lecture 4bw_210 css preparation in extra

helpful

1. MIS 210 Fall 2004
Lecture 4:
Data Modeling
Process Modeling
MIS 210
Information Systems I

2. MIS 210 Fall 2004
Data Models

3. MIS 210 Fall 2004Sylnovie Merchant, Ph. D.
Entity-Relationship Diagrams
•Data-oriented approach
–uses the data and the relationships among data
to model requirements
–purpose is to show the data used in the system
–good for modeling data stores from a DFD
•A representation of organizational data.
–Shows the rules about the meanings and
interrelationships among the data.

4. MIS 210 Fall 2004
E-R Diagrams
•Defined
–A graphical representation of an E-R model.
–E-R model
•a detailed, logical representation of the entities,
associations, and data elements for an organization
or business area.

5. MIS 210 Fall 2004
E-R Symbols
Entity
Attribute
Relationship

6. MIS 210 Fall 2004
Terminology
•Entity
–a “thing” in the real world
–has an independent existence
•Attribute(s)
–One specific piece of information about a thing
–a property of the entity
–has a value (or value set or domain)
•Cardinality
–the number of instances of an entity that are associated with
another entity
–a single occurrence of an entity

7. MIS 210 Fall 2004
Data Entities
An Entity is a thing the users need to know (i.e, record)
something about.

8. MIS 210 Fall 2004
Types of Things

9. MIS 210 Fall 2004
Types of Attributes
•Identifier (primary key / key attribute)
–An attribute (or attributes) selected as the unique,
identifying characteristic for an entity.
•Foreign Key
–An attribute (or attributes) in one database table
that is the primary key in another database table

10. MIS 210 Fall 2004
Attributes and Their Values
All videos/DVDs have the
following attributes:
Product ID number
Product Name
Product Description
Category ID
Supplier ID
Serial Number
Each video/DVD has a
value for each attribute:
1
Woodstock
Concert
Other
WRNRBR
DVD19925C1

11. MIS 210 Fall 2004
Relationships
•Relationship
–Naturally occurring association among specific
things
–Occur in two directions
–Cardinality/multiplicity

12. MIS 210 Fall 2004
Relationships
•Degree of Relationship
–number of entities that participate in that relationship
•Unary (recursive)
–degree one
–A relationship between instances of one entity.
•Binary
–degree two
–A relationship between instances of two entities
•Ternary
–A relationship between instances of three entities

13. MIS 210 Fall 2004
Cardinality of Relationships

14. MIS 210 Fall 2004
Relationships and Cardinality

15. MIS 210 Fall 2004
Trucking….One Approach
Truck
carries
Shipment
Warehouses
delivers to
stored at
Retail Stores
1
m
m
1
m
m
*Truck ID
Volume
Weight
*Shipment Number
Shipment Volume
Weight
Destination
Trips
makes1 m

16. MIS 210 Fall 2004
Trucking….Another Approach
Truck
carries
Shipment
Warehouses
delivers to
stored at
Retail Stores
1
m
m
1
m
m
Truck ID
Volume
Weight
Shipment Number
Shipment Volume
Weight
Destination
Trips
makes1 m

17. MIS 210 Fall 2004
Data Dictionary

18. MIS 210 Fall 2004
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

19. MIS 210 Fall 2004Sylnovie Merchant, Ph. D.
Data Dictionary
(aka, Project Repository)
•Repository for all primitive-level data structures
and data elements within a system.
•Use information from DFDs or ERDs to create the
DD
•DD details each of the data items, data flows,
processes, etc. in a system
•For example: DD entry for data items would
show characteristics such as size, type,
description, ranges, etc.

20. MIS 210 Fall 2004
Process Models

21. MIS 210 Fall 2004
Process Modeling
•Focus on the internal structure and
processes in the DFD
•Most popular models
–Structured English
–Decision Tables
–Decision Trees

22. MIS 210 Fall 2004
Structured English
•Form of English used to specify the
processes in a DFD
•Makes use of nouns and action verbs
•Similar to pseudocode

23. MIS 210 Fall 2004
Structured English Example
End of Month Processing
DO FOR EACH INVENTORY ITEM
COUNT STOCK IN STOCK ROOM
ENTER COUNT ON INVENTORY SHEET
END DO

24. MIS 210 Fall 2004
Decision Tables
•Lays out the logic of complex problems where
there are multiple actions based on multiple
decisions.
•Four components
–conditions
–decision rules
–actions
–action entries

25. MIS 210 Fall 2004
Decision Tables
•The total possible number of decision rules
represents the total possible combinations,
or permutations, of the condition values
•For example, for yes or no values:
number of decision rules = 2
n
•For three conditions with yes or no values
number of decision rules = 2
n
= 2
3
= 8

26. MIS 210 Fall 2004
Decision Tables
•For a range of values
–example, age: 1=18 to 20, 2=21-30, 3=31-40, 4=41-50,
5=50 or over
–five (5) values for this condition
•What if there are a combination of different values
–yes or no values
–five values
–total possible values = 2 x 5=10

27. MIS 210 Fall 2004
Decision Trees
•A graphical representation of a decision
structure.
•Difficult to use for a complex situation.