MWSMF: A Mediation Framework Realizing Scalable Mobile Web Service Provisioning Satish Narayana Srirama 1 , Matthias Jarke 1,2 1
RWTH Aachen, Informatik V Ahornstrasse 55, 52056 Aachen, Germany
Wolfgang Prinz 1,2 2 Fraunhofer FIT Schloss Birlinghoven 53754 Sankt Augustin, Germany
[email protected]
{srirama, jarke}@cs.rwth-aachen.de ABSTRACT It is now feasible to invoke basic web services on a smart phone due to the advances in wireless devices and mobile communication technologies. While mobile web service clients are common these days, we have studied the scope of providing web services from smart phones. Although the applications possible with Mobile Host are quite welcoming, the scalability of such a Mobile Host is observed to be considerably low. In the scalability analysis of our Mobile Host, we have observed that binary compression of SOAP messages being exchanged over cellular network have greatly improved the performance of the Mobile Host. While binary compression is observed to be very efficient, the mechanism has raised the need for an intermediary in the mobile web service invocation cycle. The paper addresses our mobile web service message optimization scenario, at the enterprise service bus technology based mediation framework, with evaluation results.
1. INTRODUCTION From the view-point of information systems engineering, the Internet has lead the evolution from static content to web services. Web services are software components that can be accessed over the Internet using well established web mechanisms, XML-based open standards and transport protocols such as SOAP and HTTP. Public interfaces of web services are defined and described using Web Service Description Language (WSDL), regardless of their platforms, implementation details. Web services have wide range of applications and primarily used for integration of different organizations. The biggest advantage of web services technology lies in its simplicity in expression, communication and servicing. The componentized architecture of web services also makes them reusable, thereby reducing the development time and costs. [10] Concurrently, the capabilities of high-end mobile phones and
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PDAs have increased significantly, both in terms of processing powers and memory capabilities. The smart phones are becoming pervasive and are being used in wide range of applications like location based services, mobile banking services, ubiquitous computing etc. The market capture of such smart phones is quite evident. The higher data transmission rates achieved in wireless domains with 3G and 4G technologies and the fast creeping of all-ip broadband based mobile networks also boosted this growth in the cellular market. The situation brings out a large scope and demand for software applications for such high-end smart phones. To meet this demand of the cellular domain and to reap the benefits of the fast growing web services domain and standards, the scope of the mobile terminals as both web services clients and providers is being observed. While mobile web service clients are common these days [7, 4], we have studied the scope of mobile web service provisioning in one of our previous projects. In this project, we have developed a Mobile Host [19], capable of providing basic web services from smart phones. Extensive performance analysis of the Mobile Host was conducted and many applications were designed and developed proving the feasibility of concept. While the applications possible with Mobile Host are quite welcoming, during the performance analysis of the Mobile Host, we have observed the scalability of the Mobile Host to be considerably low. We define scalability as the Mobile Host’s ability to process reasonable number of clients, over long durations, without failure and without seriously impeding normal functioning of the smart phone for the user. For improving the scalability of the Mobile Host the mobile web service messages exchanged over the radio link are to be compressed without seriously affecting their interoperability. Different compression techniques are studied in detail and BinXML [8] was identified to be the best possible compression option and the binary encoding was adapted for the mobile web service invocation cycle. While BinXML is observed to be very efficient for the mobile web service message compression, the encoding mechanism has raised the need for an intermediary or a middleware framework in the mobile web service invocation cycle. The mediation framework should encode/decode the mobile web service messages to/from XML/BinXML formats in the mobile operator proprietary networks. During our Mobile Host’s application, QoS and discovery research, we
have identified the final deployment scenario of Mobile Hosts in the cellular networks. The Mobile Web Services Mediation Framework (MWSMF) is established as an intermediary between the web service clients and the Mobile Hosts based on the Enterprise Service Bus (ESB) technology. The features, realization details and performance analysis of the mediation framework, specific to maintaining scalability of the Mobile Host are addressed in this paper. The rest of the paper is organized as follows: Section 2 discusses the concept of mobile web service provisioning. Section 3 addresses scalability analysis of the Mobile Host. Section 4 discusses the components and realization details of the mobile web services mediation framework, while section 5 provides the evaluation of the MWSMF. Section 6 summarizes the results and concludes the paper.
2. MOBILE WEB SERVICE PROVISIONING Service Oriented Architecture (SOA) [6] is a component model that delivers application functionality as services to end-user applications and other services, bringing the benefits of loose coupling and encapsulation to the enterprise application integration. SOA is not a new notion and many technologies like CORBA and DCOM at least partly represent this idea. Web services are newest of these developments and by far the best means of achieving SOA. Using web services for SOA provides certain advantages over other technologies. Specifically, web services are based on a set of still evolving, though well-defined W3C standards that allow much more than just defining interfaces. The quest for enabling these open XML web service interfaces and standardized protocols also on the radio link, with the latest developments in cellular domain, lead to a new domain of applications, mobile web services. The developments in cellular world are two folded; firstly there is a significant improvement in device capabilities like better memory and processing power and secondly with the latest developments in mobile communication technologies with 3G and 4G technologies, higher data transmission rates in the order of few mbs were achieved. In the mobile web services domain, the resource constrained mobile devices are used as both web service clients and providers, still preserving the basic web services architecture in the wireless environments. While mobile web service clients are quite common these days [7, 4], the research with providing web services from smart phones is still sparse. In our mobile web service provisioning project one such Mobile Host was developed proving the feasibility of concept [19]. Figure 1 shows the deployment scenario of mobile web services, where mobile devices are used as both web service providers and clients. Mobile Host is a light weight web service provider built for resource constrained devices like cellular phones. It has been developed as a web service handler built on top of a normal Web server. The SOAP based web service requests sent by HTTP tunneling are diverted and handled by the web service handler component. The Mobile Host was developed in PersonalJava on a SonyEricsson P800 smart phone. The footprint of the fully functional prototype is only 130 KB. Open source kSOAP2 [12] was used for creating and handling the SOAP messages.
Figure 1: Mobile terminals as web service providers and clients The detailed evaluation of this Mobile Host clearly showed that service delivery as well as service administration can be done with reasonable ergonomic quality by normal mobile phone users. As the most important result, it turns out that the total web service processing time at the Mobile Host is only a small fraction of the total request-response time (
