A01 chaf6542 06 se fm indd

 three-  tier   client–  server

 model where the cli-

ent is mainly used for display with application logic and the business rules partitioned on a 

server, which is the second tier, and the database server is the third tier. Since most of the 

processing is executed on the servers rather than the client, this architecture is sometimes 

referred to as a ‘

thin client

’, because the size of the executable program is smaller. The appli-

cation server provider (ASP) described in Chapter 3 is typically based upon the  three-  tier 

model. This is shown in Figure 11.7.

Although the  three-  tier model of a digital business system suggests a relatively simple 

architectural design, the reality is more complex. Different servers are needed which combine 

applications logic and database storage for different requirements. These may be physically 

separate servers or may be combined. Figure 11.8 shows a typical digital business architec-

ture. The purpose of each of the servers is as follows:

● 

Web server. Manages http requests from client and acts as a passive broker to other serv-

ers. Returns or serves web pages.

● 

Merchant server. This is the main location of the application logic and integrates the entire 

application by making requests to the other server components.

● 

Personalisation server. Provides tailored content – may be part of commerce server 

functionality.

● 

Payment commerce server. Manages payment systems and secure transactions.

● 

Catalogue server. A document management server used to display detailed product infor-

mation and technical specifications.

● 

CRM server. Stores information on all customer contacts.

● 

ERP server. Required for information on stock availability and pricing from the cus-

tomer. Will need to be accessed for sales order processing and histories, and logistics for 

distribution.

It is evident that designing the method of integration between different components is not 

straightforward – creating a fully integrated digital business is not straightforward! As was 

discussed in Chapter 9, the best approach to simplifying the design is to reduce the number 

of suppliers of components to improve the ease of data and applications integration.