Geology Reference
In-Depth Information
server-based network. A client is defined as the
requestor of a service in a network where a server
then provides the service. The advantage is that a
distributed architecture permits dynamic combi-
nations and linkages between data services and
application services via networking. Consequently,
data can be stored on a suite of heterogeneous
servers and dynamically accessed at an applica-
tion's request. Potentially, distributed systems
will promote the development of accessible insti-
tutional data nodes that provide information to
Internet-based applications.
The Internet-GIS architecture determines the
complexity and efficiency provided by the appli-
cation. Currently, there are two types of Internet-
GIS applications: client (user)-side and server-side.
Client-side strategies require the majority of the
processing to be conducted by the client on their
own computer platforms. This typically requires
the web browser to load a program (such as an
applet or plug-in) the first time that users request
a service. This 'thicker client' architecture pro-
vides the advantage of more functionality for
users and requires fewer interactions with the
server, potentially saving time and using less
bandwidth. With this approach there are usually
fewer security risks. However, applets are not
persistent and must be downloaded at the incep-
tion of the application, and plug-ins are required
to be downloaded and installed like traditional
applications. This type of architecture is typically
best for applications with dedicated application
users (Plew, 1997) because users are required to
have knowledge of handling and manipulating
data. Server-side strategies perform all processing
on the server, relying on the spatial server to con-
duct the analysis and generate output (Peng,
1997). These 'thin-client' applications require a
high-performance server due to the computation
intensity, and have higher network congestion
since each operation performed by users must
communicate to the server, increasing the need
for bandwidth. However, users have transparent
access to large and complex datasets, so they do
not need either the software or the skills to
manipulate data. Users are not required to have
sophisticated computers since client machines
perform little processing (Foote & Kirvan, 1997).
Since tradeoffs exist between functionality, effi-
ciency and required knowledge, integrated deci-
sion support systems should support multiple
weight clients, providing access to users with dif-
ferent backgrounds, experiences, and network
connection speeds.
Most Internet-based applications that support
erosion modelling and control are thin-clients,
being distributed from a client/server system
(2- or 3-tier server architecture). For most erosion
model applications the user is requested to enter
the input information, so the data service require-
ments are relatively small.
17.3
Advantages of Internet-based
Applications
The goal of an Internet-based application is to pro-
vide information and tools to a user group in a
cost-effective manner. Internet-based applications
primarily save time and money by centralizing
activities. Databases and models can be main-
tained and located in the same place, with a single
update distributed to all potential client users.
A few database specialists can also maintain the
system for all client users. Advanced software,
such as GISs or statistical programs, can also be
centrally located on host computers. Consequently,
client users do not need to purchase or maintain
the software, assuming the licensing of proprie-
tary software for Internet use is available. Client
users can also rely on less powerful hardware sys-
tems in terms of processing and storage, since
most activities are accomplished on the host com-
puter. The system can also be made more secure.
The ultimate advantage of Internet-based
applications is that they promote data sharing
and equity between stakeholder groups. Internet-
based data services have become the primary
mechanism for the distribution of data and infor-
mation. Internet-based decision support tools,
such as erosion modelling applications, can pro-
vide advanced analysis capabilities to a wide and
untraditional audience. The increase in access to
information and analysis tools for all citizens
Search WWH ::




Custom Search