Proposed Architecture and Implementation
To solve the limitations of the current architecture and implementation, we propose to move the geospatial rendering to the client-side with a more intuitive user interface that will be more responsive to user interaction and we will create an open and flexible server-side architecture that will allow for the addition of multiple data sources.
Architecture
In contrast to the current system, the service oriented architecture (SOA) allows for many services such as Google Maps, Web Feature Services (WFS), and ArcIMS to provide clients with data that is then rendered on the client-side using a Javascript-based tool called OpenLayers(see Figure 2).
OpenLayers is an open source Javascript library for delivering dynamic map content to any web page. It can display map tiles and markers loaded from any source and is supported by the open source community. By abstracting out the server side and setting up a common interface between the client and the server side, any map service or custom coded library can provided content and functionality to the client removing the limitation of waiting for the commercial vender to provide new features and bug fixes. User interaction will also be improved since the clients have more control over rendering and visualization; however, some of the advanced rendering capabilities provided by ArcIMS would have to be custom coded and there will be more computational load on the client. This increased computational load is partially mitigated by the increasing computational power available to common users.
!mm_arch_new.jpg!Figure 2. Proposed Architecture
Another advantage of this SOA is the ability to integrate current and future capabilities being developed by NCSA Cyberenvironments and Technologies (CET) division such as high performance computing access, scaling for large data, data analysis, provenance tracking, and metadata integration to deliver a richer user experience and to potentially collaborate on future projects to provide required functionality by the Market Maker Community.
Implementation and Technology
The development of the web mapping component will utilize an agile approach to software development and incorporate user feedback to deliver a high quality product. In the sections that follow, some high-level detail will be provided about the technologies that will be used and how they will be implemented in the component.
Server-Side
The initial server-side implementation of the component will consist of the OGC compliant Web Feature Server (WFS) and the Google Map API providing backend services to the client through an extensible service oriented architecture. These services will be made available to the client via a common API which will allow future technologies to be added as services and made available immediately to the client. The combination of WFS and Google Maps will illustrate the potential of this new architecture by seamlessly integrating data from the Web Feature Server, which will provide geospatial features like points, lines and polygons and services such as the Google Map API and ArcIMS Web Map Server which will provide map images.
The WFS will be implemented using Geoserver. The layers for the component, such as census tracts and business locations, will be defined as feature services under Geoserver.