Lecture 1

Question 1

Database

Answer 1

Information that is organised so that is easily accessed, managed and updated.

Question 2

DBMS

Answer 2

Handles the storage, retrieval, and updating of data in a computer system (it’s software).

Question 3

Generations of Database Systems

Answer 3

First-generation — Hierarchical, Network

Second generation — Relational

Third generation — Object-Relational, Object-Oriented

Question 4

Relational databases

Answer 4

• data stored in predefined tables
  
  • rows and columns
• attributes in a relation are called a domain
• the model also accounts for the types of relationship between those tables, including 1:1, 1:M, M:M
• a particular attribute (or combination of attributes) is chosen as a Primary Key that can be referred to in other tables, and in this case it’s called a Foreign Key
• tabels can be normalized
• typically written in SQL

Question 5

Flat file

Answer 5

a single table (.csv files)

Question 6

Hierarchical

Answer 6

• parent-child tree
• usually XLM
• cons
  
  • no M:M; each child in the tree may only have one parent
  • relationships or linages between children are not permitted
  • adding a new field or record requires that the entire database is redefined
• pros
  
  • can be accessed and updated rapidly
  • great for storing items that describe attributes

Question 7

Network

Answer 7

• similar to hierarchical, but a child can have multiple parents
• allows M:M
• uses SQL for data manipulation

Question 8

Object oriented

Answer 8

• an object can be a table, but it is not limited to being a table only
• stores objects as they programmed, without the need of conversion or decomposition, also maintaining relationships (e.g., inheritance)
• databases follow an object oriented data model with classes, properties and methods
• an object is always managed as a whole; system enables data and its attribute to function as a single unit
• this means for example, that the insertion of an object, which in a relational system would probably be stored in multiple tables, will be performed automatically as one atomic transaction — without any action by the application program; reading an object can also be done as a single operation and without complex joins.
• based on the function that data and its concerning object are treated as a single unit

Question 9

object-relational database

Answer 9

only allows data to be in tables, no other data type/structure

Question 10

Graph

Answer 10

• NoSQL databases
• use a graph structure for semantic queries
• data is stored in form of nodes, edges, and properties
  
  • a node represent an entity or instance such as customer, person, or a car (a node is equivalent to a record in a relational database system)
  • an edge in a graph database represents a relationship that connects nodes
  • properties are additional information added to the nodes.

With a vast amount of data, the patterns and connections in data become as important as the data itself.

Question 11

vertical prototyping vs. horizontal prototyping

Answer 11

Vertical prototype

Function-based. Used in the later stages of analysis and design to drill down and elaborate on specific features or functions.

Horizontal Prototypes

Give a broad view of the application.

Question 12

entity-relations model

Answer 12

• E-R Model can be expressed as the collection of entities, also called as realword objects and relations between those entities
• No two entities should be identical

E-R model deals with entities and their relations

Relational Model deals with tables and relation between the data of those tables