Ch 8 Exam 2

Provide an example of an Associative Entity.

A Certificate linking employees to completed courses.

Wat is a null candidate key?

A Null Candidate Key means that a candidate key can have empty (null) values for some entries. This is a problem because candidate keys are supposed to uniquely identify each record, and if a key is null, it can't serve this purpose.

Q: What is an associative class?

A: A class that models a relationship with its own attributes or operations, linking other classes.

What is a Candidate Key?

An attribute or combination of attributes uniquely identifying each entity instance.

wat is Candidate Key

An attribute uniquely identifying each entity instance

What is an Associative Entity?

An entity representing a many-to-many relationship with its own attributes.

wat is associative entity

Associative Entity: Entity type representing a many-to-many relationship.

Why should you avoid "intelligent" keys as identifiers?

Because they may contain information that could change, making them unreliable as a unique identifier.

Which relationship is the most common type of relationship encountered in data modeling?

Binary

wat are Business Rules

Business Rules: Preserve the integrity of the data model.

What are Attributes?

Characteristics or properties of an entity (e.g., student ID, name).

What are the rules for choosing an Identifier?

Choose a key that won't change over time. • Choose a key that will never be empty or null. • Avoid using "intelligent" keys (keys with built-in information). • Consider using a simple surrogate key for complex keys.

wat is composite attribute

Composite Attribute: Attribute with meaningful component parts.

What is Cardinality?

Defines how many instances of one entity relate to instances of another (e.g., one-to-many).

wat is derived attribute ?

Derived Attribute: Attribute whose value is computed from related attributes.

What is the difference between Disjoint and Overlap rules?

Disjoint: Supertype instance can only belong to one subtype.Overlap: Supertype instance can belong to multiple subtypes.

wat is Domain

Domain: Valid data types and values for an attribute.

What are Domains and Triggering Operations?

Domains: Constraints on valid attribute values.Triggering Operations: Rules that validate data manipulation, like checking withdrawal limits.

True or false: in an ER diagram, system outputs and relationships are the same as data flows from data flow diagrams

False

Ex of a candidate key

For example, in a list of employees, a candidate key could be something like an employee ID or a Social Security number.

What are Prepackaged Data Models?

Generic data models tailored for industries like healthcare or banking.

Ex of identifier

Identifier: Out of all candidate keys, the identifier is the one chosen to uniquely identify each instance of an entity. It's the main unique "tag" for each entry.

wat is multivalued attribute

Multivalued Attribute: An attribute with multiple values for an entity instance.

A unitary relationship is a relationship between the instances of ? entity types

One

wat is Optional Attribute

Optional Attribute: May or may not have a value.

wat is Partial Specialization Rule

Partial Specialization Rule: Not all supertype instances belong to a subtype.

wat is relationship

Relationship: Association between instances of one or more entities.

wat is repeating group

Repeating Group: Set of logically related multivalued attributes.

wat is a required attribute ?

Required Attribute: Must have a value for every instance.

wat is Identifier

Selected candidate key as the unique identifier for an entity.

True or false: a supertype is a generic entity type that has a relationship with one or more subtypes

True

Define Unary, Binary, and Ternary Relationships.

Unary: A relationship within one entity type.Binary: A relationship between two entities.Ternary: A relationship among three entities.

What is the Bottom-Up Approach to data modeling?

Utilizes business documents (reports, forms) to derive the data model.

If a purchase model is proven through extensive experience, it is said to be

Validated

List the benefits of using Prepackaged Data Models.

Validation, cost savings, adaptability, and completeness.

wat is Entity-Relationship Diagram (E-R Diagram)

Visual representation of an E-R model.

Cardinalities

Look at slides

What is the difference between Mandatory and Optional Participation?

Mandatory requires entity involvement, optional does not.

What is a Conceptual Data Model?

A detailed model that captures the overall structure of organizational data and is independent of any database management system.

What is a Supertype?

A generic entity type connected to one or more subtypes.

What is an Entity-Relationship Diagram (ERD)?

A graphical representation of a data model with entities as rectangles and relationships as lines.

What is a Subtype?

A more specific entity type within a supertype.

What is an Entity-Relationship (E-R) Model?

A structured, logical format representing entities, relationships, and attributes.

Define Entity Integrity and Referential Integrity.

Entity Integrity: Unique, non-null identifiers for entities.Referential Integrity: Rules governing relationships between entities.

Define Entity Type and Entity Instance.

Entity Type: A collection of similar entities.Entity Instance: A single occurrence of an entity.

What is a Repository used for in data modeling?

It stores all team work in a shared space to maintain links between data, processes, and logic models.

What are Business Rules?

Specifications that ensure the integrity of the logical data model.

wat is subtype

Subtype: Subgroup of entities within a supertype.

wat is supertype

Supertype: Generic entity type with relationships to subtypes.

What is the Top-Down Approach to data modeling?

The Top-Down Approach starts by examining the overall business goals, processes, and needs without looking at specific details or data sources (like forms or reports) right away. The idea is to define high-level entities and their relationships based on what is fundamental to the organization's operations.

Types of Relationships and Cardinality: What is Degree in relationships?

The number of entities involved in a relationship (unary, binary, ternary).

What is the purpose of a Conceptual Data Model?

To capture organizational data structure, supporting requirements analysis in information systems development.

Why must data elements in DFDs align with data models?

To ensure consistency between data flows and data stored in the system.

Why is it important to frame questions in Business Terms during information gathering?

To translate technical terms into language that engages stakeholders and meets business needs.

wat is total specialization rule

Total Specialization Rule: All supertype instances belong to a subtype.

Define the Total and Partial Specialization Rules.

Total: Each supertype instance must belong to a subtype.Partial: Supertype instances do not have to belong to a subtype.

wat is triggering operation (trigger)

Triggering Operation (Trigger): Rule governing data manipulation validity.

A(n) ________ is an assertion or rule that governs the validity of data manipulation operations such as insert, update, and delete.

Triggering operation