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Databases and Database Users
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Basic Definitions
A collection of related data.
Known facts that can be recorded and have an implicit meaning.
Mini-world:
Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university.
Database Management System (DBMS):
A software package/ system to facilitate the creation and maintenance of a computerized database.
Database System:
The DBMS software together with the data itself. Sometimes, the applications are also included.

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Simplified database system environment

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Typical DBMS Functionality
Define a particular database in terms of its data types, structures, and constraints
Construct or Load the initial database contents on a secondary storage medium
Manipulating the database:
Retrieval: Querying, 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 – yet, keeping all data valid and consistent

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Additional DBMS Functionality
DBMS may additionally provide:
Protection or Security measures to prevent unauthorized access
“Active” processing to take internal actions on data
Presentation and Visualization of data
Maintenance of the database and associated programs over the lifetime of the database application
Called database, software, and system maintenance

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Example of a Database
(with a Conceptual Data Model)
Mini-world for the example:
Part of a UNIVERSITY environment.
Some mini-world entities:
SECTIONs (of COURSEs)
(academic) DEPARTMENTs
INSTRUCTORs

A conceptual data model identifies the highest-level relationships between the different entities. Features of conceptual data model include:
Includes the important entities and the relationships among them.
No attribute is specified.
No primary key is specified.
https://www.1keydata.com/datawarehousing/conceptual-data-model.html

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Example of a Database
(with a Conceptual Data Model)
Some mini-world relationships:
SECTIONs are of specific COURSEs
STUDENTs take SECTIONs
COURSEs have prerequisite COURSEs
INSTRUCTORs teach SECTIONs
COURSEs are offered by DEPARTMENTs
STUDENTs major in DEPARTMENTs

Note: The above entities and relationships are typically expressed in a conceptual data model, such as the ENTITY-RELATIONSHIP data model (see Chapters 3, 4)

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Example of a simple database

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Main Characteristics of the Database Approach
Self-describing nature of a database system:
A DBMS catalog stores the description of a particular database (e.g. data structures, types, and constraints)
The description is called meta-data*.
This allows the DBMS software to work with different database applications.
Insulation between programs and data:
Called program-data independence.
Allows changing data structures and storage organization without having to change the DBMS access programs.

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* Some newer systems such as a few NOSQL systems need no meta-data: they store the data definition within its structure making it self describing

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Example of a simplified database catalog

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Main Characteristics of the Database Approach (continued)
Data Abstraction:
A data model is used to hide storage details and present the users with a conceptual view of the database.
Programs refer to the data model constructs rather than data storage details
Support of multiple views of the data:
Each user may see a different view of the database, which describes only the data of interest to that user.

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Main Characteristics of the Database Approach (continued)
Sharing of data and multi-user transaction processing:
Allowing a set of concurrent users to retrieve from and to update the database.
Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted
Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database
OLTP (Online Transaction Processing) is a major part of database applications. This allows hundreds of concurrent transactions to execute per second.

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Database Users
Users may be divided into
Those who actually use and control the database content, and those who design, develop and maintain database applications (called “Actors on the Scene”), and
Those who design and develop the DBMS software and related tools, and the computer systems operators (called “Workers Behind the Scene”).

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Database Users – Actors on the Scene
Actors on the scene
Database administrators:
Responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software and hardware resources, controlling its use and monitoring efficiency of operations.
Database Designers:
Responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs.

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Database End Users
Actors on the scene (continued)
End-users: They use the data for queries, reports and some of them update the database content. End-users can be categorized into:
Casual: access database occasionally when needed
Naïve or Parametric: they make up a large section of the end-user population.
They use previously well-defined functions in the form of “canned transactions” against the database.
Users of Mobile Apps mostly fall in this category
Bank-tellers or reservation clerks are parametric users who do this activity for an entire shift of operations.
Social Media Users post and read information from websites

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Database End Users (continued)
Sophisticated:
These include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities.
Many use tools in the form of software packages that work closely with the stored database.
Stand-alone:
Mostly maintain personal databases using ready-to-use packaged applications.
An example is the user of a tax program that creates its own internal database.
Another example is a user that maintains a database of personal photos and videos.

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Database Users – Actors on the Scene (continued)
System Analysts and Application Developers

This category currently accounts for a very large proportion of the IT work force.
System Analysts: They understand the user requirements of naïve and sophisticated users and design applications including canned transactions to meet those requirements.
Application Programmers: Implement the specifications developed by analysts and test and debug them before deployment.
Business Analysts: There is an increasing need for such people who can analyze vast amounts of business data and real-time data (“Big Data”) for better decision making related to planning, advertising, marketing etc.

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Database Users – Actors behind the Scene
System Designers and Implementors: Design and implement DBMS packages in the form of modules and interfaces and test and debug them. The DBMS must interface with applications, language compilers, operating system components, etc.
Tool Developers: Design and implement software systems called tools for modeling and designing databases, performance monitoring, prototyping, test data generation, user interface creation, simulation etc. that facilitate building of applications and allow using database effectively.
Operators and Maintenance Personnel: They manage the actual running and maintenance of the database system hardware and software environment.

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Advantages of Using the Database Approach
Controlling redundancy in data storage and in development and maintenance efforts.
Sharing of data among multiple users.
Restricting unauthorized access to data. Only the DBA staff uses privileged commands and facilities.
Providing persistent storage for program Objects
E.g., Object-oriented DBMSs make program objects persistent– see Chapter 12.
Providing Storage Structures (e.g. indexes) for efficient Query Processing – see Chapter 17.

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Advantages of Using the Database Approach (continued)
Providing optimization of queries for efficient processing.
Providing backup and recovery services.
Providing multiple interfaces to different classes of users.
Representing complex relationships among data.
Enforcing integrity constraints on the database.
Drawing inferences and actions from the stored data using deductive and active rules and triggers.

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