Midterm Review Flashcards
What are the basic building blocks of a data model?
Entities, attributes, relationships, and constraints.
What are the limitations of hierarchical data models?
Rigid tree structure, only supports one-to-many (no many-to-many), and low flexibility.
What is structured data and how is it different from unstructured data?
Structured: Organized (tables, defined schema).
Unstructured: Lacks fixed format (text, images).
How is a one to one relation enforced in a relational data model?
Use unique constraints/primary keys to ensure only one matching record in each table.
Each relation in the relational data model is a set.
True.
Hierarchical data models can model many to many relationships.
False. (They only support one-to-many relationships.)
Many to many relations show up frequently in modeling software requirements.
True.
Constraints are not part or the data model.
False. (Constraints are integral to enforcing data integrity.)
All relational database management systems guarantee that there will never be duplicates in a table.
False. (Duplicates can occur unless unique constraints are applied.)
The entity relationship model (ERM) is dependent on the database type.
False. (ERM is a conceptual design tool, independent of any DBMS.)
Prime attribute
An attribute that is part of a candidate key.
Attribute Domain
The set of allowable values for an attribute.
Super key
A set of attributes that uniquely identifies a record.
Weak Entity
An entity that cannot be uniquely identified by its own attributes; depends on another entity.
Existence Dependence
When a weak entity’s existence depends on a related strong entity.
Recursive Relationships
Relationships where an entity relates to itself.
Specialization Hierarchy
A structure that divides an entity into subtypes based on shared attributes.
ER Diagrams are specific to the RDBMS they are designed for.
False.
Explanation: They are conceptual models and independent of any specific DBMS.
An overlapping subtype relation is always a partial relation.
False.
Explanation: Overlapping subtypes can be total or partial depending on the business rules.
The completeness constraint can not be implemented in a relational database management system.
False.
Explanation: While not always natively supported, it can be enforced with triggers or application logic.
Define functional dependence.
A relationship where one attribute (or set of attributes) uniquely determines the value of another attribute.
