Unit 1: Basic Data Processing Concepts

[cheatsheet1999]

Topic: Data Models

Levels of Abstraction

Many views, single conceptual (logical) schema and physical schema.

• Views describe how users see the data
• Conceptual schema defines the logical structure
• Physical schema describes the files and indexes used

Topic: Entity-Relationship Model (ER)

• Phase 1: Requirement Analysis
• Phase 2: Conceptual DB design
• Phase 3: Logical DB design

ER Model is used at Conceptual DB design

ER model Basics

• Entity: An entity is described using a set of attributes
• Entity set: A collection of similar entities, e.g. All employees
  - Entity set has a key
  - Each attribute has a domain
• Relationship: Association among 2 or more entities
• Relationship Set: Collection of similar relationships

Key Constriants

Each dept has AT MOST one manager, according to the Key constraint on Manages

Participation Constraints

• Does every department have a manager?
  • if yes, this is a participation constraint: the participation of Departments in Manages is said to be total(vs. partial)

Thin line: Key participation
Bold Line: At least once, participation constraint, total participation
Bold Line with an arrow: Exactly once

Weak Entities

• A weak entity can be identified uniquely only by considering the primary key of another (owner) entity.
  • Owner entity set and weak entity set must participate in a 1 : n relationship set. (One owner, many weak entities)
  • Weak entity set must have total participation in this identifying relationship set

Sum up

• Conceptual design follows requirements analysis
  • Yields a high-level description of data to be stored

Knowledge Check: Introduction to Big Data and Data Processing Systems

1. What kind of software should be used if one needs to store data online, make certain parts of it accessible by different user types, and searchable?

• Word processing software
• Spreadsheet software
• [Correct] Database management software (Database management software is designed to implement all of these tasks)
• Presentation software