ISPRS Workshop on Service and Application of Spatial Data Infrastructure, XXXVI(4/W6), Oct.14-16, Hangzhou, China 
converting “take the product as its centre” into “take the service 
as its centre”. And the application server technology will further 
the converting process. 
without any consideration of the complex technique details on 
system layer. Additionally, business logic, which provides 
different functions for users, exits in a form of component on 
application server. Thus, it can be reused easily. 
3. MULTI-LAYER DISTRIBUTED ARCHITECTURE 
OF APPLICATION SERVER 
In the middle of 1980s, the C/S distributed computing 
technology appeared and was widely used on Internet since its 
convenience of using. However, it still has some shortage as 
follows: 
1. System with high complexity. Currently, the logic of 
geographical information system and its representation mixes 
together, which makes the system difficult to develop for 
program developers. And also leads to a system with low 
stability. 
2. System with less flexibility. Information technology, 
which is the technology base of geographical information 
service, develops rapidly. With new information technology 
appearing increasingly, geographical information technology, in 
order to provide better quality service to the public, should be 
updated accordingly. This means that the old and outdated 
technology should be taken by advanced ones. All these facts 
request the geographical information system should be renewed 
in time. 
3. System with low expansibility. Sometimes, users need 
more sendees but current geographical information system can 
not provide. In order to meet these new requests, geographical 
information system must be easily expanded. However, at 
present, the only way to meet these requests is to re-build the 
whole system, which is a difficult and time-consuming task for 
program developers. In this way, when the geographical 
information service system is expanded, the new system and the 
old can not be integrated. With the development of computer 
technology, B/S architecture that composed three layers— 
representation layer, business logic layer and data layer — 
gradually replaced the C/S architecture. It separate 
representation layer from business logic layer. Inasmuch as its 
abilities of platform crossing, balance loading and its portability, 
B/S architecture is very suitable to be employed in distributed 
computation environment. And application server, in this 
architecture, is an idea tool to implement the business logic 
layer that takes charge the process of business logic. 
Application server, which is considered to be one of the most 
exciting milestones of software technology since the relational 
database and has become very popular in the last few years, 
solves the problems in applying application to web computing 
environment and provides a platform that support the 
development, management, deployment, integration, and 
execution of web applications. The position of application 
server on Internet is showed in figure 1. 
Representation layer 
Business logic 
Data layer 
Figure 1. The position of application server on Internet 
4. MODEL OF GEOGRAPHIC INFORMATION 
SERVICE BASED ON APPLICATION SERVER 
GIS Application server, which is framed by broken line in 
figure 2, is the kernel of this model. It specializes in GIS 
function processing that has been separated from representation 
and data layer, and provides session connection, load balancing 
and access controlling for GIS components. 
Figure 2. The model of geographic information service based 
on application server 
This model is characterized by its high expandability. When a 
new geographic information service is needed, developers 
simply need to deploy a new GIS component, which either is 
designed by developers themselves or is buy from other 
company or is inherited from previous GIS component, into 
GIS application server. 
As it adopts component technology and modularized 
development method, application server facilitate developers 
adjust system functions by expanding or cutting down 
components according to the needs of users. This makes the 
system easy to be developed and maintained, and also enhances 
the system stability. Application server, by partitioning user 
interface, business logic and back-end service off from single 
complex logic, provides a modularized method for developers 
to construct, deploy and maintain enterprise web application. 
And it is also provides a high performance for web user 
accessing. With a simple structure and an efficient programming 
interface that application server provided, developers can 
concentrate their minds on the business logic layer designing, 
Request broker is in charge in request sending and response 
receiving. It is an agent to realize the communication between 
user and GIS application server. When a user proposes a service 
request, request broker sends the request and its parameters to 
GIS application server, and receive response returned from GIS 
application server, and forwards the response to user. This 
procedure is processed in the background. For users, it is not 
necessary to know where and how the GIS components execute 
their requests. 
GIS component, which is the key element of GIS application 
server, realizes geographic information service. It encapsulates