1. System Design
Ashima Wadhwa

2. What is system design?
High level design identifying the system processes, functional components and their interfaces
Derived from system requirements
Provides an overview of the project
Define the components that are needed
Establish how components “communicate” with other components
Determine how to modularize the project into discrete work packages
Identify critical interfaces that must be well defined
Used to provide initial cost, schedule & resource estimates
Usually little or few implementation details
As system design is refined, and lower level subsystems are included, implementation issues may need to be addressed

3. System design steps Define project goal and objectives
Develop the project system requirements
Identify the major system components that satisfy the system requirements
Identify the major system interfaces
Refine the system design
Define subsystems making up each component
Specify interfaces between subsystems
Establish management controls for the system interfaces

4. Coupling between modules in a software system must be minimized.
Modularity
Modularity means breaking a large project into smaller parts that can be understood and handled easily. In other words, modularity means dividing a large task into small tasks that can communicate with each other. The structure chart discussed in the previous section shows the modularity in the elevator system. There are two main concerns when a system is divided into modules: coupling and cohesion.
Coupling is a measure of how tightly two modules are bound to each other. i
Coupling between modules in a software system must be minimized.

5. Cohesion between modules in a software system must be maximized.
Another issue in modularity is cohesion. Cohesion is a measure of how closely the modules in a system are related. We need to have maximum possible cohesion between modules in a software system. i
Cohesion between modules in a software system must be maximized.

6. Software quality
The quality of software created at the implementation phase is a very important issue. A software system of high quality is one that satisfies the user’s requirements, meets the operating standards of the organization, and runs efficiently on the hardware for which it was developed. However, if we want to achieve a software system of high quality, we must be able to define some attributes of quality.

7. Software quality factors
Software quality can be divided into three broad measures: operability, maintainability and transferability. Each of these measures can be further broken down as shown in Figure

8. Data Validation
Data validation is the process of checking database to ensure that the information gathered from different data sources is clean, accurate and in a standard format. Data validation can be simple or complex, depending upon the way it is performed. For example, validating address, or phone numbers is easy. On the other hand, checking different data fields for consistency and accuracy in a master database will be complex.

9. Types of data validation techniques :
Form Level Validation: It ensures that all the fields marked as mandatory in the web form are filled correctly before the user clicks the submit button on the page
Field Level Validation: It makes certain that users enter correct value across a specific data field. For example, “Name” field can’t have a numeric value, and “ ” field should contain a value having “.” and
Data Saving Validation: Data saving validation is used for multiple data entry forms and option screens. User is allowed to save data on any or all tabs/pages before leaving the page.
Search Criteria Validation: This type of validation is used when there are multiple search criteria in a form, and user wants to save the search results before navigating to a different page
Range Validation: This validation type is used to make sure that the numeric value, characters or date entered is within the specific range

10. The Human machine Interface
The interface is the system which helps users communicate with the computer system and/or the application system

11. User Interface Design Objectives
To design a better user interface, use the following objectives:
Effectiveness as achieved through design of interfaces that allow the user to access the system in a way that is congruent with their individual needs
Efficiency as demonstrated through interfaces that increase speed of data entry, and reduce errors

12. User Interface Design Objectives
Further interface design objectives
User consideration as demonstrated in designing suitable interfaces, and providing appropriate feedback to users from the system
Generating usable queries
Productivity as shown through following sound principles of design for user interfaces and work spaces

13. Components of the HM Interface
The user interface has two main components
Presentation language, which is the computer-to-human part of the transaction
Action language that characterizes the human-to-computer portion

14. Types of Human Machine Interfaces
There are several types of interfaces:
Natural-language interfaces
Question-and-answer interfaces
A menu interface
Form-fill interfaces
Command-language interfaces
Graphical User Interfaces (GUIs)

15. Natural-Language Interfaces
Natural-language interfaces permit users to interact with the computer in their everyday or "natural" language

16. Question-and-Answer Interfaces
The computer displays a question for the user on the screen
The user enters an answer via the keyboard
The computer acts on that input information in a preprogrammed manner
New users may find the question-and-answer interface most comfortable

17. A Menu Interface
A menu interface, which provides the user with an onscreen list of available selections
A nested menu is a menu which can be reached through another menu

18. Advantages of Nested Menus
The advantages of nested menus are
Nested menus give a less cluttered screen
Nested menus eliminate menu options which do not interest a user
Nested menus allow users to move quickly through the program

19. Graphical User Interface (GUI) Menus
GUI menus guidelines
The main menu is always on the screen
The main menu uses single words
The main menu should have secondary menus grouped into similar features

20. Graphical User Interface (GUI) Menus
Further GUI menus guidelines
The secondary drop-down menus often consist of more than one word
Secondary options perform actions or display additional menu options
Menu items in gray are unavailable for the current activity

21. Form-Fill Interfaces
Form-fill interfaces are onscreen forms displaying fields containing data items or parameters that need to be communicated to the user
Form-fill interfaces may be implemented using the Web

22. Advantages and Disadvantages of Web Forms
Advantages of using a Web-based form
User enters the data
Data may be entered 24 hours a day, globally
Disadvantages of a Web-based form
The user may not know what to enter if the form is not clear
User might be nervous about using a credit card over the Internet

23. Command-Language Interfaces
Command-language interfaces are more popular than the previous ones
Allow the user to control the application with a series of keystrokes, commands, phrases, or some sequence of these

24. Graphical User Interfaces (GUIs)
GUIs provide a strong metaphor of the application
Allow direct manipulation of the graphical representation on the screen
Can be accomplished with keyboard input, joystick, or mouse
Requires more system sophistication than other interfaces

25. Dialog Dialog is the communication between a person and the computer
Three key points to be considered
Meaningful communication
Minimal user action
Standard operation and consistency

26. Thank You!!