Transcript Document

CM322 Business
Modelling for Internet
Based Technology
Applied Business Modelling
Web Application Design
Architecture
Which objects go where?
The final model

notation
Summary
Architecture
Why should the architecture affect the
app.?
Recap:
single tier
 two tier
 three tier

Partitioning the
application
Three fundamental parts

Presentation


Logic


means by which app. displays output and accepts input
computation that is programmed into the application
Data

quantities and values that your app. processes and
stores
Single tier
Presentation, Logic and Data all performed
on one machine
Known as ‘standalone’ application
Everything self-contained - no connection to
network required
Difficult to synchronise data with other
machines
Data integrity damaged by time delays - not
real-time changes
Change the logic, every machine to update
Platform dependent (PC, Mac, Unix etc.)
Two tier
Client-server framework
Data resides on server, Presentation and
Logic on client
Data is centralised
System performance subject to network
conditions and utilisation of server
Logic updates still apply to each client
Three tier
Presentation layer resident on client
Logic performed by separate server
Data on network database server
Quick to change logic without affecting users
Client’s OS must be compatible with Logic
server’s OS
Still dependent on network performance
Presentation at mercy of weakest computer 16 colour client cannot display photos
Web App. Architecture
With three tier, we can use a browser for
presentation


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Only has to process ASCII text-based HTML to
produce web pages
Platform independent
To be operational, two things are required:


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Browser must be on desktop machine
Desktop needs access to network via TCP/IP
Thin Client
Example
tutor
input attendance
input marks
<<include>>
<<include>>
<<include>>
authenticate
<<include>>
check marks
login
<<include>>
student
Why is this
<<include>>?
get mark scheme
create marking scheme
read timetable
Should it not be
<<extend>>?
Example - presentation
tutor
input attendance
input marks
<<include>>
<<include>>
<<include>>
<<include>>
check marks
login
<<include>>
student
get mark scheme
create marking scheme
read timetable
authenticate
Example - logic
tutor
input attendance
input marks
<<include>>
<<include>>
<<include>>
<<include>>
check marks
login
<<include>>
student
get mark scheme
create marking scheme
read timetable
authenticate
Example - data?
..and attendance marks must be
stored centrally (more data)...
tutor
input attendance
The use case text
gives us the complete
process - if we are
inputting marks then
we will have identified
a database object
input marks
<<include>>
<<include>>
<<include>>
authenticate
<<include>>
check marks
login
<<include>>
student
get mark scheme
create marking scheme
read timetable
..similarly if we are
creating a new marking
scheme then it must be
saved somewhere - in a
database object
So far...
We have identified the user’s requirements
and produced textual descriptions for each
operation
We have produced a use case diagram to
graphically represent the model
We identified the objects from the noun
phrases that had behaviour
We have examined the sequence of
messages passed between objects
All we need to do now is:
Map the application logic to the user’s
requirements
Develop the navigation
Decide what the user will see
Communicate our design with the user and
coder
Component Diagram
Notation
Document
that sends
output to
client otherwise
known as
‘client page’
navigation
link
Document that
does not send
output to client
- also referred
to as ‘server
page’
Example
redirect
login
invalid
login
authenticate
tutor login
click
tutor
index
link
invalid
user
bad login
tutor index
redirect
authenticate
login
valid
login
not tutor
valid
login
browse index
click
timetable
link
timetable
Technology - CGI
redirect
login.htm
invalid
login
chcltlog.cgi
click
tutor
index
link
invalid
user
badlogin.cgi
tutind.htm
redirect
chcklog.cgi
valid
login
nottut.cgi
valid
login
index.htm
click
timetable
link
tmetble.htm
Technology - ASP
redirect
login.asp
invalid
login
chcltlog.asp
click
tutor
index
link
invalid
user
badlogin.asp
tutind.asp
redirect
chcklog.asp
valid
login
nottut.asp
valid
login
index.asp
click
timetable
link
tmetble.asp
Technology - JSP
redirect
login.jsp
invalid
login
chcltlog.jsp
click
tutor
index
link
invalid
user
badlogin.jsp
tutind.jsp
redirect
chcklog.jsp
valid
login
nottut.jsp
valid
login
index.jsp
click
timetable
link
tmetble.jsp
Summary
Design is where the abstraction of the
business takes its first step into the
reality of software
Design starts with the analysis model
and architecture as the major inputs
The design model can be mapped
straight to code
Component diagrams visualise
components, interfaces and
relationships
Summary 2
Proper partitioning of the business
objects in a Web App. is critical and
depends on the architecture
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In Thin Web Client apps., actors interact
only with client pages;
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Server pages interact only with server
resources
In Thick Web Client apps., client can
execute business logic with scripts, applets
or ActiveX (Microsoft) components
Summary 3
Various technologies to use:
Common Gateway Interface server-side
scripts
 Java Server Pages
 VBscript on client
 JavaScript on client
 Active Server Pages
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