Conceptual Design Flashcards
Designing E/R
What is reification in E/R modeling?
Reification is converting a complex relationship with attributes into an entity for better representation.
How do you decide if a concept should be an entity or an attribute?
If it has signficant properties or standalone existence, it should be an entity
Its important to not model instances as
entities
5 qualities of a good conceptual schema
Correctness, completeness, minimality, pertinence and readability
What does minimality in a conceptual schema mean?
No redundant concepts
How do you ensure pertinence in a conceptual schema?
Excluding unnecessary elements that do not contribute to meeting the requirements
Main steps in gathering requirements for database design
- Building a glossary
- Clarifying amiguities
- Grouping homogeneous requirements
- Separating data from functional needs
Why is glossary important
Avoid misinterpretation
What is a skeleton schema?
Basic framework that includes only most relevant concepts to guide further integration and refinement
What is the iterative step in E/R design methodology?
Refining and adding concepts based on detailed requirements until the schema is satisfactory
Why should “book” and “book copy” be modeled separately?
Library database
Differentiate between the abstract concept of a book (its author,publisher,etc) and its physical instance or copies
How is the MARRIAGE relationship handled in E/R design
Reifying it into an entity to handle attributes like data and ensure constraints (no duplicate marriages on the same day)
Remember, if a relationship has attributes or it is a many to many, or it requires precise representation like a VISIT then we should make an entity
