POLOS Platform Architecture

The PoLoS project aims to design specify and implement an Integrated Platform, which will cater for the full range of issues concerning the provision of Location Based Services (LBS). This platform will enable the specification, creation and deployment of such services within the premises of service operators, without any additional requirement in terms of network platforms or terminal devices. The Unified Modeling Language (UML) will be used for defining the PoLoS architectural and functional aspects. Languages like SDL may also be utilised if relevant need arises.

The PoLoS platform will provide the full functionality needed by both the Service Operator, which will deploy the location based service, as well as the end user, who will take advantage of the deployed service. To achieve this functionality, the PoLoS platform will feature a component-based architecture. Each component within this modular architecture will have a specific and clearly defined functionality. The two main entities defined within the PoLoS platform are the PoLoS Kernel and the Peripheral Components. The overall architecture of the pursued platform is shown in Figure 2 .

Figure 2: Target Architecture

Moreover, within the scope of the project is the development of a Service Creation Environment (SCE) for creating location-based services. More details on these environment is provided in following paragraphs.

PoLoS kernel

The PoLoS kernel comprises the primary component of the pursued platform. It will be developed using java-based technologies (e.g. JAVA, J2EE) and its functionality will be the co-ordination of the rest of the components in order to provide the functionality specified for each location-based service. Moreover, the PoLoS architecture will feature an interface, which will allow the PoLoS kernel to determine the capabilities of the mobile terminal. This interface will capitalise on the MExE technology.

Peripheral Components

 Three peripheral components are clearly identified within the PoLoS architecture:

 1.      The GIS component

2.      The Positioning component

3.      The Interfaces component

 Each of the above mentioned components is responsible for providing a certain function within the PoLoS platform. Communication between the components if required will be made through the kernel. Furthermore communication between the kernel and the peripheral components can be based either on XML formatted messages or implemented through well-defined APIs.

The GIS Component

The GIS Component is responsible for the interaction with deployed GIS repositories. It may include various software modules, as shown in Figure 2 to cover both visual as well as textual information. The purpose of these modules will be the exploitation of the wealth of information stored in GIS servers in order to create a graphical representation (e.g. map) of the area, where a specific service is going to be deployed.

The GIS Component will be invoked by the PoLoS kernel whenever necessary in order to provide the information needed for the provision of a certain service. This information can be used either internally (by the kernel or another component) or be transmitted to the mobile terminal (e.g., a graphics file) as part of the information provided by the specified service. A protocol between the GIS component and the GIS repository will be developed, possibly by exploiting the capabilities of XML. Such protocol will signal the information requirements of the Kernel to the remote end and retrieve information as needed. 

The Positioning Component

The Positioning Component will be responsible for providing the PoLoS kernel with the appropriate information pertaining to the position of a mobile terminal accessing a particular service. In order to acquire this information the component will use available positioning techniques provided by the underlying network. Determining the position of a mobile terminal can be based either on satellite-based systems (e.g. GPS), terrestrial infrastructure-based systems (e.g. TOA, E-OTD) or hybrid systems (e.g. D-GPS). Access to the network will be implemented through the OSA interface. Furthermore, special provision will be taken to (alternatively) interface the system to 3G network components like the Gateway Mobile Location Center (GMLC) as they become available in the operatorís infrastructure. 

The Interfaces Component

The Interfaces Component is responsible for communicating the service specific information to the mobile terminal. The interface will support different transport protocols from SMS and WAP to IP and the PoLoS kernel will invoke the appropriate, for each terminal, protocol in order to transmit service specific information to the terminal. Depending on the capabilities of the terminal and the requirements of the location based service to be accessed information exchanged could vary from simple textual data to downloading of small software modules in order to be executed in the environment of the mobile terminal (i.e. using MExE). Additionally, depending on the technology used by the terminal, protocols could be extended to accommodate geographical information (e.g., similarly to the longitude/latitude elements introduced in the so-called Dynamic URL scheme). 

Service Creation Environment 

Development of the Service Creation Environment (SCE) will focus on the design of an appropriate service specification language, a language capable to support the description of the functionality pertaining to each service. This language will be based on analogous languages that exist today hence it is highly probable that it will capitalize on the XML technology. The language will be flexible, and easy to use in order to allow for the specification and easy deployment of any type of LBS without too much effort and cost from the service provider. Each service will be defined through scripts written in this new language. Such scripts will run in the PoLoS kernel, which in turn will invoke the peripheral components, in order to provide the functionality needed for each service. To render the use of the language as efficient as possible, the project will also pursue the design of an integrated development environment (IDE) that will greatly facilitate the development and deployment of new services.