Databases: Definitions & Metadata

Basic Definitions

• Data refers to recorded facts that can be accessed and have an implicit meaning
• Data formats include text, numbers, figures, graphics, images, and audio/video recordings
• Data is typically kept because it is considered useful to an intended user
• Information refers to data that is accessed by a user for a specific purpose
• Obtaining needed information often requires activities like searching, processing, or manipulating data

Database

• A structured collection of related data stored on a computer medium
• Data is organized for efficient access to information
• Database Management System (DBMS): software for creating, inserting, storing, retrieving, updating, and deleting data
• It also maintains databases
• Database system: a computer-based system facilitating interaction between users and information
• It comprises the DBMS software and the data itself, sometimes including related applications

Database Metadata

• A DBMS catalog stores a description of a particular database called meta-data with data structures, types, and constraints
• Database metadata represents the structure, including database content that's not the data itself
• It contains names of data structures, data types and descriptions, and other characterization information
• Metadata describes the structure and properties of data and is essential for understanding and using the data properly

Database Schema vs State

• Database Schema includes descriptions of structure, data types, and constraints, and is also called the intension
• It changes infrequently
• Database State refers to the database content at a specific moment, also known as instance/occurrence/snapshot/extension
• It changes with every update
• Valid State: a state that satisfies the structure and constraints

DBMS Languages

• Data Definition Language (DDL) is used by database administrators and designers to specify a database's conceptual schema
• DDL is used to define internal and external schemas
• Data Manipulation Language (DML) is used to specify database retrievals and updates
• Stand-alone DML commands can be applied as a query language

Typical DBMS Functionality

• Define a database in terms of its data types, structures, and constraints
• Construct or Load the initial database contents onto a secondary storage medium
• Manipulating the database
• Retrieval: querying and generating reports
• Modification: Insertions, deletions, and updates to its content
• Accessing the database through Web applications
• Processing and Sharing by a set of concurrent users and application programs
• It keeps all data valid and consistent

Additional DBMS Functionality

• DBMS may provide protection or security measures to prevent unauthorized access
• They can provide Presentation and Visualization of data
• Backup and Restoring of the database

Interaction with Database

• Front-end applications facilitate interaction between users and the DBMS
• End-users (business users) utilize database systems to support their tasks and processes
• Indirect interaction occurs when an end-user communicates with the database through front-end applications
• Direct interaction occurs when an end-user communicates with the database directly through the DBMS

Development of Database Systems

• Requirements collection, definition, and visualization result in specifications for a database's data, capabilities, and functionalities
• This involves clearly defined and visualized collected requirements
• A conceptual database model is a visualization of requirements using a technique, such as entity-relationship (ER) modeling
• Iterative nature of the database requirements collection, definition, and visualization process
• Database modeling (logical) creates a database model that is implementable by the DBMS software
• Logical database modeling follows conceptual database modeling
• Database implementation involves using a DBMS to implement the database model as an actual database
• Most modern databases use a relational DBMS (RDBMS) software, and SQL (Structured Query Language) is used by most RDBMS packages
• Developing front-end applications involves designing applications for indirect use
• These applications are based on the database model and front-end functionalities
• Front-end applications have interfaces accessible via a navigation mechanism, such as forms and reports
• Database deployment: releasing the database system for end users
• Database use: the insertion, modification, deletion, and retrieval of data
• Database administration and maintenance include support activities for the DB end-user
• It includes dealing with technical issues such as Security, Hard-drive Space, and Backup and Recovery Procedures

People Involved with Database Systems

• Database analysts are involved in the requirements collection, definition, and visualization
• Database designers (modelers/architects) are involved in the database modeling, and must communicate with the end users
• Responsible for defining the content, structure, constraints, and functions relating to the database
• Database developers implement the database as a working model using the DBMS software
• Front-end application analysts collect and define requirements for front-end applications
• Front-end application developers create the front-end applications
• Database administrators (DBAs) handle maintenance, and administration
• Responsible for authorizing access to the DB, coordinating its use, acquiring hardware/software, controlling its use and monitoring efficiency
• Database end users use the data for queries and reports, that may or may not be updated in the database
• Use the DB to support Tasks and Processes

End users can be categorized into

• Casual: access data occasionally when needed
• Naive/Parametric: make up a large section of the end-user population, they use well-defined functions in the form of “canned transactions.” Examples include Users of Mobile Apps, Bank-tellers or Reservations Clerks
• Sophisticated: business analysts, scientists, and engineers who are familiar with the system capabilities
• Stand-alone: Maintain personal databases with ready-to-use applications or tax programs that create their own internal databases.

Operational vs. Analytical Databases

• Operational information (transactional) is collected and used in businesses, and other organizations
• Analytical information is the information collected and used in support of analytical tasks. It is based on operational (transactional) information
• Analytical Database collects and presents analytical information to support the tasks

Advantages of Using the Database Approach

• Controlling redundancy in data storage and in development and maintenance
• Restricting unauthorized access to data
• Providing Storage Structures (e.g. indexes) for efficient Query Processing
• Providing optimization of queries for efficient processing
• Providing backup and recovery services
• Providing multiple interfaces to different classes of users
• Enforcing integrity constraints on the database