1. Logical and Physical Design of an Information System

2. Logical Design of an IS
You develop the logical design of an information system during the systems analysis phase.
The logical design defines the functions and features of the system and the relationship among its components.
The logical design includes the output that must be produced by the system, the input needed by the system, and the process that must be produced by the system without regard to how tasks will be accomplished physically.

3. Logical Design of an IS
a logical design defines what must take place, not how it is to be accomplished.
logical designs do not address the actual methods of implementation.

4. Example:
The Logical Design of a Customer Record System
describes the data that must be entered for each customer
specifies that records must be displayed in customer number order, and
explains what information to produce for a customer status report
Specifications for the actual input, or entry, of data, the sorting method, the physical process of creating the report, and the exact format of the report are not part of the logical design.

5. Physical Design of an IS
the physical design of an information system is a plan for the actual implementation of the system.
you develop the physical design during the systems design phase.
the physical design is built on the system’s logical design and describes a specific implementation, much like a working blue print describes the actual construction of a building.

6. Physical Design of an IS
the physical design describes the actual processes of entering, verifying, and storing data; the physical layout of data files; the sorting procedures; the exact format of reports; and so on.
Whereas logical design is concerned with what the system must accomplish, physical design is concerned with how the system will meet those requirements.

7. The relationship of Logical and Physical design
good system design is impossible without careful, accurate system analysis.
the design phase typically cannot begin until the analysis work is complete. It is better to complete the analysis phase before moving on to systems design.

8. SYSTEMS ANALYSIS GUIDELINES

9. Three (3) main activities of system analysis phase:
STEP
ACTIVITY
DESCRIPTION 1
Requirements modeling
Involves fact-finding to describe the current system and identification of the requirement s for the new system, such as outputs, inputs, processes, performance, and security. 2
Data and process modeling
A graphically modeling process to represent system data and process using traditional structured analysis techniques. Structured analysis identifies the data flowing into a process, the business rules that transform the data, and the resulting output data flow.

10. Development strategies
STEP
ACTIVITY
DESCRIPTION 3
Development strategies
In development strategies, you will consider various options and prepare for the transition to the systems design phase.
The deliverable, or end product, of the system analysis phase is a system requirement document, which is an overall design for the new system

11. SYSTEMS DESIGN GUIDELINES

12. Three (3) main activities of system design phase:
STEP
ACTIVITY
DESCRIPTION 1
Review system requirements
Become familiar with the logical design. 2
Design the system
User interface
Design an overall user interface, including screens, commands, controls, and features that enable users to interact with the application.
Input processes
Determine how data will be input to the system and design necessary source documents.

13. STEP
ACTIVITY
DESCRIPTION
Input and output
Design the physical layout for each input and output formats and reports screen and printed reports.
Data
Determine how data will be organized, stored, maintained, updated, accessed, and used.
System Architecture
Determine processing strategies and methods, client/server interaction, network configuration, and internet/intranet interface issues.

14. Present the system design
STEP
ACTIVITY
DESCRIPTION 3
Present the system design
Create the system design specification document, in which you describe the proposed system design, the anticipated benefits of the system, and the estimated development and implementation costs.

15. SYSTEM DESIGN CONSIDERATIONS User Consideration
Data Consideration
Architecture Consideration
Consider points where users interact with the system
Anticipate future user, system, and organizational needs
Enter data where and when it occurs
Verify data where it is input
Use automated data entry methods whenever possible
Control access for data entry
Report every instances of entry and change of data
Enter data only once
Use a modular design
Design independent modules that perform a single function

16. Logical System Design (System Analysis Phase)
Data Flow Diagrams
Data Dictionary
Process Descriptions
Physical System Design (System Design Phase)
Entity-Relationship Diagram
Normalization of Database
User Interface and Reports