The architecture of discovery net : towards grid-based discovery services

Imperial Users onl

Performance analysis and optimization for workflow authorization

Many workflow management systems have been developed to enhance the performance of workflow executions. The authorization policies deployed in the system may restrict the task executions. The common authorization constraints include role constraints, Separation of Duty (SoD), Binding of Duty (BoD) and temporal constraints. This paper presents the methods to check the feasibility of these constraints, and also determines the time durations when the temporal constraints will not impose negative impact on performance. Further, this paper presents an optimal authorization method, which is optimal in the sense that it can minimize a workflow’s delay caused by the temporal constraints. The authorization analysis methods are also extended to analyze the stochastic workflows, in which the tasks’ execution times are not known exactly, but follow certain probability distributions. Simulation experiments have been conducted to verify the effectiveness of the proposed authorization methods. The experimental results show that comparing with the intuitive authorization method, the optimal authorization method can reduce the delay caused by the authorization constraints and consequently reduce the workflows’ response time

Optimizing performance of workflow executions under authorization control

“Business processes or workflows are often used to model enterprise or scientific applications. It has received considerable attention to automate workflow executions on computing resources. However, many workflow scenarios still involve human activities and consist of a mixture of human tasks and computing tasks. Human involvement introduces security and authorization concerns, requiring restrictions on who is allowed to perform which tasks at what time. Role- Based Access Control (RBAC) is a popular authorization mechanism. In RBAC, the authorization concepts such as roles and permissions are defined, and various authorization constraints are supported, including separation of duty, temporal constraints, etc. Under RBAC, users are assigned to certain roles, while the roles are associated with prescribed permissions. When we assess resource capacities, or evaluate the performance of workflow executions on supporting platforms, it is often assumed that when a task is allocated to a resource, the resource will accept the task and start the execution once a processor becomes available. However, when the authorization policies are taken into account,” this assumption may not be true and the situation becomes more complex. For example, when a task arrives, a valid and activated role has to be assigned to a task before the task can start execution. The deployed authorization constraints may delay the workflow execution due to the roles’ availability, or other restrictions on the role assignments, which will consequently have negative impact on application performance. When the authorization constraints are present to restrict the workflow executions, it entails new research issues that have not been studied yet in conventional workflow management. This thesis aims to investigate these new research issues. First, it is important to know whether a feasible authorization solution can be found to enable the executions of all tasks in a workflow, i.e., check the feasibility of the deployed authorization constraints. This thesis studies the issue of the feasibility checking and models the feasibility checking problem as a constraints satisfaction problem. Second, it is useful to know when the performance of workflow executions will not be affected by the given authorization constraints. This thesis proposes the methods to determine the time durations when the given authorization constraints do not have impact. Third, when the authorization constraints do have the performance impact, how can we quantitatively analyse and determine the impact? When there are multiple choices to assign the roles to the tasks, will different choices lead to the different performance impact? If so, can we find an optimal way to conduct the task-role assignments so that the performance impact is minimized? This thesis proposes the method to analyze the delay caused by the authorization constraints if the workflow arrives beyond the non-impact time duration calculated above. Through the analysis of the delay, we realize that the authorization method, i.e., the method to select the roles to assign to the tasks affects the length of the delay caused by the authorization constraints. Based on this finding, we propose an optimal authorization method, called the Global Authorization Aware (GAA) method. Fourth, a key reason why authorization constraints may have impact on performance is because the authorization control directs the tasks to some particular roles. Then how to determine the level of workload directed to each role given a set of authorization constraints? This thesis conducts the theoretical analysis about how the authorization constraints direct the workload to the roles, and proposes the methods to calculate the arriving rate of the requests directed to each role under the role, temporal and cardinality constraints. Finally, the amount of resources allocated to support each individual role may have impact on the execution performance of the workflows. Therefore, it is desired to develop the strategies to determine the adequate amount of resources when the authorization control is present in the system. This thesis presents the methods to allocate the appropriate quantity for resources, including both human resources and computing resources. Different features of human resources and computing resources are taken into account. For human resources, the objective is to maximize the performance subject to the budgets to hire the human resources, while for computing resources, the strategy aims to allocate adequate amount of computing resources to meet the QoS requirements

Managing quality constraints in technology-managed learning content processes

Technology-enhanced learning content processes consist of individual activities related to the creation, composition, consumption and analysis of content facilitated through services. These service processes are often enacted across different boundaries such as organisations, countries or even languages. Specifically, looking at the quality of learning content and other artefacts and the governance of respective processed through services in this context is important to control quality requirements. We assume a partially automated workflow process for the content lifecycle. We suggest a rule-based constraints monitoring of learning content processes. A learning domain ontology shall capture the key data/content types, activities and constraints, which forms the basis of a rule-based policy monitoring solution that takes content provenance data into account

Security Mechanisms for Workflows in Service-Oriented Architectures

Die Arbeit untersucht, wie sich Unterstützung für Sicherheit und Identitätsmanagement in ein Workflow-Management-System integrieren lässt. Basierend auf einer Anforderungsanalyse anhand eines Beispiels aus der beruflichen Weiterbildung und einem Abgleich mit dem Stand der Technik wird eine Architektur für die sichere Ausführung von Workflows und die Integration mit Identitätsmanagement-Systemen entwickelt, die neue Anwendungen mit verbesserter Sicherheit und Privatsphäre ermöglicht

Dynamic Authorisation Policies for Event-based Task Delegation

International audienceTask delegation presents one of the business process security leitmotifs. It denes a mechanism that bridges the gap between both workfow and access control systems. There are two important issues relating to delegation, namely allowing task delegation to complete, and having a secure delegation within a workfow. Delegation completion and authorisation enforcement are specied under specic constraints. Constraints are dened from the delegation context implying the presence of a xed set of delegation events to control the delegation execution. In this paper, we aim to reason about delegation events to specify delegation policies dynamically. To that end, we present an event-based task delegation model to monitor the delegation process. We then identify relevant events for authorisation enforcement to specify delegation policies. Moreover, we propose a technique that automates delegation policies using event calculus to control the delegation execution and increase the compliance of all delegation changes in the global policy

A logical framework for reasoning about delegation policies in workflow management systems

International audienceTask delegation presents one of the business process security leitmotifs. It defines a mechanism that bridges the gap between workflow and access control systems. Delegation completion and authorisation enforcement are specified under specific constraints so-called events. In this article, we aim to reason about delegation events to model task delegation and to specify delegation policies using a logical framework. To that end, we propose an event-based task delegation model to control the delegation execution. We then identify relevant events responsible for the dynamic enforcement of delegation policies. Further, we define a task-oriented access control model to specify delegation constraints into authorisation policies. Finally, we propose a technique to automate the delegation policies integration. Using event calculus, we develop a reasoning tool to control the delegation execution and to increase the compliance of all delegation changes in the existing policy of the workflow