Sea Ling

Time Petri nets for workflow modelling and analysis

Time management in workflow processes is crucial in determining and controlling the life cycle of business activities. In our model, a temporal interval as an execution duration is assigned to every workflow task. While the real time taken by the task is nondeterministic and unpredictable, it may be between the bounds thus specified. We extend workflow nets (WF-nets) with time intervals and call the new nets Time WF-nets (TWF-nets). Extending our previous results on timed Petri nets, we show that certain behavioural properties of workflow processes modelled in TWF-nets can be verified. Using a clinical health care process as a case study, we also illustrate the modelling of shared resources available at different times.

Describing Web Service Architectures through Design-by-Contract

Architectural description languages (ADLs) are used to specify a high-level, compositional view of a software application, specifying how a system is to be composed from coarse-grain components. ADLs usually come equipped with a formal dynamic semantics, facilitating specification and analysis of distributed and event-based systems. In this paper, we describe the Radl [12], an ADL framework that provides both a process and a structural view of web service-based systems. We use Petri-net descriptions to give a dynamic view of business workflow for web service collaboration. We adapt the approach of [14] to define a form of design-by-contract [10] for configuring workflow architectures. This serves as a configuration-level means of constructing safer, more robust systems.

A survey on context-aware workflow adaptations

Recently, workflow has been employed in pervasive computing systems to orchestrate and provide services to the users. Since pervasive computing systems emphasise context-awareness and adaptability, these two features must be included in the workflow mechanism in order to utilise workflow in pervasive environment. In this paper we present various existing approaches to adaptation in context-aware workflow. These approaches are compared based on the common adaptation characteristics identified from our study. Lastly, we discuss and point out the future challenges of predictive adaptation for context-aware workflows.

An adaptive mediation framework for mobile p2p social content sharing

Mobile Social Network in Proximity (MSNP) represents a new form of social network in which users are capable of interacting with their surroundings via their mobile devices in public mobile peer-to-peer (MP2P) environments. MSNP brings opportunity to people to meet new friends, share device content, and perform various social activities. However, as the fundamental topology of MSNP is based on public MP2P network, many challenges have arisen. Existing related works restrict the MP2P social network to operate in specific platforms and protocols. Enabling MSNP in a dynamic public MP2P requires a more flexible solution, which can adapt its behaviour to comply with environment. Hence, we propose a mobile device-hosted service-oriented workflow-based mediation framework for MSNP. The fundamental portion of the framework is based on the Enterprise Service Bus architecture which supports changes in runtime resources without the need to re-launch the application. In order to adapt to different situations, our workflow tasks adjust the execution behaviour at runtime. The workflow engine dynamically selects the best approach to complete the mobile users request based on the cost and performance, calculated by combining fuzzy set and cost performance index. The developed prototype is discussed along with detailed performance.

Scheduling Multiple Parameter Sweep Workflow Instances on the Grid

Due to its ability to provide high-performance computing environment, the grid has become an important infrastructure to support eScience. To utilise the grid for parameter sweep experiments, workflow technology combined with tools such as Nimrod/K are used to orchestrate and automate scientific services provided on the grid. As parameter sweeping over a workflow needs to be executed numerous times, it is more efficient to execute multiple instances of the workflow in parallel. However, this parallel execution can be delayed as every workflow instance requires the same set of resources leading to resource competition problem. Although many algorithms exist for scheduling grid workflows, there is little effort in considering multiple workflow instances and resource competition in the scheduling process. In this paper, we proposed a scheduling algorithm for parameter sweep workflow based on resource competition. The proposed algorithm aims to support multiple workflow instances and avoid allocating resources with high resource competition to minimise delay due to the blocking of tasks. The result is evaluated using simulation to compare with an existing scheduling algorithm.

Towards an adaptive mediation framework for Mobile Social Network in Proximity

Abstract Mobile Social Network in Proximity (MSNP) is a new form of social network in which users are capable of interacting with their surroundings via their mobile devices in public mobile peer-to-peer (MP2P) environments. MSNP brings opportunity to people to meet new friends, share device content, and perform various social activities. However, as the fundamental topology of MSNP is based on public MP2P network, many challenges have arisen. Existing related works restrict the MP2P social network to operate in specific platforms and protocols. Enabling MSNP in a dynamic public MP2P also requires a more flexible loosely-coupled service-oriented solution. Applying the service-oriented MSNP environment will enhance the interoperability of MSNP participants. However, the latency issue while performing dynamic service discovery and the resource constraint issue of devices, prevent the efficiency of MP2P-based service-oriented MSNP systems. In this paper, we propose an adaptive mobile-hosted service-oriented mediation framework for MSNP. The framework supports proactive service discovery by using context-aware user preference prediction scheme to reduce the latency caused by the service discovery process. In order to resolve the resource constraint issue, the mediation framework applied the Enterprise Service Bus architecture to support the runtime resource changes, and utilise resource-aware workflow mechanism to enable the dynamic adjustment of the execution behaviour at runtime based on the combination of fuzzy set and cost and performance index scheme.

Advanced Petri Nets for modelling mobile agent enabled interorganizational workflows

Mobile agents are a powerful abstraction for conceptualizing flexible large scale distributed workflows. Practically, we can use mobile agents to synchronize workflows of different organizations resulting in an interorganizational workflow. This paper discusses how mobile agent enabled interorganizational workflows can be usefully modelled using advanced Petri Net techniques such as Interorganizational Workflow Nets. This model provides a means to verify the correctness (and, so the viability) of the itineraries of agents used in enacting interorganizational workflows. We also outline an algorithm for our verification method. We also propose how Object Petri Nets can be used to properly model the agents own itinerary differently from the overall workflow potentially permitting agent reflection on its own itinerary in case of host failures or disconnections as in mobile computing environments. We believe that such modelling can provide a formal basis for analyzing mobile agent enabled interorganizational workflows that span stationary and mobile hosts.

ProMWS: Proactive mobile Web service provision using context-awareness

Applying Web service in mobile peer-to-peer service provisioning enhances the interoperability and resolves the heterogeneous challenges of ubiquitous environments. However, due to the nature of mobile peer-to-peer environments, a central repository for assisting service discovery is nonexistent, service discovery process relies on routing techniques, which increase the latency of the service interaction. This paper introduces ProMWS, a context-aware mobile Web service pre-fetching strategy to enable proactive service provisioning based on user preference and context. The proposed strategy predicts the mobile users query, and cooperates with remote services to pre-fetch the service to the cache of mobile device in advance before the user requests for it.

RFID-based user profiling of fashion preferences: blueprint for a smart wardrobe

In this paper, we explore the possibility of generating user profiles of fashion preferences from information captured by RFID technology. Proposing a design of a smart wardrobe, we investigate the appropriateness of the technology as an identification tool of real objects and to aid in detecting and tracking real objects movements. We then present a model of user fashion profile, which is generated through queries and data mining techniques. In order to illustrate the usefulness and real world feasibility of our proposed model, we build a working prototype as proof of concept. For evaluation purposes, we have created a random generator, which is able to generate random clothing items and dressing events that serve as input to our model for creating user profiles. Our experimental results clearly indicate that RFID technology is suitable to aid in creating smart systems.

Constructing interoperable components in distributed systems

The separation of architecture definition language (ADL) and interface definition language (IDL) is widely accepted in the distributed system community. It separates issues of hierarchical composition and configuration from those of services, communication and synchronisation and thus eases reconfiguration without changing the interfaces and implementation and allows the change of services within well-defined configuration constraints. Our approach towards distributed system definition draws on the Darwin projects notion of distributed system architecture definition and on Eiffels notion of design-by-contract. We extend contracts to deal with synchronisation and coordination at a higher level, explicitly targeting both large-scale loosely-coupled distributed components and tightly coupled parallel or multithreaded objects. In this paper we present a Java binding of the resulting contract extensions. We incorporate annotations into Java programs adding Eiffel-style assertions and other contractual constraints. Java component code and constraints are then associated to architectural diagrams in a visual programming environment. The paper illustrates the language features in a case study of a lift control system. Based on the case study, the component-based design approach is illustrated and the internal synchronisation of method execution is explained.