Xitong Li

Multidimensional context-aware social network architecture for mobile crowdsensing

This article proposes a multidimensional context-aware social network architecture, which aims to provide a mobile ecosystem to enable context awareness in the development and utilization of mobile crowdsensing applications. This mobile ecosystem is constructed to provide context awareness capabilities for different roles (i.e., users or developers) in the system and facilitate interactions between them. This system can ease the development of context-aware mobile applications, and enable context-aware mobile crowdsensing considering environmental, personal, and social information. We present a flow of context-aware solutions designed on this system, and highlight the orchestrations and advantages of different context-aware schemes in the system for different types of users (requesters and participants) in mobile crowdsensing. We demonstrate the feasibility of the proposed mobile ecosystem by presenting a novel context-aware mobile crowdsensing application called Smart City, and evaluate the system performance based on this application.

A Petri Net Approach to Mediation-Aided Composition of Web Services

Recently, mediation-aided composition has been widely adopted when dealing with incompatibilities of services. However, existing approaches suffer from state space explosion in compatibility verification and cannot automatically generate the BPEL code. This paper presents a Petri net approach to mediation-aided composition of Web services. First, services are modeled as open WorkFlow Nets (oWFNs) and are composed using mediation transitions (MTs). Second, the modular reachability graph (MRG) of composition is automatically constructed and the compatibility is analyzed, so that the problem of state space explosion is significantly alleviated. Furthermore, an Event-Condition-Action (ECA) rule-based technique is developed to automatically generate the BPEL code of the composition, which can significantly save the time and labor of designers. Finally, the prototype system has been developed.

A pattern-based approach to protocol mediation for web services composition

Context: With the increasing popularity of Service Oriented Architecture (SOA), service composition is gaining momentum as the potential silver bullet for application integration. However, services are not always perfectly compatible and therefore cannot be directly composed. Service mediation, roughly classified into signature and protocol ones, thus becomes one key working area in SOA. Objective: As a challenging problem, protocol mediation is still open and existing approaches only provide partial solutions. Further investigation on a systematic approach is needed. Methods: In this paper, an approach based on mediator patterns is proposed to generate executable mediators and glue partially compatible services together. The mediation process and its main steps are introduced. By utilizing message mapping, a heuristic technique for identifying protocol mismatches and selecting appropriate mediator patterns is presented. The corresponding BPEL templates of these patterns are also developed. Results: A prototype system, namely Service Mediation Toolkit (SMT), has been implemented to validate the feasibility and effectiveness of the proposed approach. Conclusion: The approach along with the prototype system facilitate the existing practice of protocol mediation for Web services composition.

Dynamic Checking and Solution to Temporal Violations in Concurrent Workflow Processes

Current methods that deal with concurrent workflow temporal violations only focus on checking whether there are any temporal violations. They are not able to point out the path where the temporal violation happens and thus cannot provide specific solutions. This paper presents an approach based on a sprouting graph to find out the temporal violation paths in concurrent workflow processes as well as possible solutions to resolve the temporal violations. First, we model concurrent workflow processes with time workflow net and a sprouting graph. Second, we update the sprouting graph at the checking point. Finally, we find out the temporal violation paths and provide solutions. We apply the approach in a real business scenario to illustrate its advantages: 1) It can dynamically check temporal constraints of multiple concurrent workflow processes with resource constraints; 2) it can give the path information in the workflow processes where the temporal violation happens; and 3) it can provide solution to the temporal violation based on the analysis.

A Classification of Service Composition Mismatches to Support Service Mediation

On building a service-oriented architecture for grid systems, more and more researches have been focused on service composition. Services, however, are not always exactly compatible and much effort has to be addressed to mediate incompatible services, which is an unavoidable problem and recognized as service composition mismatches. To address it, a classification of composition mismatches is significant and helpful to divide the whole problem into different sub-problems which require corresponding mediators to deal with. However, there exist very few classification approaches specific to such problem and a comprehensive classification is still lacking. In this paper, a classification of most kinds of composition mismatches is introduced. Besides that, several basic protocol mismatch patterns are presented, which can be viewed as basic constructs of existing protocol mismatches. Finally, conclusions and the future work are drawn up.

A Pattern-Based Approach to Development of Service Mediators for Protocol Mediation

Service composition is one of the key objectives for adopting service oriented architecture. Today, Web services, however, are not always perfectly compatible and composition mismatches are common problems. Service mediation, generally classified into signature and protocol ones, thus becomes one key working area in SOA. While the former has received considerable attention, protocol mediation is still open and current approaches provide only partial solutions. In this paper, a pattern-based approach is proposed for developers to semi-automatically generate mediators and glue partially compatible services together. Based on the investigation on workflow patterns and message exchanging sequences in service interactions, several basic mediator patterns are developed and can be used to modularly construct advanced mediators that can resolve all possible protocol mismatches, especially such mismatches about complicated control logics. Moreover, the architecture for the service mediation system is designed and implemented to prove the feasibility of our approach.

An Approach to Composing Web Services with Context Heterogeneity

The potential benefits of Web services composition heavily rely on semantic interoperability, i.e., the ability to exchange data meaningfully amongst Web services. Context heterogeneity, which refers to different implicit assumptions about interpreting the exchanged data, hampers the automatic composition of Web services. However, existing initiatives of Semantic Web Services (SWSs) often ignore context heterogeneity. In this paper, we introduce an approach to address this issue. The contexts of the involved Web services are defined in a lightweight ontology and their WSDL descriptions are annotated by an extension of a W3C standard, i.e., Semantic Annotation for WSDL and XML Schema (SAWSDL). The composition of Web services is described using BPEL specification. Given a BPEL file that ignores context heterogeneity, the approach automatically detects all context differences among the involved services, and reconciles them by producing a mediated BPEL file that incorporates necessary conversions using XPath functions and/or Web services.

Measuring Effects of Observational Learning and Social-Network Word-of-Mouth (WOM) on the Sales of Daily-Deal Vouchers

In recent years, daily-deal sites that help sellers offer deep-discounted vouchers have become an increasingly popular marketing vehicle. To investigate their effectiveness on sales, this study hypothesizes two different mechanisms, i.e., observational learning and Word-of-Mouth (WOM) via online social networks, affect shopping behaviors and sales of daily-deal vouchers. Using a unique panel data set consisting of accurate sales data of more than 500 deals from Groupon.com, this study empirically tests saliency of the two mechanisms. The findings indicate that while both mechanisms have a significantly positive association with voucher sales, the effect is stronger for Facebook-mediated WOM than for observational learning. We find that one Facebook Like on a deal, on average, is associated with two additional voucher sales and thus an increase of

A Context-Based Approach to Reconciling Data Interpretation Conflicts in Web Services Composition

215 in revenue. However, we do not find consistent evidence that Twitter-mediated WOM has any impact on the voucher sales.

Herding and Social Media Word-of-Mouth: Evidence from Groupon

We present a comprehensive classification of data misinterpretation problems and develop an approach to automatic detection and reconciliation of data interpretation conflicts in Web services composition. The approach uses a lightweight ontology augmented with modifiers, contexts, and atomic conversions between the contexts. The WSDL descriptions of Web services are annotated to establish correspondences to the ontology. Given the naive Business Process Execution Language (BPEL) specification of the desired Web services composition with data interpretation conflicts, the approach can automatically detect the conflicts and produce the corresponding mediated BPEL. Finally, we develop a prototype to validate and evaluate the approach.