system failures. We argue that the underlying cause of many driver faults is the separation of two highly-related tasks: device verification and driver development. These two tasks have a lot in common, and result in software that is conceptually and functionally similar, yet kept totally separate. The result is a particularly bad case of duplication of effort: the verification code is correct, but is discarded after the device has been manufactured; the driver code is inferior, but used in actual device operation. We claim that the two tasks, and the software they produce, can and should be unified, and this will result in drastic improvement of device-driver quality and reduction in the development cost and time to market.In this paper we propose a device driver design and verification workflow that achieves such unification. We apply this workflow to develop and test drivers for four different I/O devices and demonstrate that it improves the driver test coverage and allows detecting driver defects that are extremely hard to find using conventional testing techniques.

This paper presents a holistic approach to the realisation of Privacy by Design in workflow environments, ensuring that workflow models are rendered privacy-aware already at their specification phase. In this direction, the proposed framework, considering the particular technical requirements stemming from data protection principles, is centred around the following features: a novel, ontology-based approach to workflow modelling, which manages, unlike all other existing technologies, to adequately capture privacy aspects pertaining to workflow execution; the appropriate codification of privacy requirements into compliance rules and directives; an automated procedure for the verification of workflow models and their subsequent transformation, if needed, so that they become inherently privacy-aware before being deployed for execution.

Design and Verification of Time-Constrained Workflows With Multi-Level Security

Data-oriented workflows are often used in scientific applications for executing a set of dependent tasks across multiple computers. We discuss how these can be modeled using lambda calculus, and how ideas from functional programming are applicable in the design of workflows. Such an approach avoids the restrictions often found in workflow languages, permitting the implementation of complex application logic and data manipulation. This paper explains why lambda calculus is an appropriate model for workflow representation, and how a suitably efficient implementation can provide a wide range of capabilities to developers. The presented approach also permits high-level workflow features to be implemented at user level, in terms of a small set of low-level primitives provided by the language implementation.