Object-oriented databases are a type of database management system. Different database management systems provide additional functionalities. Object-oriented databases add the database functionality to object programming languages, creating more manageable code bases.
This article gives an in-depth overview of object-oriented databases with examples.
Object Database Definition
An object database is managed by an object-oriented database management system (OODBMS). The database combines object-oriented programming concepts with relational database principles.
- Objects are the basic building block and an instance of a class, where the type is either built-in or user-defined.
- Classes provide a schema or blueprint for objects, defining the behavior.
- Methods determine the behavior of a class.
- Pointers help access elements of an object database and establish relations between objects.
The main characteristic of objects in OODBMS is the possibility of user-constructed types. An object created in a project or application saves into a database as is.
Object-oriented databases directly deal with data as complete objects. All the information comes in one instantly available object package instead of multiple tables.
In contrast, the basic building blocks of relational databases, such as PostgreSQL or MySQL, are tables with actions based on logical connections between the table data.
These characteristics make object databases suitable for projects with complex data which require an object-oriented approach to programming. An object-oriented management system provides supported functionality catered to object-oriented programming where complex objects are central. This approach unifies attributes and behaviors of data into one entity.
Object-Oriented Programming Concepts
Object-oriented databases closely relate to object-oriented programming concepts. The four main ideas of object-oriented programming are:
These four attributes describe the critical characteristics of object-oriented management systems.
Polymorphism is the capability of an object to take multiple forms. This ability allows the same program code to work with different data types. Both a car and a bike are able to break, but the mechanism is different. In this example, the action break is a polymorphism. The defined action is polymorphic — the result changes depending on which vehicle performs.
Inheritance creates a hierarchical relationship between related classes while making parts of code reusable. Defining new types inherits all the existing class fields and methods plus further extends them. The existing class is the parent class, while the child class extends the parent.
For example, a parent class called Vehicle will have child classes Car and Bike. Both child classes inherit information from the parent class and extend the parent class with new information depending on the vehicle type.
Encapsulation is the ability to group data and mechanisms into a single object to provide access protection. Through this process, pieces of information and details of how an object works are hidden, resulting in data and function security. Classes interact with each other through methods without the need to know how particular methods work.
As an example, a car has descriptive characteristics and actions. You can change the color of a car, yet the model or make are examples of properties that cannot change. A class encapsulates all the car information into one entity, where some elements are modifiable while some are not.
Abstraction is the procedure of representing only the essential data features for the needed functionality. The process selects vital information while unnecessary information stays hidden. Abstraction helps reduce the complexity of modeled data and allows reusability.
For example, there are different ways for a computer to connect to the network. A web browser needs an internet connection. However, the connection type is irrelevant. An established connection to the internet represents an abstraction, whereas the various types of connections represent different implementations of the abstraction.
Object-Oriented Database Examples
There are different kinds of implementations of object databases. Most contain the following features:
|Query Language||Language to find objects and retrieve data from the database.|
|Transparent Persistence||Ability to use an object-oriented programming language for data manipulation.|
|ACID Transactions||ACID transactions guarantee all transactions are complete without conflicting changes.|
|Database Caching||Creates a partial replica of the database. Allows access to a database from program memory instead of a disk.|
|Recovery||Disaster recovery in case of application or system failure.|
GemStone/S is an object database system based on Smalltalk – an object-oriented programming language influenced by Java. Developers who write applications in Smalltalk adapt easily to this database. GemStone/S integrates seamlessly with existing Smalltalk applications, improving speed and productivity.
Gemstone/S is best for high-availability projects. There are multiple options for licensing depending on the project size. The database server is available for various platforms, including Linux, Windows, macOS, Solaris, AIX, as well as Raspberry Pi.
ObjectDB is a NoSQL object database for the Java programming language. Compared to other NoSQL databases, ObjectDB is ACID compliant. ObjectDB does not provide an API and requires using one of the two built-in Java database APIs:
- JPA with JPA Query Language (JPQL) based on Java syntax.
- JDO with JDO Query Language (JDQL) based on SQL syntax.
ObjectDB includes all basic data types in Java, user-defined classes, and standard Java collections. Every object has a unique ID. The number of elements is limited only by the maximum database size (128 TB). ObjectDB is available cross-platform and the benchmark performance is exceptional.
ObjectDatabase++ is a real-time embeddable object database designed for server-side applications. The required external maintenance is minimal.
- Multi-process with multi-threaded server applications.
- Full transaction control.
- Real-time recovery.
- C++ related languages, VB.NET as well as C#.
The object database is C++ based. One of the main features is advanced auto-recovery from system crashes without compromising the database integrity.
Objectivity/DB utilizes the power of objects and satisfies the complex requirements within Big Data. The object database is flexible by supporting multiple languages:
The schema changes happen dynamically without the need for downtime, allowing real-time queries against any data type. Objectivity/DB is available for multiple platforms, including macOS, Linux, Windows, or Unix.
ObjectStore integrates with C++ or Java and provides memory persistency to improve the performance of application logic. The object database is ACID-compliant. The responsiveness allows developers to build distributed applications cross-platform, whether on-premises or in the cloud.
The main feature is cloud scalability, which allows database access from anywhere. ObjectStore simplifies the data creation and exchange process seamlessly.
Versant provides primary transparent object persistence from C++, Java, and .NET. However, there is also support for Smalltalk and Python. Versant supports different APIs depending on the language used. Standard SQL queries are also available, making Versant a NoSQL database.
The object database is a multi-user client-server database. Versant performs best when used for online transaction systems with large amounts of data and concurrent users.
Object-Oriented Database Advantages and Disadvantages
Every database modeling technique has advantages and disadvantages. Before opting in for object-oriented databases, you must know the available languages in addition to the application intent.
The main advantages are:
- Complex data and a wider variety of data types compared to MySQL data types.
- Easy to save and retrieve data quickly.
- Seamless integration with object-oriented programming languages.
- Easier to model the advanced real world problems.
- Extensible with custom data types.
Some disadvantages include:
- Not as widely adopted as relational databases.
- No universal data model. Lacks theoretical foundations and standards.
- Does not support views.
- High complexity causes performance issues.
- An adequate security mechanism and access rights to objects do not exist.
Object databases provide a modern approach to database modeling, mirroring the used in object-oriented programming. Learn more about database technologies in our blog article What is database as a service (DBaaS).