sad(session-1)
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AMITY We nurture talent
Transcript of sad(session-1)
AMITY
We nurture talent
System Analysis and Design ADL-74
Session -1
OP SangwanAssistant Prof. & Head
CISCO Regional Networking Academy
Amity Institute of Information TechnologyAmity University---Uttar Pradesh---
Module 1 Concept of Information System
System Concept
• System is way of thinking about organizations and their problems.
• It involves a set of techniques that helps in solving problems.
• The term system is derived from the Greek word systema, which means an organized relationship among functioning units or components.
• The term system is also defined as an orderly grouping of interdependent components linked together according to a plan to achieve a specific objective.
Basics Implications with System
1. A system must be designed to achieve a predetermined objectives.
2. Interrelationalship and interdependence must exist among the components.
3. The objectives of the organization as a whole have a higher priority than objectives of its subsystems. For example, computerizing personnel applications must conform to the organization’s policy on privacy, confidentiality, and security, as well as making selected data (e.g. pay-roll) available to the accounting division on request.
Characteristics of a System• Organization
It implies structure and order. It is the arrangement of components that helps to achieve objectives. In the design of business system, for example, the hierarchical relationship starting with the president on top and leading downward to the blue-collar workers represents the organization structure.
• InteractionIt refers to the manner in which each component functions with other components of the system. In an organization, for example, purchasing must interact with production, advertising with sales, and payroll with personnel.
• InterdependenceInterdependence means that parts of the organization or computer system depend on one another.
Characteristics of a System
• IntegrationIntegration refers to the holism of systems. Integration is concerned with how a system is tied together.
• Central ObjectivesObjectives may be real or stated. The organization should have only one objective i.e. central objective. The important is that user must know the central objective of a system early in the analysis for a successful design and conversion.
Elements of a System
• Inputs and Outputs• Processor(s)
It is the operational components of system that performs the actual transformation from input to output.
• ControlIt is the decision-making (guides the system) subsystem that controls the pattern of activities governing input, processing, and output.
• FeedbackIt measures output against a standard in some form of cybernetic procedure that includes communication and control. Feedback may be positive or negative, routine or informal.
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Elements of a System
• EnvironmentThe environment is the “suprasystem” within which an organization operates. In fact, it often determines how a system must function.
• Boundaries and InterfaceA system should be defined by its boundaries-the limit that identify its components, processes, and interrelationships when it interfaces with another system. For example, a teller system in a commercial bank is restricted to the deposits, withdrawals, and related activities of customers and checking and saving accounts.
Types of System
• Physical or AbstractPhysical systems are tangible quantities that may be static (e.g. computer Centre) or dynamic (e.g. computer programme) in operation. Abstract systems are conceptual or nonphysical entities.
• Open or Closed An open system (e.g. information system) has many interfaces with its environment. It permits interaction across its boundaries.
A closed system is isolated from environmental influences.
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Types of System
• Man–Made information systemAn information system may be defined as a set of devices, procedures, and operating systems designed around user-based criteria to produce information and communicate it to the user for planning, control, and performance.
A formal Information System is based on the organization represented by the organization chart.
Categories of Information System
DSS (Decision Support System)-Designed to help decision makers-Provides interactive environment for decision making
MIS (Management Information System)-Converts raw data from transaction processing system into meaningful form
TPS (Transaction (Data) Processing System) -Automate handling of data about business activities (transactions)
Expert Systems (ES) -Replicates decision making process-Knowledge representation describes the way an expert would approach the
problem
Module 2Overview of Design of Information Systems
Software Development Life Cycle (SDLC)
• System Development Methodology– Standard process followed in an organization
– Consists of:• Analysis• Design• Implementation• Maintenance
SDLC
• Series of steps used to manage the phases of development for an information system
• Consists of six phases:– Project Identification and Selection
– Project Initiation and Planning
– Analysis
– Design
– Implementation
– Post implementation and Maintenance
SDLC
– Phases are not necessarily sequential
– Each phase has a specific outcome and deliverable
– Individual companies use customized life cycles
Phases of SDLC
• Project Identification and Selection– Two Main Activities
• Identification of need• Prioritization and translation of need into a development schedule
– Helps organization to determine whether or not resources should be dedicated to a project.
• Project Initiation and Planning– Two Activities
• Formal preliminary investigation of the problem at hand• Presentation of reasons why system should or should not be developed
by the organization
SDLC
• Analysis– Study of current procedures and information systems
• Recognition of needs– Study current system
– Structure requirements and eliminate redundancies
• Generate alternative designs
• Feasibility study
• Compare alternatives
• Recommend best alternative
The term design is used in two ways. Used as verb, it represents the process of design. Used as a noun, it represent the results of the system.
Design of system is essentially a blue print or plan for a solution for the system.
Design
TYPES OF DESIGN
• System Design or Top-Level Design
• Detailed Design or Logic Design
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Bottom-Up Design
Fig. : Bottom-up tree structure
These modules are collected together in the form of a “library”.
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DESIGN STRATEGYA good system design strategy is to organize the program modules in such a way that are easy to develop and latter to, change. Structured design techniques help developers to deal with the size and complexity of programs. Analysts create instructions for the developers about how code should be written and how pieces of code should fit together to form a program. It is important for two reasons:
First, even pre-existing code, if any, needs to be understood, organized and pieced together.
Second, it is still common for the project team to have to write some code and produce original programs that support the application logic of the system.
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Top-Down Design
A top down design approach starts by identifying the major modules of the system, decomposing them into their lower level modules and iterating until the desired level of detail is achieved. This is stepwise refinement; starting from an abstract design, in each step the design is refined to a more concrete level, until we reach a level where no more refinement is needed and the design can be implemented directly.
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Fig. : Top-down structure
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Hybrid Design
For top-down approach to be effective, some bottom-up approach is essential for the following reasons:
To permit common sub modules.
Near the bottom of the hierarchy, where the intuition is simpler, and the need for bottom-up testing is greater, because there are more number of modules at low levels than high levels.
In the use of pre-written library modules, in particular, reuse of modules.
Implementation
•Hardware and software installation•Programming•User Training•Documentation
SDLC
• Post Implementation and Maintenance
• Evaluation
• Maintenance
• Enhancements
• System changed to reflect changing conditions
• System obsolescence
System Analyst
• Systems analysts act as– Outside consultants to businesses
– Supporting experts within a business
– As change agents
• Analysts are problem solvers, and require communication skills
• Analysts must be ethical with users and customers
System Analyst Characteristics • Interpersonal Skills
Communication Understanding Teaching Selling ideas
• Technical Skills Creativity Problem Solving Project Management Dynamic Interfaces Questioning attitude and inquiring mind Knowledge of the basics of the computer and the business function
Role of System Analyst
• Change Agent• Investigator and Monitor• Architect• Psychologist• Salesperson• Motivator• Politician
Information Gathering(Categories of Information)
About the Organization• Policies• Goals• Objectives• Organization Structure
User Staff• Authority relationships• Job Function• Information Requirements• Interpersonal relationships
Information Gathering(Categories of Information)
Work Policies• Work Flow• Methods and Procedures• Work Schedules
Information GatheringTools
Review of Literature, Procedures, and Forms On-site Observation Interviews Questionnaires Joint Application Development (JAD)
• A structured group process focused on determining requirements
• Involves project team, users, and management working together
• May reduce scope creep by 50%
• Very useful technique
Structured Analysis
Structured analysis is a techniques to help defineWhat the system needs to do (processing requirements)
What data the system needs to store and use (data requirements)
What inputs and outputs are needed
How the functions work together to accomplish tasks
Tools of Structured Analysis
Module: 3
Tools of Structured Analysis Data Flow Diagram (DFD) Entity Relationship Diagram Data Dictionary Structured English Decision Trees Decision Tables Charts Structured Walk-Through Audit and Processing Control Documentation Plan
Data Flow Diagram (DFD)
Shows inputs, processes, storage and outputs and how they function together
Based on activities (processes) and data that flow in and out of them
Data Flow Diagram (DFD)
FIG : A data flow diagram (DFD) created using the structured technique
Entity Relationship Diagram
Focuses on identifying types of “things” (entities) which the system needs to store information about (e.g. customers, items and details)
Specifies relationships between these things or entities Used a lot for design of databases – you “carve up” your business
application into entities you will store data about
FIG: An entity-relationships diagram (ERD) created using the structured technique.
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Entity-Relationship Diagrams
It is a detailed logical representation of data for an organization and uses three main constructs.
Entities Relationships Attributes
Entities
Fundamental thing about which data may be maintained. Each entity has its own identity.
Entity Type is the description of all entities to which a common definition and common relationships and attributes apply.
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Entity-Relationship Diagrams
Consider an insurance company that offers both home and automobile insurance policies .These policies are offered to
individuals and businesses.
POLICY CUSTOMER
home Automobile individual businesses
POLICYCUSTOMER
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Relationships A relationship is a reason for associating two entity types.
Binary relationships involve two entity types
A CUSTOMER is insured by a POLICY. A POLICY CLAIM is made against a POLICY.
Relationships are represented by diamond notation in a ER diagram.
CUSTOMERInsured
byPOLICY
POLICYCLAIM
MadeAgainst
Relationships added to ERD
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A training department is interested in tracking which training courses each of its employee has completed.
Each employee may complete more than one course,and each course may be completed by more than one employee.
EMPLOYEE completes COURSE
Many-to Many relationship
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Degree of relationshipIt is the number of entity types that participates in that relationship.
Unary Binary Ternary
Unary relationship
PersonIs
Marriedto
EmployeeManagesOne to One
One to many
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Binary Relationship
EMPLOYEE PARKINGPLACE
Isassigned
PRODUCTLINE PRODUCTContains
STUDENT COURSERegistersfor
One to One
One to many
Many to many
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Ternary relationshipPart
Vendor Ware HouseShips
Cardinalities and optionality
Two entity types A,B, connected by a relationship.The cardinality of a relationship is the number of instances of entity B that can
be associated with each instance of entity A
Movie Video Tape
IsStocked
as
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Attributes
Each entity type has a set of attributes associated with it.
An attribute is a property or characteristic of an entity that is of interest to organization.
Attribute
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If there are more candidate keys, one of the key may be chosen as the Identifier.
It is used as unique characteristic for an entity type.
Identifier
A candidate key is an attribute or combination of attributes that uniquely identifies each instance of an entity type.
Student_IDCandidate Key
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STUDENTStudent_ID
Name Address
Phone_No
Vendors quote prices for several parts along with quantity of parts.Draw an E-R diagram.
Quote-price
Vendor Parts
pricequantity
Data DictionaryDefines data elements to avoid different interpretations. Example:
– Alien: “What’s a name?”
– Person: “Well, you know, it’s just a name. It’s what we call each other.”
– Alien: “Does that mean you can call them something different when you are angry or happy?”
– Person: “No, of course not. A name is the same all the time.”
– Alien: “Now I understand. My name is 3.141592653”.
– Person: “Oh your name is PI…But that’s a number, not a name. But what about your first and last name. Or is your first name 3, and your last name 141592653?”
Structured English
• Structured English is based on structured logic
• Simple English statements such as add, multiply, move, and so on
• It is an appropriate technique for analyzing the system when structured decisions are not complex
Decision Tree
• Decision trees are used when complex branching occurs in a structured decision process
• Trees are also useful when it is essential to keep a string of decisions in a particular sequence
Drawing Decision Tree
• First, identify all conditions and actions and the order and timing of these (if they are critical)
• Second, begin building the tree from left to right while making sure you are complete in listing all possible alternatives before moving over to the right
Decision Table
• Decision tables provide a way to examine, describe, and document decisions using a table
• They are used to– Describe the conditions– Identify possible decision alternatives– Indicate actions should be performed, and– Describe actions
Decision Tables• Decision tables help analysts ensure completeness
and accuracy• Four main problems that can occur in developing
decision tables– Incompleteness
– Impossible situations
– Contradictions
– Redundancy
Structured Charts Functional Decomposition (Divide and conquer) Information hiding Modularity Low coupling High internal cohesion
Structure Charts - Notation
Modules
Library modules
Module call
Data
Flag
Structure Charts
Input(Afferent Flow)
ProcessCentral Transform)
Output(Efferent Flow)
Input Process Output
Control
Multiple Choice Questions
Q. The relationship of data elements in a module is called(a) Coupling (b) Cohesion(c) Modularity (d) None of the above
Q. Which one is not a strategy for design?(a) Bottom up design (b) Top down design(c) Embedded design (d) Hybrid design
Q. A system that does not interact with external environment is called(a) Closed system (b) Logical system(c) Open system (d) Hierarchal system
Q. Which one is not a type of requirements?
(a) Known requirements(b) Unknown requirements(c) Undreamt requirements(d) Complex requirements
Q. Which one is not a requirements elicitation technique?
(a) Interviews(b) The use case approach(c) FAST(d) Data flow diagram
Q. Which is not a type of requirements under quality function deployment
(a) Normal requirements(b) Abnormal requirements(c) Expected requirements (d) Exciting requirements
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continues…
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