1. Chapter 13 Review Questions

2. 13.1
Give a definition of architecture in an information systems context.

3. 13.1 Answer System architecture shows the big picture.
High-level view of the system.
Architecture is the fundamental organization of a system which is modelled in terms of major components and the way they are connected to each other and to the environment.

4. 13.5
How do existing systems influence the architecture of new systems in the same organization?

5. 13.5 Answer
Firstly, the choice of existing technical aspects such as operating system, middleware, development language, database and the component or service structure of existing systems will influence those choices for the new system.

6. 13.5 Answer
Secondly, where there are reusable assets, such as components or services, the new system will be able to reuse these.
Thirdly, there may be existing systems whose architecture does not provide a pattern for future systems, and the architecture of the new system may have to interface to these through some kind of middleware or adapters.

7. 13.6
Explain the difference between a PIM(A platform-independent model) and PSM(platform-specific model ).

8. 13.6 Answer
A platform-independent model (PIM) is a model that does not contain any features that restrict it to implementation on a particular platform.

9. 13.6 Answer
A platform-specific model (PSM) is a transformation from a PIM to produce a model that can be implemented on a specific platform.

10. 13.8
What are the advantages of dividing a system into a collection of subsystems?

11. 13.8 Answer It has the following advantages:
It produces smaller units of development.
It helps to maximize reuse at the component level.
It helps the developers to cope with complexity.
It improves maintainability.
It aids portability.

12. 13.9
What is the difference between client-server and peer to peer communication?

13. 13.9 Answer Styles of communication between subsystems Client-server
Peer to peer

14. 13.9 Answer
Client–server communication requires the client to know the interface of the server subsystem, but the communication is only in one direction.
The client subsystem requests services from the server subsystem and not vice versa.

15. 13.9 Answer
Peer-to-peer communication requires each subsystem to know the interface of the other, thus coupling them more tightly. The communication is two way since either peer subsystem may request services from the other.

16. 13.10
Why is an open layered architecture more difficult to maintain?

17. 13.10 Answer
Open layered architectures are more difficult to maintain because each layer may communicate with all lower layers hence increasing the degree of coupling in the architecture. A change to one layer may ripple too many layers.

18. 13.11
What are the disadvantages of the closed layered architecture?

19. 13.11 Answer
A closed layer architecture many require more processing, as messages have to be passed through intervening layers.

20. 13.15
How do architectural divisions of systems help with project management?

21. 13.15 Answer
By breaking a system into subsystems, work can be allocated to teams more easily, with each team responsible for a particular subsystem.

22. Deciding Application Architecture
Data Processing System
Transaction Processing System
Event Processing System
Language Processing System

23. Deciding Application Architecture
Data Processing System
Data-driven
is explicit user interventions during the processing.
Large amount of data
input and outputs are processed from a file or database rather than input from and output to user terminal.
Low functionality(similar operations are carried out on a large amount of data.)
Example applications : market applications,telephone billing system

24. Deciding Application Architecture
Transaction Processing System
Applications that requires the inputs from a user and give outputs back to the user.
Most common type of interactive business systems.
User actions can’t interfere with each other.
The integrity of the database is maintained.
Example applications :interactive banking systems,e-commerce systems,booking systems.

25. Deciding Application Architecture
Event Processing System
Real-time systems
Events can occur unpredictably
Example applications : Games, car parking systems

26. Deciding Application Architecture
Language Processing System
compiler

27. System Architecture Client\Server Layered
Data Centered(Repository architecture)

28. Client\Server Consider this style if;
The application is Server based and supports multiple clients.
You are creating Web based applications exposed through browser.
You want to centralize data storage, backup and management functions.

29. Layered Used when building new facilities on top of existing systems;
There is a requirment for multi-level security.
Development is spread across several teams.

30. Layered 3 main layers the Data Access layer the Business Logic layer
the Graphical User Interface layer

31. Layered Consider the layered architecture style if;
Your application is complex
You want to improve the maintainability and extensibility of the application
clear separation of responsabilities 

32. Layered User Interface Authentication and Authorization
Core Business(system utilities)
Database

33. Data Centered(Repository architecture)
All data is accessible to all system components. Components do not interact directly, only through the repository.

34. Data Centered(Repository architecture)
Components are independent. They dont need to know each other.
All data can be managed consistently.