Information Systems and Databases

Flashcards covering key vocabulary and concepts from the lecture notes on information systems, databases, SQL, and JSON.

Business Process

A sequence of business activities aimed at producing a product or service involving multiple resources (material, organizational, informational)

Information System

The set of components of an organization designed to acquire, process, store, retrieve, share, and transmit information

Computer System

Technology supporting the information system (hardware, software, databases, management system, communication networks)

Data

A representation of information useful for its storage and management

Information

Data that has been properly interpreted to give it meaning

Complex Information

Formed by elementary information, which is logically related to each other by associating appropriate semantics with the links

Basic Information

Meant to be as a triple of items: value, type, and attribute

Database

A set of information associated with collections of data, related to each other, and equipped with an appropriate description

Metadata

Data describing other data

DBMS (Database Management System)

Set of programs that allows to define, manipulate, and check data within a database

ANSI-SPARC Three-Level Architecture

Proposed to ensure strict isolation between the data and the programs/applications that operate on them using layered definitions

Logical Data Independence

Applications are independent of the way the data are logically organized

Physical Data Independence

Applications are guaranteed by the different physical implementations of the data

Hierarchical Model

Data are organized into hierarchies through the use of tree-like data structures

Reticular Model

Data are organized in a lattice through the use of graph data structures

Relational Model

Data are organized in relationships, that is, a set of records having the same logical structure

Object-Oriented Model

Data are organized in the form of software “objects” and links between them

Object-Relational Model

The model remains relational (table structure) but the table structure is generalized in order to contain objects as well as elementary values

NoSQL Models

Alternative models to the relational model, introduced for the efficient management of large volumes of data from heterogeneous sources with high variability

Transactions

The DBMS executes particular programs called transactions

Transaction

The execution of a user program in a DBMS environment that syntactically and semantically constitutes an atomic unit of persistent changes made to the database

Atomicity

A transaction is executed in its entirety or not at all

Consistency

A transaction transforms the database from one consistent state to another

Isolation

Transactions are executed independently of each other; partial effects are not visible to other transactions

Durability

The effects of a committed transaction are permanently recorded in the database and never lost

Access Manager

Module of a DBMS that performs database access control

Query Manager

Component that handles user requests in terms of DDL and DML operations

Memory Manager

Component responsible for defining strategies for accessing information in mass memory and its transfers

File Manager

Module that deals with management of files on mass storage

Integrity Manager

Module responsible for verifying that integrity rules are verified within the database

Concurrency Control Manager

Module that aims to manage concurrent transaction access to shared database resources

Reliability Manager

Module that deals with saving operations on the database in log files and initiating procedures to restore the database itself downstream of failures

Operational Support System

System that is related to daily operations

Relation on a Schema

A relation on a relation schema r(X) is defined as an instance of r(X)

Integrity Constraint

A rule that every instance of a relation schema must adhere to in order for its data to match the model of reality that a database captures

Intra-relational Constraints

Rules involving a single relation a. on the values of an attribute (domain constraints) b. on multiple attributes of the tuple (tuple constraints) They affect all tuples, one independently of the others c. of key (for unique identification of a tuple)

Inter-relational Constraints

constraints involving multiple relations: a. allow to check the validity of attribute values entered in one relation to relate it to another.

Domain Constraint

A rule that must be satisfied by the values of a fixed attribute of a relation

Tuple Constraint

A logical condition involving multiple attributes within the same tuple

Structured Query Language

SQL stands for?

Create Table

Used to create a new relation: in it you specify: - the name of the relation - the name and type of its attributes - intra- and inter-relational constraints

Data Manipulation Language (DML)

SQL as?

Aggregate operators

Operate not at the tuple level but at the relation level

JSON

It stands for JavaScript Object Notation

Syntax

Unordered sets of name / value pairs Begins with {(leftbrace) Ends with }(rightbrace) Each name is followed by : (colon) Name/value pairs are separated by , (comma)