Chapter 3: Data Models Flashcards

Flashcards covering the definition, importance, evolution, and components of data models, including business rules, relational concepts, and abstraction levels.

What is a data model?

A representation, usually graphical, of a real-world data structure.

What is the process of data modeling?

Creating a specific data model for a problem to determine what data and relationships should be stored in the database.

What are the two major data models used today?

Entity-Relationship Model (ERD) and Class Diagram (Object-Oriented).

What is a business rule?

A brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization.

How do business rules translate into data model components?

Nouns translate into entities, and verbs that associate nouns translate into relationships.

What are the characteristics of the Hierarchical Model?

It is based on an upside-down tree structure where each parent can have many children, but each child has only one parent.

How does the Network Model differ from the Hierarchical Model regarding parents?

Unlike the hierarchical model, the network model allows a record to have more than one parent.

What standard database concepts emerged from the Network Model and are still used today?

Schema, subschema, DML, and DDL.

Defining components of the Relational Model, what are relations, tuples, and attributes?

A relation is a table; a tuple (or record) is a row; and an attribute is a column.

What is a major advantage of the Relational Model over previous file-based systems?

It yields complete data and structural independence because it is a purely logical structure.

According to the notes, what should an entity NOT be?

A user of the database system or an output of the database system (such as a report).

What is the definition of an attribute?

A characteristic, data field, or data element of an entity.

What is Crow’s Foot Notation used for?

To describe the cardinality of relationships (minimum and maximum entity occurrences) between two entities.

How are many-to-many ($M:N$) relationships resolved in a relational database?

They are split into two pairs of $1:M$ relationships by introducing an associative entity (also known as a weak entity).

Define the three degrees of relationships: Unary, Binary, and Ternary.

Unary involves a single entity; Binary involves two entities; Ternary involves three entities.

What is encapsulation in the Object-Oriented Model?

Incorporating both data and functions into a unit where they are protected from outside modification.

What is inheritance in an Object-Oriented Data Model?

The ability of an object within the class hierarchy to inherit the attributes and methods of classes above it.

Name the three levels of data abstraction in a DBMS.

1. Physical Level (Internal Level), 2. Logical Level (Conceptual Level), 3. View Level (External Level).

What are the primary features of a Conceptual Data Model?

It includes important entities and relationships but specifies no attributes and no primary keys.

What is the difference between software independence and hardware independence in data modeling?

Software independence means the model does not depend on the DBMS software; hardware independence means it does not depend on the physical hardware used.

What is a data dictionary?

A detailed description of all tables in the database which contains at least all attribute names and characteristics; it contains metadata.

What is metadata?

Data about data.