Information Management (Chapter 2)

Data modeling

It is the first step in designing a database, refers to the process of creating a specific data model for a determined problem domain

Data model

It is a relatively simple representation, usually graphical, of more complex real-world data structures

Entity

It is a person, place, thing, or event about which data can be stored

Attribute

It is a characteristic of an entity or object. An attribute has a name and a data type

Relationship

An association between entities.

Constraint

A restriction placed on data, usually expressed in the form of rules.

Business rule

A description of a policy, procedure, or principle within an organization

Naming Conventions

Entity names should be descriptive of the objects in the business environment and use terminology that is familiar to the users. An attribute name should also be descriptive of the data represented by that attribute. It is also a good practice to prefix the name of an attribute with the name or abbreviation of the entity in which it occurs.

Relational Model

Developed by E. F. Codd of IBM in 1970, the relational model is based on mathematical set theory and represents data as independent relations.

Table (relation)

A logical construct perceived to be a two-dimensional structure composed of intersecting rows (entities) and columns (attributes) that represents an entity set in the relational model.

Tuple

In the relational model, a table row

Table (Relational Model)

Each column represents an attribute. The relational model also describes a precise set of data manipulation constructs based on advanced mathematical concepts

Relational database management system (RDBMS)

A collection of programs that manages a relational database. The RDBMS software translates a user’s logical requests (queries) into commands that physically locate and retrieve the requested data.

Relational diagram

It is a representation of the relational database’s entities, the attributes within those entities, and the relationships between those entities

Entity relationship (ER) model (ERM)

A data model that describes relationships (1:1, 1:M, and M:N) among entities at the conceptual level with the help of ER diagrams.

Entity (ERD)

An entity is represented by a rectangle, also known as an entity box. The name of the entity, a noun, is written in the center of the rectangle. The entity name is generally written in capital letters and in singular form

Relationships(ERM)

It describes associations among data. Most relationships describe associations between two entities.

ER Notation

Chen notation,Crow’s Foot notation, Class diagram notation

External model

The application programmer’s view of the data environment. Given its business focus, an external model works with a data subset of the global database schema.

External schema

The specific representation of an external view; the end user’s view of the data environment

Conceptual model

It represents a global view of the entire database by the entire organization. That is, the conceptual model integrates all external views (entities, relationships, constraints, and processes) into a single global view of the data in the enterprise

Conceptual schema

A representation of the conceptual model, usually expressed graphically.

Software independence

A property of any model or application that does not depend on the software used to implement it.

Hardware independence

A condition in which a model does not depend on the hardware used in the model’s implementation. Therefore, changes in the hardware will have no effect on the database design at the conceptual level.

Logical design

A stage in the design phase that matches the conceptual design to the requirements of the selected DBMS and is therefore software dependent.

Internal model

In database modeling, a level of data abstraction that adapts the conceptual model to a specific DBMS model for implementation. The internal model is the representation of a database as “seen” by the DBMS. In other words, the internal model requires a designer to match the conceptual model’s characteristics and constraints to those of the selected implementation model.

Internal schema

A representation of an internal model using the database constructs supported by the chosen database.

Logical independence

A condition in which the internal model can be changed without affecting the conceptual model

Physical model

A model in which physical characteristics such as location, path, and format are described for the data. The physical model is both hardware- and software-dependent.

Physical independence

A condition in which the physical model can be changed without affecting the internal model.