The Web GIS platform Server architecture is consisted of
three layers: User Interface Layer, Application Server Layer
and Database Layer. The figure 3 shows the Service oriented
architecture of GIS-T platform.
Application Server Layer. In the application server layer, the
GIS web services, Servlet/JSP interface, GCO services that
include GML and WMS map service, and basic system
application service deployed in the J2EE server container. The
GIS function such as the zooming out and in, viewing, panning
and finding be designed as a function session bean that can be
accessed by the GIS web service, Servlet/JSP and other
Application interfaces. The application server layer is built as a
J2EE application, with several EJB modules, to provide servercentric
spatial functions to applications. Key components of
the server that implemented as EJBs are Web GIS services,
Geo-spatial functions, such as the viewing, layer selection,
editing, querying, and analysis Data Source Management.
Database Layer. The GIS data are stored and managed with
the distributed systems architecture that enables the GIS data,
databases and services in the same or different computers. The
OpenGIS Consortium has provided specifications on spatial
entities and the space / time reference systems.
User Interface. Web GIS platform provides a number of
user interface components: Web service client, GIS java
Applet and any other web service enabled applications. The
mobile and PDA that support the web service standards
interface could get the map and geo-referenced data through
the GIS web service interface. A GIS Java Applet is another
user interface that can be used to retrieve and handle the vector
and raster map using the map tools. Java applet enables spatial
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viewing, querying, and richer editing capabilities to be easily
embedded in desktop and web applications.