1. Conceptual Database Design
Chapter 8
Methodology -
Conceptual Database Design
Chapter 15 in Textbook

2. Database Design Hardware independent Software independent Conceptual
DB design
Hardware independent
Software dependent
Logical
DB design
Hardware dependent
Software dependent
Physical
DB design
Conceptual DB Design

3. Success Factors in Database Design
Work interactively with users as much as possible.
Follow a structured methodology throughout the data modelling process.
Employ a data-driven approach.
Incorporate structural and integrity considerations into the data models.
Combine conceptualization, normalization, and transaction validation techniques into the data modelling methodology.
Use diagrams to represent as much of the data models as possible.
Build a data dictionary to supplement the data model diagrams.
Be willing to repeat steps.
Conceptual DB Design

4. Design Methodology Overview
Step 1 Build local conceptual data model for each user view.
Step 2 Build and validate local logical data model for each view.
Step 3 Build and validate global logical data model.
Step 4 Translate global logical data model for target DBMS.
Step 5 Design physical representation.
Step 6 Design user views.
Step 7 Design security mechanisms.
Step 8 Consider the introduction of controlled redundancy.
Step 9 Monitor and tune the operational system.
Conceptual DB Design

5. Methodology Overview – Conceptual Database Design
Step 1 Build local conceptual data model for each user view
Step 1.1 Identify entity types.
Step 1.2 Identify relationship types.
Step 1.3 Identify and associate attributes with entity or relationship types.
Step 1.4 Determine attribute domains.
Step 1.5 Determine candidate and primary key attributes.
Step 1.6 Consider use of enhanced modeling concepts (optional step).
Step Check model for redundancy.
Step Validate local conceptual model against user transactions.
Step Review local conceptual data model with user.

6. Methodology Overview – Logical Database Design for Relational Model
Step 2 Build and validate local logical data model for each view
Step 2.1 Remove features not compatible with the relational model.
Step 2.2 Derive relations for local logical data model.
Step 2.3 Validate relations using normalization.
Step 2.4 Validate relations against user transactions.
Step 2.5 Define integrity constraints.
Step 2.6 Review local logical data model with user.
Conceptual DB Design

7. Methodology Overview – Logical Database Design for Relational Model
Step 3 Build and validate global logical data model
Step 3.1 Merge local logical data models into global model.
Step 3.2 Validate global logical data model.
Step 3.3 Check for future growth.
Step 3.4 Review global logical data model with users.
Conceptual DB Design

8. Methodology Overview – Physical Database Design for Relational Model
Step 4 Translate global logical data model for target DBMS
Step 4.1 Design base relations.
Step 4.2 Design representation of derived data.
Step 4.3 Design enterprise constraints.
Step 5 Design physical representation
Step 5.1 Analyze transactions.
Step 5.2 Choose file organization.
Step 5.3 Choose indexes.
Step 5.4 Estimate disk space requirements.

9. Methodology Overview – Physical Database Design for Relational Model
Step 6 Design user views
Step 7 Design security mechanisms
Step 8 Consider the introduction of controlled redundancy
Step 9 Monitor and tune the operational system
Conceptual DB Design

10. Step 1 Build Local Conceptual Data Model for Each View
Objective: To build a local conceptual data model of an enterprise for each specific view.
Step 1.1 Identify entity types
Objective: To identify the main entity types that are required by the view;
Document entity types in data dictionary.
Conceptual DB Design

11. Data Dictionary for Staff View Showing Description of Entities
Entity Name Description Aliases Occurrence
Staff General term describing all staff Employee Each member of staff works at one
employed by DearmHome particular branch
PropertyForRent General term describing all Property Each property has a single owner &
property for rent is available at one specific branch,
where the property is managed by 1
member of staff. A property is viewed
by many clients and rented by a single
client at a time
Conceptual DB Design

12. Step 1 Build Local Conceptual Data Model for Each View
Step 1.2 Identify relationship types
Objective: To identify the important relationships that exist between the entity types that have been identified.
Check for binary, complex, recursive relationship types.
Check for explicit, and implicit relationship types.
Use ER diagrams.
Determine multiplicity of relationships.
Check for fan and chasm traps.
Check that each entity participate in at least one relationship.
Document relationship type.
Conceptual DB Design

13. ERD for Staff View of DreamHome
supervisor
supervise
(0,*)
STAFF
register
BUSINESS
OWNER
supervisee
(0,*)
(0,*)
(1,*)
(0,100)
manage
BOwn
(0,1)
(1:1)
(0,1)
PROPERTY
views
CLIENT
(0,*)
(0,*)
POwn
(0,1)
(0,*)
(0,*)
(1:1)
associate
hold
state
(1,*)
(1:1)
(1:1)
PRIVATE
OWNER
LEASE
PREFERENCE
(1:1)

14. Data Dictionary for Staff View Showing Description of Relationships
Entity Name Multiplicity Relationship Entity Name Multiplicity
Staff Manages PropertyForRent
Supervises Staff
PropertyForRent AssociatedWith Lease *
Conceptual DB Design

15. Step 1 Build Local Conceptual Data Model for Each View
Step 1.3 Identify and associate attributes with entity or relationship types
Objective: To identify and associate attributes with the appropriate entity or relationship types and document the details of each attribute.
For entity list what information are we required to hold on?
Check simple & composite attributes.
Check single & multi-valued attributes.
Derived attributes.
Check for shared attributes.
Document the attribute.
Conceptual DB Design

16. Step 1 Build Local Conceptual Data Model for Each View
Step 1.4 Determine attribute domains
Objective: To determine domains for the attributes in the local conceptual model and document the details of each domain.
Data type.
Size.
Allowable value.
Default value.
Conceptual DB Design

17. Data Dictionary for Staff View Showing Description of Attributes
Entity Attribute Description Data Length Nulls Multi- Default Range PK
Name Type Valued Value
Staff StaffNo Uniquely identifies a staff member varchar No No Y
name
FName First name of Staff varchar No No
Lname Last name of Staff varchar No No
position Job title of member of staff varchar No No
sex Gender of member of staff character Yes No M F, M
DOB Date of Birth of member of staff Date Yes No
Conceptual DB Design

18. Step 1 Build Local Conceptual Data Model for Each View
Step 1.5 Determine candidate and primary key attributes
Objective: To identify the candidate key(s) for each entity and if there is more than one candidate key, to choose one to be the primary key.
CK must be:
minimal set of attributes.
least likely to have its value changed.
fewest size or smallest maximum number.
easiest to use from the user’s point of view.
Step 1.6 Consider use of enhanced modeling concepts
Objective: To consider the use of enhanced modeling concepts, such as specialization / generalization, aggregation, and composition.
Conceptual DB Design

19. ERD with PK supervise STAFF register BUSINESS OWNER manage BOwn
StaffNo
OwnerNo
supervisor
supervise
(0,*)
STAFF
register
BUSINESS
OWNER
supervisee
(0,*)
(0,*)
(1,*)
(0,100)
manage
PropertyNo
VDate
Comment
BOwn
(0,1)
(1:1)
(0,1)
PROPERTY
views
CLIENT
ClientNo
(0,*)
(0,*)
POwn
(0,1)
(0,*)
(0,*)
(1:1)
associate
hold
state
OwnerNo
(1,*)
(1:1)
(1:1)
PRIVATE
OWNER
LEASE
PREFERENCE
LeaseNo
(1:1)

20. EERD for Staff View of DreamHome
StaffNo
SUPERVISOR
STAFF
register
(0,*)
(0,100)
manage
OwnerNo
PropertyNo
VDate
Comment
(0,1)
(1:1)
(1,*)
(1,1)
PROPERTY
BOwn
views
CLIENT
OWNER
ClientNo
(0,*)
(0,*)
(0,*)
(0,*)
(1:1)
associate
hold d
state
PRIVATE
OWNER
BUSINESS
OWNER
(1:1)
(1:1)
LEASE
PREFERENCE
LeaseNo
(1:1)

21. Step 1 Build Local Conceptual Data Model for Each View
Step 1.7 Check model for redundancy
Objective: To check for the presence of any redundancy in the model.
1. Re-examine 1:1 relationships.
2. Remove redundant relationships.
Step 1.8 Validate local conceptual model against user transactions
Objective: To ensure that the local conceptual model supports the transactions required by the view.
Describe the transaction.
Use transaction pathways: diagrammatically represent the pathway taken by each transaction on the ERD.
Conceptual DB Design

22. Using transaction’s Pathways
StaffNo
(b)
SUPERVISOR
STAFF
register
(0,*)
(a)
(0,100)
(e)
(d)
manage
OwnerNo
PropertyNo
VDate
Comment
(c,g)
(0,1)
(1:1)
(1,*)
(1,1)
PROPERTY
BOwn
views
CLIENT
OWNER
ClientNo
(0,*)
(0,*)
(0,*)
(h,i)
(0,*)
(1:1)
associate
hold d
state
(m)
(l)
PRIVATE
OWNER
BUSINESS
OWNER
(1:1)
(j)
(1:1)
LEASE
PREFERENCE
LeaseNo
(1:1)
(k)

23. Step 1 Build Local Conceptual Data Model for Each View
Step1.9 Review local conceptual data model with user
Objective: To review the local conceptual data model with the user to ensure that the model is a ‘true’ representation of the user’s view of the enterprise.
Conceptual DB Design