Transcript MidtermReview

Midterm Review
Information System Design
Topics Covered
 Chpt 8: Process Modeling
 Chpt 9: Feasibility Analysis
 Chpt 10: Systems Design
 Chpt 12: Database Design
Process Modeling
Test Design
 Closed book. No calculators or notes.
 True/False questions (20 pts)
 Short answer (50 pts)
 Two designing/modeling questions (30
pts)
A model is a representation of reality. Just as a
picture is worth a thousand words, most models are
pictorial representations of reality.
Logical models show
what a system is or
does. They are
implementation
independent; that is,
they depict the system
independent of any
technical
implementation.
Physical models show
not only what a system is
or does, but also how the
system is (to be)
physically and
technically implemented.
They are implementation
dependent because they
reflect technology
choices.
Decomposition is the act of breaking a system into its
component subsystems, processes, and subprocesses.
Each level of abstraction reveals more or less detail.
System Decomposition
Other Process Modeling
Topics
 Data Flow Diagrams
 Structured English
 Decision Tables
 Data packets
 Legal and illegal data flows
 Data structures, data types and domains
 Diverging and converging data flows
 External agents, data stores
 Use cases
 Data to Process CRUD Matrix
Data Flows and Control Flows
 A data flow represents an input of data to a
process, or the output of data from a process.

A data flow may also be used to represent the
creation, reading, deletion, or updating of data in a
file or database (called a data store).

A composite data flow is a data flow that consists of
other data flows.
 A control flow represents a condition or
nondata event that triggers a process.

Used sparingly on DFDs.
Feasibility Analysis
Four Feasibility Tests
 Operational feasibility is a measure of how
well the solution will work in the organization.
It is also a measure of how people feel about
the system/project.
 Technical feasibility is a measure of the
practicality of a specific technical solution and
the availability of technical resources and
expertise.
 Schedule feasibility is a measure of how
reasonable the project timetable is.
 Economic feasibility is a measure of the
cost-effectiveness of a project or solution.
Cost/Benefit Analysis
Costs:
 Development costs are one time costs that will not recur after
the project has been completed.
 Operating costs are costs that tend to recur throughout the
lifetime of the system. Such costs can be classified as:
Fixed costs — occur at regular intervals but at relatively fixed rates.
 Variable costs — occur in proportion to some usage factor.

Benefits:
 Tangible benefits are those that can be easily quantified.
 Intangible benefits are those benefits believed to be difficult or
impossible to quantify.
Three Ways to Approach
Cost/Benefit Analysis
 Payback Analysis
 Return On Investment
 Net Present Value
The Time Value of Money is a concept that should be
applied to each technique. The time value of money
recognizes that a dollar today is worth more than a dollar
one year from now.
Candidate System Matrices
Feasibility Analysis Matrix
Feasibility Analysis Matrix is intended
to complement the candidate systems
matrix with an analysis and ranking of
the candidate systems.
Candidate 1 Name Candidate 2 Name Candidate 3 Name
Description
Operational
Feasibility
Technical
Feasibility
Schedule
Feasibility
Economic
Feasibility
Ranking
System Design
System Design Approaches
 Model-Driven
 Modern
structured design
 Information engineering
 Prototyping
 Object-oriented
 JAD
 RAD
Modern Structured Design
A process-oriented technique for breaking
up a large program into a hierarchy of
modules that result in a computer
program that is easier to implement and
maintain (change). Synonyms (although
technically inaccurate) are top-down
program design and structured
programming.
Information Engineering
A model-driven and data-centered, but
process-sensitive technique to plan,
analyze, and design information
systems.
The primary tool of IE is a data model
diagram.
Prototyping and Obj. Oriented
 The prototyping approach is an iterative

process involving a close working relationship
between the designer and the users.
Object-oriented design (OOD) techniques
are used to refine the object requirements
definitions identified earlier during analysis,
and to define design specific objects.
RAD and JAD
Rapid application development (RAD) is the merger
of various structured techniques (especially the datadriven information engineering) with prototyping
techniques and joint application development
techniques to accelerate systems development. RAD
calls for the interactive use of structured techniques
and prototyping to define the users’ requirements and
design the final system.
Joint Application Development (JAD) is a technique
that complements other systems analysis and design
techniques by emphasizing participative development
among system owners, users, designers, and
builders.
Database Design
Files and Databases
A file is a collection of similar records.
A database is a collection of
interrelated files (meaning that records
in one file are physically related to
records in another file).
A field is the physical implementation of a data
attribute. They are the smallest unit of
meaningful data.
A primary key is a field
whose values identify
one and only one record
in a file.
A secondary key is an
alternate identifier for a
record.
A foreign key is a
pointer to a record in a
different file.
A descriptive field is
any other (nonkey) field
that stores business
data.
Relational databases
implement stored data in a series of twodimensional tables that are “related” to one
another via foreign keys.




The physical data model is called a schema.
The DDL and DML for a relational database is
called SQL (Structured Query Language).
Triggers are programs embedded within a table
that are automatically invoked by updates to
another table.
Stored procedures are programs embedded
within a table that can be called from an
application program.
Data Normalization
 An logical entity (or physical table) is in first normal
form if there are no attributes (fields) that can have
more than one value for a single instance (record).
 An logical entity (or physical table) is in second
normal form if it is already in first normal form and if
the values of all nonprimary key attributes are
dependent on the full primary key.
 An logical entity (or physical table) is in third normal
form if it is already in second normal form and if the
values of all nonprimary key attributes are not
dependent on other nonprimary key attributes
Database Goals
 A database should provide for efficient
storage, update, and retrieval of data.
 A database should be reliable—the stored
data should have high integrity and promote
user trust in that data.
 A database should be adaptable and scalable
to new and unforeseen requirements and
applications
Study Hard!
Good Luck!