Avoiding Pitfalls in Data Modeling - High-Performance Web Databases: Design, Development, and Deployment - page 298

Exhibit 18-20. Chart of pitfalls and remedies. ( continued )

Modeling
Areas

Considerations Remedies

• Semantics
• Completeness
• Technique

• Use semantics of relationship to see
whether redundancy occurs
• Use cardinality pattern as a clue
• Determine whether all business
questions can be answered without the
indirect relationship
• Examine and determine whether any
direct relationships have been missed

• Accuracy
• Semantics

• Review model for semantic soundness
with users
• Explore direct relationship first

• Semantics
• Completeness

• Create new relationship
• Delete or reword inconsistent
semantics

Entity
Subtypes

• Technique • Try orthogonal subtype

• Cut subtype hierarchy layer after
picking the most significant criteria first

• Technique
• Accuracy

• Try role entity concept
• Remodel with one supertype and
possibly multiple subtypes

• Completeness • Examine to see if supertype is needed

for the current and possibly future
applications

Role Entities • Technique

• Accuracy

• Apply generalization technique as
described

Time-Related
Situations

• Accuracy
• Semantics

• Review semantics of relationship
• Review cardinality in comparison with
semantics of relationship
• Validate the “time” requirement with
users

Cardinality • Semantics

• Completeness
• Accuracy

• Review with users on specificity and
validate with business questions
applied against the model

Associative
Entities

• Technique • Examine rules provided in article

Recursive
Relationship

• Technique
• Semantics

• Review and walk through

Normalization • Technique • Identify many entities as major or

minor, significant or less significant, as
early as possible
• Put attributes to right entities

Reference
(minor)
Entities
Attributes

• Technique
• Semantics

• Examine the cost of eliminating an
entity against future system
maintenance cost