Instructor NotesModule4:Derivinga
Logical DataDesign
Introduction
This module provides an in-depth discussion of logicaldata design. Students
examine the relationship of logicaldatadesign to conceptual design. Logical
entities, their attributes, and the relationships among them are extensively
examined. Finally, students learn how to create alogicaldata model from
entities, attributes, and relationships.
After completing this module, students will be able to:
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Analyze data requirements to determine data entities and attributes.
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Analyze data entities and attributes to determine their relationships.
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Determine the cardinality and existence characteristics of a relationship.
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Create an entity/relationship diagram.
Materials and Preparation
This section provides you with the materials and preparation needed to teach
this module.
Materials
To teach this module, you will need the following materials:
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Microsoft
®
PowerPoint
®
file P04_1609a.ppt
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Module 4, “Deriving aLogicalData Design”
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Activity 4.1, “Deriving Entities and Attributes from Data Requirements”
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Activity 4.2, “Creating aLogicalData Model”
Preparation
To prepare for this module, you should:
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Read all materials for this module.
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Complete the activities.
Presentation:
90 Minutes
Activities:
45 Minutes
2 InstructorNotesModule4:DerivingaLogicalDataDesign
Activities
Activity 4.1: Deriving Entities and Attributes from Data
Requirements
This activity provides students with a real-world example of use case
requirements that they will analyze to identify entities, attributes, and
relationships.
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Students will work individually on the first exercise to identify entities.
After the first exercise, you should lead a class discussion so that students
can come to a consensus about the entities.
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In the second exercise, assign students to small groups and give each group
two entities. Each group will identify attributes for their entities. Have
groups list their attributes on flip charts that they will share with the class
when they are done. At the end of the exercise, lead a class discussion so
that students can come to a consensus about the attributes for each entity.
Do not show students the answers on the Student CD until the end of
class. No absolute right answers apply to this activity, and students will
learn more by discussing the merits of various answers.
After completing this activity, students will be able to:
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Identify and derive data entities from use cases.
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Identify attributes of the derived data entities.
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To prepare for the activity
1. Have one flip chart and a set of markers ready for each group of students.
2. Complete both exercises in the activity. Try to anticipate all the alternative
answers that the students might derive.
Activity 4.2: Creating aLogicalData Model
In this activity, students identify relationships between entities, and then
identify the cardinality and existence characteristics of the relationships.
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Assign students to small groups and have them create an ER diagram with
labeled relationships. Then lead a class discussion so that students can come
to a consensus about the relationships.
After completing this activity, students will be able to:
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Identify relationships between entities.
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Create alogicaldata model.
Note
InstructorNotesModule4:DerivingaLogicalDataDesign 3
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To prepare for the activity
1. Complete both exercises in the activity.
2. Be sure you can explain the solution ER diagram.
Do not show students the answers on the Student CD until the end of
class. No absolute right answers apply to this activity, and students will
learn more by discussing the different diagrams they have created.
Module Strategy
Use the following strategy to present this module:
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Logical DataDesign
This section introduces the concept of logicaldata design. For many
students, this concept will be new and somewhat challenging. Either they
will never have thought logically about data at all, or they will have
proceeded directly to the physical (table) design phase, skipping the logical
phase. Your primary task as instructor is to convince all students of the
value and necessity of logicaldata design. In this section, you must explain
the benefits of conducting logicaldatadesign before physical design.
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Entities and Attributes
This section introduces the building blocks of the logicaldata model:
entities and their attributes. The experienced database designers in your
class will begin to tie entities to rows and attributes to columns and will
grasp these concepts fairly quickly. Be careful not to move so rapidly that
you leave behind students without such experience. Also challenge the class
to look for all entities and attributes, not just obvious ones. Brainstorming
can often aid in the search. Note that, at this point, the listing of attributes is
not tied to normalization and does not include keys; both are discussed later
in the course.
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Data Relationships
This section introduces the concept of relationships and of using verbs to
describe them. More experienced students might want to jump into defining
foreign keys; keep them focused on the implications of their choice of verbs
now for later design phases. Help all students to see the importance of
capturing an accurate linguistic description of the entity, its attributes, and
its relationships to other entities, because these aspects will form the basis
for the final physical model.
Although the concepts of cardinality and existence are fairly simple, they
are the keys to later development of the physical design because they affect
both normalization and the data model. Be sure to have numerous
supplementary examples as backup for the examples in the text, in case less-
experienced students do not grasp the concepts the first time you teach
them.
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Entity/Relationship Modeling
The groundwork laid in the earlier sections is put to use to create the logical
data model. If students have understood the earlier sections thoroughly, this
section should proceed easily. Watch for facial expressions or other
reactions that might indicate a lack of understanding, and be sure to
ascertain the level of understanding throughout the class during the activity.
Note
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Instructor Notes Module 4: Deriving a
Logical Data Design
Introduction
This module provides an in-depth discussion of logical data design. Students. be able to:
!
Analyze data requirements to determine data entities and attributes.
!
Analyze data entities and attributes to determine their relationships.