CMS 370 Systems Analysis

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CMS 370- Systems Analysis

• Jacqueline A. Trent

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Objectives

• Analysis Phase
• Identify approaches/methods for requirements
  gathering
• Identify and create information system models
  including events tables, ER diagrams, class
  diagrams

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Class Outline

• Discussion of information gathering techniques
• Discussion and demonstration of modeling used for
  requirements gathering
• In-Class work on video store example

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Review

• System Scope Document
• Captures problem description, anticipated
  benefits, systems requirements to support
• Context Diagram
• Graphic picture of the scope of system
  identifying major players and information flow
• Project Schedule
• Depicts the work - start with SDLC phases then
  create tasks under each phase

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Analysis Phase in More DetailFigure 4-1
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Activities of the Analysis Phase and Key
QuestionsFigure 4-2

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Gather Information and Build Models Figure 4-5
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Observe and Document Business Processes

• Demonstrate work flows
• Create Activity Diagrams
• Functional Decomposition

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Activity Diagram SymbolsFigure 4-11
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Simple Activity DiagramFigure 4-12
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Define and Document Requirements

• System requirements all capabilities and
  constraints
• Functional requirements
• Activities the system must perform
• Based on procedures and business functions
• Documented in analysis models
• Technical requirements
• Describes operating environment or performance
  objectives
• Documented in narrative descriptions of technical
  requirements

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Validating and Prioritize Requirements

• Make sure gathered information is correct
• Structured walkthrough
• Effective means of implementing quality control
  early in project
• Verify and validate system requirements
• Review of findings from investigation and of
  models based on findings

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Modeling Requirements

• Analyst describes system requirements using a
  collection of models
• Complex systems require more than one type of
  model
• Models represent some aspect of the system being
  built
• Identify the events and things from gathered
  information

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Events and System Requirements

• Events
• Occurrences at a specific time and place
• Trigger all system processing
• Requirement definition
• Determine relevant events
• External events first
• Temporal events second
• Decompose system into manageable units

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Types of Events

• External
• Outside system
• Initiated by external agent or actor
• Temporal
• Occurs as result of reaching a point in time
• Based on system deadlines
• State
• Something inside system triggers need for
  processing

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Examples of Event Types Charge Account Processing
SystemFigure 5-6
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Create an Event TableFigure 5-14
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Video Store

• In-Class
• Create an Event Table based on your own
  experience

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Things and System Requirements

• What system information needs to be stored
• Outcomes
• Understanding of system
• Set of models

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Identify THINGS from Event Table

• Step 1 Identify all nouns about the system
• Step 2 Add items or categories of information
  needed
• Step 3 Refine list and record assumptions or
  issues to explore

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Characteristics of Things

• Relationship
• Naturally occurring association among specific
  things
• Occur in two directions
• Cardinality/multiplicity
• Binary, unary, ternary, n-ary
• Attribute
• One specific piece of information about a thing

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Relationships Naturally Occur Between
ThingsFigure 5-18
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Attributes and Values Figure 5-20
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Model Things Relationships

• Traditional Approach
• ER Diagrams
• Object Oriented Approach
• Class Diagrams

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Traditional ApproachThings called Data Entities

• Things the system needs to store data about in
  traditional IS approach
• Modeled with entity-relationship diagram
• Generally used with relational database
  development

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Traditional Approach Simple ERD
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Traditional Approach Cardinality Symbols of
Relationships
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Expanded ERD with Attributes ShownFigure 5-24
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Object-Oriented Approach Things called Objects

• Do the work in the system and store information
• Have behaviors and attributes
• Class Type of thing
• Object Specific thing
• Methods Behaviors of objects

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Object-Oriented Approach Basic Class Diagram

• Classes objects rather than data entities
• Generalization/specialization hierarchies
• General superclasses to specialized subclasses
• Inheritance allows subclasses to share
  characteristics of their superclasses
• Aggregation (whole-part hierarchies)
• Relates objects and its parts
• Defines object in terms of its parts

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Object-Oriented Approach Basic Class Symbol
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Object-Oriented Approach Generalization/Speciali
zation
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Object-Oriented Approach Aggregation or
Whole-Part Relationships
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Object-Oriented Approach Bank Account System
Class Diagram
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Video Store

• In-Class
• Identify things from Event Table based
• Create ERD or Class Diagram

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Summary

• Analysis Phase
• Identify functional and technical requirements
• Model requirements
• Narratives, reports, lists
• Diagrams and schematics
• Event tables
• ER Diagrams
• Class Diagrams

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Homework

• Assignment 3 Analysis your project
• Create/Obtain an activity diagram
• Create an Event table (p162)
• Create basic ER diagram(p175)
• Create a class diagram (p181)