Modelling and Simulation for e-Social Science Through the Use of Service-Orientation and Web 2.0 Technologies

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Townend, Paul Michael; Xu, Jie; Birkin, Mark; Turner, Andy; Wu, Belinda

MoSeS (Modelling and Simulation for e-Social Science) is a research node of the National Centre for e-Social Science, and is based at the University of Leeds. MoSeS aims to use e-Science techniques to develop a national demographic model and simulation of the UK population, specified at the level of individuals and households. Through MoSeS, users such a town planners can forecast trends in UK healthcare, business and transport, as well as demographic changes going forward dozens of years. Specifically, MoSeS aims to develop scenarios in the domains of health, transport, and business. For example, one health scenario would be to provide perspectives on medical and social care within local communities for a dynamic and ageing population. A scenario in the transport domain might concern the sustainability of transport networks in response to demographic change and economic restructuring, such as what kind of transport network is capable of sustaining long-term economic growth in West Yorkshire, Greater Manchester, and the intervening areas, etc.

Until recently, user interaction with MoSeS models has been achieved through a series of JSR-168 compliant portlets, which offers users a web-based interface to MoSeS. From this interface, facilities are available to analyse simulation results, to produce charts and tables of the results of these analyses (a user may, for example, wish to generate pie charts showing racial distribution in a specific area), and to generate and display simple shaded maps of results (for example, showing car ownership per ward in the Leeds area). These facilities are effective as an initial demonstrator, but in order to exploit the full potential of e-social science technologies, more flexible and advanced interfaces to MoSeS are necessary; this paper explores new capabilities offered by exposing MoSeS functionality through service-orientation and Web 2.0 technologies.

Service-orientation is emerging as a highly useful means of developing flexible, agile, and dependable software systems. A service can be defined as "_a mechanism to enable access to a set of one or more capabilities, where the access is provided using a prescribed interface and is exercised consistent with constraints and policies as specified by the service description._", whilst a service-oriented architecture can be defined as " an application architecture within which all functions are defined as independent services with well-defined invokable interfaces, which can be called in defined sequences to form business processes. " Service-orientation aims to facilitate the development of complex, dynamic, inter-organisational systems as well as to greatly simplify the process of integrating existing legacy systems, and has a profound impact on the software development process.

In recent months, the MoSeS project has been working to expose core MoSeS functionality as publicly accessible Web Services. This brings about many benefits; firstly, new analyses and visualizations can be created by both developers and users without any knowledge of programming; instead, new workflows (which can be defined as the description of the sequence of services that must be invoked to form a given scientific process) can be created through high-level workflow engines, such as Taverna and ActiveBPEL. Secondly, MoSeS processing can easily be distributed simply by invoking MoSeS services in parallel across different machines; additionally, a level of fault-tolerance can be introduced into processing by, for example, invoking multiple MoSeS services in parallel and either cross-checking their results or else using the results of the first service to fail without raising an exception. This can also lead to performance gains, as multiple services can be invoked and the first result to be returned used in the ongoing workflow. Thirdly, by exposing MoSeS functionality in a service-oriented way, it becomes possible to quickly create new interfaces to MoSeS - services can be accessed and used by programs written in any language, and GUI clients can be created as front ends to both workflows and individual services. Maintenance and new features added to any one service would then be reflected in all the applications that invoke that service. Similarly, current and future e-Social Science applications will also be able to easily exploit MoSeS functionality simply through invoking the MoSeS services via their standard interface.

In addition to service-orientation, MoSeS has been seeking to exploit a number of Web 2.0 technologies, particularly those related to mapping. Web 2.0 is defined by O'Reilly as " the business revolution in the computer industry caused by the move to the internet as platform, and an attempt to understand the rules for success on that new platform ". Although the mapping functionality previously used by MoSeS (shapefiles rendered as raster images through GeoTools libraries) provided a useful visualization of MoSeS analyses, the maps exposed little additional information that a user might require, and were limited in their interactivity. As a solution to this, MoSeS now has the capability to render map information using Web 2.0 technology in both dynamic OpenLayers maps (similar in functionality to Google Maps) and the Google Earth application. This is performed primarily through the use of GeoServer technology, with map styling being performed through a new MoSeS service which generates Styled Layer Descriptor (SLD) files to shade the map using colour values based on the data that the user wishes to visualise. Additional information, such as place names, roads, etc, can then be layered on top of this visualization.

This paper seeks to discuss both the benefits and disadvantages of the MoSeS project's move towards service-orientation, as well as how the service-oriented paradigm effects e-Social Science as a whole. Additionally, this paper describes the use of Web 2.0 technology within MoSeS in greater detail, and discusses the benefits and pitfalls of using this technology in e-Social Science.

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