CM322 Business Modelling for Internet Based Technology

1
CM322 Business Modelling for Internet Based
Technology

• Applied Business Modelling

2
Web Application Design

• Architecture
• Which objects go where?
• The final model
• notation
• Summary

3
Architecture

• Why should the architecture affect the app.?
• Recap
• single tier
• two tier
• three tier

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Partitioning the application

• Three fundamental parts
• Presentation
• means by which app. displays output and accepts
  input
• Logic
• computation that is programmed into the
  application
• Data
• quantities and values that your app. processes
  and stores

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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.)

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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

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Three tier

• Presentation layer resident on client
• Logic performed by separate server
• Data on network database server
• Quick to change logic without affecting users
• Clients OS must be compatible with Logic
  servers OS
• Still dependent on network performance
• Presentation at mercy of weakest computer - 16
  colour client cannot display photos

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Web App. Architecture

• With three tier, we can use a browser for
  presentation
• Only has to process ASCII text-based HTML to
  produce web pages
• Platform independent
• To be operational, two things are required
• Browser must be on desktop machine
• Desktop needs access to network via TCP/IP
• Thin Client

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Example
tutor
input attendance
input marks
ltltincludegtgt
ltltincludegtgt
authenticate
ltltincludegtgt
ltltincludegtgt
check marks
login
ltltincludegtgt
Why is this ltltincludegtgt? Should it not be
ltltextendgtgt?
student
get mark scheme
create marking scheme
read timetable
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Example - presentation
tutor
input attendance
input marks
ltltincludegtgt
authenticate
ltltincludegtgt
ltltincludegtgt
ltltincludegtgt
check marks
login
ltltincludegtgt
student
get mark scheme
create marking scheme
read timetable
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Example - logic
tutor
input attendance
input marks
ltltincludegtgt
authenticate
ltltincludegtgt
ltltincludegtgt
ltltincludegtgt
check marks
login
ltltincludegtgt
student
get mark scheme
create marking scheme
read timetable
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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
ltltincludegtgt
ltltincludegtgt
authenticate
ltltincludegtgt
ltltincludegtgt
check marks
login
ltltincludegtgt
..similarly if we are creating a new marking
scheme then it must be saved somewhere - in a
database object
student
get mark scheme
create marking scheme
read timetable
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So far...

• We have identified the users 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

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All we need to do now is

• Map the application logic to the users
  requirements
• Develop the navigation
• Decide what the user will see
• Communicate our design with the user and coder

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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
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Example
valid login
redirect
authenticate tutor login
click tutor index link
invalid user
invalid login
redirect
authenticate login
valid login
click timetable link
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Technology - CGI
valid login
redirect
chcltlog.cgi
click tutor index link
invalid user
invalid login
redirect
chcklog.cgi
valid login
click timetable link
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Technology - ASP
valid login
redirect
chcltlog.asp
click tutor index link
invalid user
invalid login
redirect
chcklog.asp
valid login
click timetable link
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Technology - JSP
valid login
redirect
chcltlog.jsp
click tutor index link
invalid user
invalid login
redirect
chcklog.jsp
valid login
click timetable link
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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

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Summary 2

• Proper partitioning of the business objects in a
  Web App. is critical and depends on the
  architecture
• In Thin Web Client apps., actors interact only
  with client pages
• Server pages interact only with server resources
• In Thick Web Client apps., client can execute
  business logic with scripts, applets or ActiveX
  (Microsoft) components

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Summary 3

• Various technologies to use
• Common Gateway Interface server-side scripts
• Java Server Pages
• VBscript on client
• JavaScript on client
• Active Server Pages