7.5: Fundamental Database Concepts

Properties

A database has the following properties:

• It is a representation of some aspect of the real world or a collection of data elements (facts) representing real-world information.
• A database is logical, coherent and internally consistent.
• A database is designed, built and populated with data for a specific purpose.
• Each data item is stored in a field.
• A combination of fields makes up a table.
• Many tables are contained in a database.

For example, each field in an employee table contains data about an individual employee.  

Database features

Managing information means taking care of it so that it works for us and is useful for the tasks we perform. By using a DBMS, the information we collect and add to its database is no longer subject to accidental disorganization. It becomes more accessible and integrated with the rest of our work. Managing information using a database allows us to become strategic users of the data we have.

We often need to access and re-sort data for various uses. These may include:

• Creating mailing lists
• Writing management reports
• Generating lists of selected news stories
• Identifying various client needs

The processing power of a database allows it to manipulate the data it houses, so it can:

• Sort
• Match
• Link
• Aggregate
• Skip fields
• Calculate
• Arrange

Because of the versatility of databases, we find them powering all sorts of projects. A database can be linked to:

• A website that is capturing registered users
• A client-tracking application for social service organizations
• A medical record system for a health care facility
• Your personal address book in your email client
• A collection of word-processed documents
• A system that issues airline reservations

Database benefits

There are a number of characteristics that distinguish the database approach from the file-based system or approach.

Some of the benefits of a DB are:

• Self-describing nature of a database system: A database system is referred to as self-describing because it not only contains the database itself, but also metadata which defines and describes the data and relationships between tables in the database. This information is used by the DBMS software or database users if needed. This separation of data and information about the data makes a database system totally different from the traditional file-based system in which the data definition is part of the application programs.
• Insulation between program and data: In the file-based system, the structure of the data files is defined in the application programs so if a user wants to change the structure of a file, all the programs that access that file might need to be changed as well. On the other hand, in the database approach, the data structure is stored in the system catalog and not in the programs. Therefore, one change is all that is needed to change the structure of a file. This insulation between the programs and data is also called program-data independence.
• Support for multiple views of data: A database supports multiple views of data. A view is a subset of the database, which is defined and dedicated for particular users of the system. Multiple users in the system might have different views of the system. Each view might contain only the data of interest to a user or group of users.
• Sharing of data and multi-user system: Current database systems are designed for multiple users. That is, they allow many users to access the same database at the same time. This access is achieved through features called concurrency control strategies. These strategies ensure that the data accessed is always correct and that data integrity is maintained. The design of modern multi-user database systems is a great improvement from those in the past which restricted usage to one person at a time.
• Control of data redundancy: In the database approach, ideally, each data item is stored in only one place in the database. In some cases, data redundancy still exists to improve system performance, but such redundancy is controlled by application programming and kept to minimum by introducing as little redundancy as possible when designing the database. 
• Data sharing: The integration of all the data, for an organization, within a database system has many advantages. First, it allows for data sharing among employees and others who have access to the system. Second, it gives users the ability to generate more information from a given amount of data than would be possible without the integration.
• Enforcement of integrity constraints: Database management systems must provide the ability to define and enforce certain constraints to ensure that users enter valid information and maintain data integrity. There are many types of database constraints.

  • Data type, for example, determines the sort of data permitted in a field, for example numbers only.

  • Data uniqueness such as the primary key ensures that no duplicates are entered.

• Restriction of unauthorized access: Not all users of a database system will have the same accessing privileges. For example, one user might have read-only access (i.e., the ability to read a file but not make changes), while another might have read and write privileges, which is the ability to both read and modify a file. For this reason, a database management system should provide a security subsystem to create and control different types of user accounts and restrict unauthorized access.

• Data independence: Another advantage of a database management system is how it allows for data independence. In other words, the system data descriptions or data describing data (metadata) are separated from the application programs. This is possible because changes to the data structure are handled by the database management system and are not embedded in the program itself.

• Transaction processing: A database management system must include concurrency control subsystems. This feature ensures that data remains consistent and valid during transaction processing even if several users update the same information.

• Provision for multiple views of data: By its very nature, a DBMS permits many users to have access to its database either individually or simultaneously. It is not important for users to be aware of how and where the data they access is stored.

• Backup and recovery facilities: Backup and recovery are methods that allow you to protect your data from loss. The database system provides a separate process, from that of a network backup, for backing up and recovering data. If a hard drive fails and the database stored on the hard drive is not accessible, the only way to recover the database is from a backup. If a computer system fails in the middle of a complex update process, the recovery subsystem is responsible for making sure that the database is restored to its original state.

Data model

The most popular data model in use today is the relational data model (Oracle, MS SQL Server, IBM DB2, PostgreSQL, MySQL).

Other traditional models, such as hierarchical data models and network data models, are still used in industry mainly on mainframe platforms (hierarchical: IBM IMS, RDM; network: IDMS, Raima). 

In recent years, the newer object-oriented data models were introduced. This model is a DBMS in which information is represented in the form of objects as used in object-oriented programming (OOP). Object-oriented (OO) databases are different from relational databases, which are table-oriented. OODBMS combine database capabilities with OOP language capabilities. The OO models have not caught on as expected so are not in widespread use. Some examples of object-oriented DBMSs are O2, ObjectStore and Jasmine.

There are also some NoSQL or NoRel DBMS, as

• MongoDB, CouchDB, CouchBase are document-oriented NoSQL databases.
• Redis and Riak are key-value databases.
• Cassandra and HBase are column family stores.
• Neo4J is a graph database.

Single or multi-user

A DBMS can be classified based on the number of users it supports.

• It can be a single-user database system, which supports one user at a time,
• or a multi-user database system, which supports multiple users concurrently.

Database distribution

There are two main distribution systems for database systems and these, in turn, can be used to classify the DBMS.

• Centralized systems: the DBMS and database are stored at a single site that is used by several other systems too.
• Distributed database system: the actual database and the DBMS software are distributed from various sites that are connected by a computer network.
  • Homogeneous distributed database systems: use the same DBMS software from multiple sites. Data exchange between these various sites can be handled easily.
  • Heterogeneous distributed database systems: different sites might use different DBMS software, but there is additional common software to support data exchange between these sites.

End Users

End users are the people whose jobs require access to a database for querying, updating and generating reports.

Application user

The application user is someone who accesses an existing application program to perform daily tasks.

Application Programmers

These users implement specific application programs to access the stored data. They must be familiar with the DBMSs to accomplish their task.

Privileged/Super users

Are those who have elevated database access. This means they do not use the application program provided in the system to access the data in the database. Instead, they might define their own application or query the database directly using SQL or other commands.

Database Administrator (DBA)

A Database Administrator (DBA) may be one person or a group of persons in an organization responsible for authorizing access to the database, monitoring its use and managing all of the resources to support the use of the entire database system. The DBA creates and maintains databases that are used as part of applications or the data warehouse, and consults with systems analysts and programmers on projects that require access to or the creation of databases.

AWS. What is a Database Management System (DBMS)? Amazon. n.d. Link.

PGCC. INT1010: Concepts in Computing. Libretexts. 2021. Link.