1. COS 346
Day 3

2. Agenda Questions from last Class? Assignment 31 Graded
2 A’s, 1 B, 1 C, 2 F’s and 1 non-submit
Some of you need to take these assignments more seriously
Assignment #2 Due next class
Assignment # 3 will be assigned next class
First Exam
Feb2 one week from today
Chaps 1-3
20 M/C; 5 Short essays
60 min WebCt
Today’s discussion
Entity-Relationship Data Modeling: Process and Examples
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3. Chapter 3 Entity-Relationship Data Modeling: Process and Examples

4. Quick review of E-R
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5. Quick review of IDEF1X Question 2.76 on page 69 of text P
FISH
OBSERVATION
RIVER
OBSERVER
CLASS
CLASS_OFFERING
PROFESSIONAL
VOLUNTEER
RIVER_SITE P
Question 2.76 on page 69 of text
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6. A Data Modeling Process
Steps in the data modeling process
Plan project
Determine requirements
Specify entities
Specify relationships
Determine identifiers
Specify attributes
Specify domains
Validate model
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7. Planning the Project Obtaining project authorization and budget
Building the project team
Planning the team’s activities
Establishing tools, techniques, and standards for consistent results
Defining the project’s scope
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8. Determining System Requirements
Sources for data modeling requirements
User interviews and user activity observations
Existing forms and reports
New forms and reports
Existing manual files
Existing computer files/databases
Formally defined interfaces (XML)
Domain expertise
The result of the requirements determination will be a repository of notes, diagram, forms reports, files, etc., that can be used to develop the data model
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9. Specifying Entities
An entity is something that the users want to track; something the users want to keep data about
Entities
can be physical things or logical concepts
are identifiable; you can tell one from another
are things described by nouns, not characteristics described by adjectives
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10. Specifying entities
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11. Specifying Relationships
Includes:
Identity of the parent and child entities
Relationship type
Minimum and maximum cardinalities
Name of the relationships
Two techniques:
Examine whether a relationship exists between every combination of two entities
Locate relationships from requirement documents
A combination of the two approaches may be used
Be careful of combinatorial explosions
5 entities -> 20 possible relationships to explore
10 entities -> 90 possible relationships to explore
100 entities -> 9900 possible relationships to explore
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12. Specifying Relationships
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13. Determining Identifiers
Identifier is an attribute or group of attributes that uniquely identifies an entity instance
If there is difficulty specifying an identifier, maybe:
it should be part of a different entity
it is a subtype or category of a common entity
it needs one or more identifying relationships
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14. COS 346
Day 4

15. Agenda Questions from last Class? Assignment # 2 Due
Assignment # 3 Posted
First Exam
Feb 9
Chaps 1-3
20 M/C; 5 Short essays
60 min WebCt
Capstone Projects
Today’s discussion
Entity-Relationship Data Modeling: Process and Examples
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16. Capstone Projects Students choice of projects
Since this class is on Databases, Project must be in this area
Student must go beyond the curriculum of the course
Student defined deliverables
Must have a in-class presentation of project using PowerPoint
Accepted proposal due by February 9
Progress reports required
Guidelines
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17. Specifying Attributes and Domains
Find attributes on forms, reports, existing files, etc., and add them to entities
Determine whether the attribute has already defined a domain
If so, the attribute is based upon that domain
If not, a new domain is defined
Review the domains and make adjustments as necessary
Domain property inheritance: when the domain properties change, all the attribute properties change as well
Domains may be used to enforce data standards promoting compatible data types and systems
Important for “joins”
Start of a data dictionary
Once all attributes have been specified the model should be reviewed for missing entities
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18. Validating Model
Data model is a model of humans’ models, not a model of reality
A data model is wrong if it does not accurately reflect the ways the users think about their world
Data models are validated through a series of reviews
Normally, a team review is followed by user reviews
E-R model as well as prototypes of forms and reports may be used to communicate to users features of the data model
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19. Creating Data Models From Forms and Reports
Example: Single entities
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20. Example: Identifying Connection Relationships
Cardinality? P, 1, Z
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21. Example: Repeating Groups
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22. Example: Repeating Groups
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23. Example: Nested Groups
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24. Example: Non-Identifying Connection Relationships
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25. Example: Non-Identifying Connection Relationships
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26. Example: 1:N
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27. Example: 1:N
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28. Example: 1:N
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29. Non-specific (N:M) Relationship
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30. Example: N:M
Insert
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31. Example: Assignment Relationship
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32. Example: Assignment Relationship
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33. Example
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34. Example
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35. Example
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36. Example: Category Relationship
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37. Example: Category Relationship
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38. Example: Category Relationship
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39. Sales-Order Model
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40. Example: Sales Order
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41. Example: Sales Order
Figure 3-16(c) shows an alternative design that allows an item to appear more than once on a given order
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42. College Report
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43. Department/Professor Report
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44. Choice 1
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45. Choice 2
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46. Choice 3
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47. Choice 4
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48. Department/Major Report
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49. Adding Student Entity
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50. Advisee Letter
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51. Adding Advisors & More Student Info
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52. University System With Domain Names
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53. Assignment #3 Problem 3.44 FiredUp Project Questions
Data modeling exercise
Important stuff
FiredUp Project Questions
I will have corrected version back to you this weekend
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54. Chapter 3 Entity-Relationship Data Modeling: Process and Examples