Lecture 15: Prototyping Data Dictionary Preliminary Design

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Lecture 15PrototypingData DictionaryPreliminar
y Design
MIS 160 Systems Development Life Cycle I
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Prototyping
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Definition

• A PROTOTYPE is a model of the system
• It can be as simple as mock-ups of reports or
  screens, or as complete as software that actually
  does some processing.
• Can be used as a communication tool between
  analyst and user.
• Prototyping is the process of developing
  prototypes.
• Prototyping strategy indicates the type of
  prototype used.

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How is it Used?

• As a methodology
• As a technique/tool within the SDLC.
• Some phases supported/replaced

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Approaches

• Type I - Iterative
• becomes final system
• Type II - Throwaway
• used as model for final system

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Type I (Iterative) Life Cycle
Requirements Definition
Prototype Training
Project Planning
Rapid Analysis
Database Design
Design Prototype
Generate Prototype
Test Prototype
No
Acceptable?
Yes
Implement System
Maintain System
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Type II (Throwaway) Life Cycle
Requirements Definition
Analysis
Design Prototype
Code Prototype
Test Prototype
No
Acceptable?
Yes
Code Final System
No
Test Final System
Implement Final System
Maintain Final System
Yes
Acceptable?
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Types of Prototypes

• Illustrative
• Mock-ups
• Simulated
• Looks like they work, but are simulations
• Functional
• Does some processing, but doesnt store data
• Evolutionary
• Used to produce an operational systems

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Prototype Levels

• Level 1 (Input-Output)
• printed reports and on-line screens
• screen flow sequence
• screen options
• Level 2 (Heuristic-Learning)
• updating database
• basic transactions

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Levels (Continued)

• Level 3 (Adaptive)
• working model of system
• system with training wheels
• no bells or whistles

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Advantages

• Speed
• Easier for end-users to learn
• System changes discovered earlier
• End-user involvement (ownership)
• increased user satisfaction
• increased user acceptance
• User-analyst communication
• Early problem detection
• reduced development time
• reduced maintenance

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Disadvantages

• Poor documentation
• Hard to control/manage
• (Unrealistic) User expectations
• time for final system
• final system differences
• reduced analysis

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Data Dictionary
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Data Dictionary Defined

• the data dictionary collects and coordinates
  specific data terms, and it confirms what each
  term means to different people in the
  organization.
• Kendall Kendall

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Data Dictionary(aka, Project Repository)

• Repository for all primitive-level data
  structures and data elements within a system.
• Use information from Class Diagram to create the
  DD
• DD details each of the attributes (data elements)

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Preliminary Design
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Moving to Design

• The purpose of the analysis phase is to figure
  out what the business needs. The purpose of the
  design phase is to figure out how to provide it.
• The steps in both analysis and design phases are
  highly interrelated and may require much iteration

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Design

• Analysis focuses on what a system is, what it
  must do and logical requirements
• Design converts functional models from analysis
  into models that represent the solution
• Design focuses on how the system will be built
• Structural components
• Target processing environment
• Determining levels of automation
• Requires less user involvement than analysis

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Understanding Design Elements

• Design is the process of describing, organizing,
  and structuring the components of a system at
  both the architectural level and at a detailed
  level
• Focused on construction
• Like developing blueprints

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Design Activities

• Designing the architecture of the system
• Modeling concurrent processes
• Designing user interfaces
• Identifying resusable classes and software
  components
• Mapping classes to constructs in the DBMS
• Designing mechanisms for handling errors
• Allocation of classes to source code and
  executable code components

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Combining Three Views

• Functional
• Users perspective of the system
• Static
• Structure of the system
• Dynamic
• Behavior of the system

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Analysis Objectives to Design Objectives
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OO Analysis Models to Design Models
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Major Components and Levels of Design

• System is first partitioned into major components
• Design activities usually proceed in parallel
• Design levels
• Architectural (high level)
• Detail level

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Partitions and Collaborations

• Creating subsystems or larger units
• Grouping units that collaborate
• May have collaboration among units or partitions
• The more messages or contracts between objects,
  the more likely they are in the same partition

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PACKAGES AND PACKAGE DIAGRAMS

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Package

• A general construct that groups units together
• a set of classes with shared relationships
• represents a subsystem
• Used to reduce complexity of models

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Package Diagrams

• Shows packages only
• Identifies major components of a system
• High-level diagram
• Determines final program partitions
• Dependencies determined

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Package Diagram Symbols
A PACKAGE Package A DEPENDENCY
RELATIONSHIP
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Dependency

• The structure and code in one package is
  dependent on another package.
• Indicates that a change in one package could
  cause a change to be required in another package.
• Example
• A change in one method will cause the interface
  for all objects of this class to change.
  Therefore, all classes that have objects that
  send messages to the instances of the modified
  class could have to be modified.

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Package Diagram of Appointment System
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Steps for Identifying Packages and Building
Package Diagrams

• Cluster classes together based on shared
  relationships
• Model clustered classes as a package
• Identify dependency relationships among packages
• Place dependency relationships between packages