Introduction to RDBMS, OODBMS and ORDBMS

Thanks to the Internet, the legal need to keep track of lots of business information, new marketing methods, and the explosion of data-intensive scientific progress, databases are being used more than ever before for storing and accessing information. There are currently three different models in use for database management systems: relational, object-oriented, and object-relational. This article introduces all three, and discusses their relative strengths and weaknesses.


Relational Database Management System

Edgar F. Codd at IBM invented the relational database in 1970. Referred to as RDBMS, the relational model extended two previous database systems, the hierarchical and the network models. After Codd’s development, “prototype RDBMS were developed at IBM and UC-Berkeley, and several vendors were offering relational database products shortly thereafter.”

The relational model is based on the structure of a database. A database is simply a collection of one or more relations or tables with columns and rows. The use of set theory allows for data to be structured in a series of tables that has both columns and rows. Each column corresponds to an attribute of that relation, while each row corresponds to a record that contains data values for an entity.

The main elements of RDBMS are based on Ted Codd’s 13 rules for a relational system, the concept of relational integrity, and normalization. The three fundamentals of a relational database are that all information must be held in the form of a table, where all data are described using data values. The second fundamental is that each value found in the table columns does not repeat. The final fundamental is the use of Standard Query Language (SQL).

Benefits of RDBMS are that the system is simple, flexible, and productive. Because the tables are simple, data is easier to understand and communicate with others. RDBMS are flexible because users do not have to use predefined keys to input information. Also, RDBMS are more productive because SQL is easier to learn. This allows users to spend more time inputting instead of learning. More importantly, RDBMS’s biggest advantage is the ease with which users can create and access data and extend it if needed. After the original database is created, new data categories can be added without the existing application being changed.

There are limitations to the relational database management system. First, relational databases do not have enough storage area to handle data such as images, digital and audio/video. The system was originally created to handle the integration of media, traditional fielded data, and templates. Another limitation of the relational database is its inadequacy to operate with languages outside of SQL. After its original development, languages such as C++ and JavaScript were formed. However, relational databases do not work efficiently with these languages. A third limitation is the requirement that information must be in tables where relationships between entities are defined by values.

Today, the relational model is the dominant data model as well as the foundation for the leading DBMS products, which include IBM’s DB2 family, Informix, Oracle, Sybase, Microsoft’s Access and SQLServer, as well as FoxBase and Paradox. RDBMS represent close to a multibillion-dollar industry alone.

{mospagebreak title=Object-Oriented Database Management System}

To combat the limitations of RDBMS and meet the challenge of the increasing rise of the Internet and the Web, programmers developed object-oriented databases in the 1980s. The main objective of Object-Oriented Database Management Systems, commonly known as OODBMS, is to provide consistent, data independent, secure, controlled and extensible data management services to support the object-oriented model. They were created to handle big and complex data that relational databases could not.

There are important characteristics involved with object-oriented databases. The most important characteristic is the joining of object-oriented programming with database technology, which provides an integrated application development system. Object-oriented programming results in 4 main characteristics: inheritances, data encapsulation, object identity, and polymorphism. Inheritance allows one to develop solutions to complex problems incrementally by defining new objects in terms of previously defined objects.

Data encapsulation or simply encapsulation allows the hiding of the internal state of the objects. Encapsulated objects are those objects that can only be assessed by their methods instead of their internal states. There are three types of encapsulated objects users and developers should recognize. The first is full encapsulation, in which all the operations on objects are done through message sending and method execution. The second is write encapsulation, which is where the internal state of the object is visible only for reading operations. The third is partial encapsulation, which involves allowing direct access for reading and writing for only a part of the internal state.

Object identity allows objects of the database to be independent of each other. Polymorphism and dynamic binding allow one to define operations for one object and then to share the specification of the operation with other objects. This allows users and/or programmers to compose objects to provide solutions without having to write code that is specific to each object.

The language important to OODBMS is data definition and manipulation language (DDML). The use of this language allows persistent data to be created, updated, deleted, or retrieved. An OODBMS needs a computational versus a relational language because it can be used to avoid impedance mismatch. DDML allows users to define a database, including creating, altering, and dropping tables and establishing constraints. DDMLs are used to maintain and query a database, including updating, inserting, modifying, and querying data.

The OODBMS has many advantages and benefits. First, object-oriented is a more natural way of thinking. Second, the defined operations of these types of systems are not dependent on the particular database application running at a given moment. Third, the data types of object-oriented databases can be extended to support complex data such as images, digital and audio/video, along with other multi-media operations. Different benefits of OODBMS are its reusability, stability, and reliability. Another benefit of OODBMS is that relationships are represented explicitly, often supporting both navigational and associative access to information. This translates to improvement in data access performance versus the relational model.

Another important benefit is that users are allowed to define their own methods of access to data and how it will be represented or manipulated. The most significant benefit of the OODBMS is that these databases have extended into areas not known by the RDBMS. Medicine, multimedia, and high-energy physics are just a few of the new industries relying on object-oriented databases.

As with the relational database method, object-oriented databases also has disadvantages or limitations. One disadvantage of OODBMS is that it lacks a common data model. There is also no current standard, since it is still considered to be in the development stages.

{mospagebreak title=Characteristics of Object-Oriented Databases in Depth}

Object-oriented database technology is a marriage of object-oriented programming and database technologies. Figure 1 illustrates how these programming and database concepts have come together to provide what we now call object-oriented databases.

 

Introduction to RDBMS OODBMS and ORDBMS

Perhaps the most significant characteristic of object-oriented database technology is that it combines object-oriented programming with database technology to provide an integrated application development system. There are many advantages to including the definition of operations with the definition of data. First, the defined operations apply ubiquitously and are not dependent on the particular database application running at the moment. Second, the data types can be extended to support complex data such as multi-media by defining new object classes that have operations to support the new kinds of information.

Other strengths of object-oriented modeling are well known. For example, inheritance allows one to develop solutions to complex problems incrementally by defining new objects in terms of previously defined objects. Polymorphism and dynamic binding allow one to define operations for one object and then to share the specification of the operation with other objects. These objects can further extend this operation to provide behaviors that are unique to those objects. Dynamic binding determines at runtime which of these operations is actually executed, depending on the class of the object requested to perform the operation. Polymorphism and dynamic binding are powerful object-oriented features that allow one to compose objects to provide solutions without having to write code that is specific to each object. All of these capabilities come together synergistically to provide significant productivity advantages to database application developers.

A significant difference between object-oriented databases and relational databases is that object-oriented databases represent relationships explicitly, supporting both navigational and associative access to information. As the complexity of interrelationships between information within the database increases, so do the advantages of representing relationships explicitly. Another benefit of using explicit relationships is the improvement in data access performance over relational value-based relationships.

A unique characteristic of objects is that they have an identity that is independent of the state of the object. For example, if one has a car object and we remodel the car and change its appearance, the engine, the transmission, and the tires so that it looks entirely different, it would still be recognized as the same object we had originally. Within an object-oriented database, one can always ask the question, “is this the same object I had previously?”, assuming one remembers the object’s identity. Object-identity allows objects to be related as well as shared within a distributed computing network.

All of these advantages point to the application of object-oriented databases to information management problems that are characterized by the need to manage:

  • a large number of different data types,

  • a large number of relationships between the objects, and

  • objects with complex behaviors.

Application areas where this kind of complexity exists includes engineering, manufacturing, simulations, office automation and large information systems.

{mospagebreak title=Object-Relational Database}

Object-Relational database (ORDBMS) is the third type of database common today. ORDBMS are systems that “attempt to extend relational database systems with the functionality necessary to support a broader class of applications and, in many ways, provide a bridge between the relational and object-oriented paradigms.”

ORDBMS was created to handle new types of data such as audio, video, and image files that relational databases were not equipped to handle. In addition, its development was the result of increased usage of object-oriented programming languages, and a large mismatch between these and the DBMS software.

One advantage of ORDBMS is that it allows organizations to continue using their existing systems, without having to make major changes. A second advantage is that it allows users and programmers to start using object-oriented systems in parallel.

There are challenges in implementing an ORDBMS. The first is storage and access methods. The second is query processing, and the third is query optimization.

Since the development of RDBMS, OODBMS, and ORDBMS, many vendors have extended their systems with the ability to store new data types such as images and texts, and with the ability to ask more complex queries.

One rising technique is enterprise resource planning and management resource planning, which add another layer of application-oriented features on top of a DBMS. Included applications come from Baan, Oracle, SAP, and Siebel. These programs each identify a set of common tasks encountered by a large number of organizations and provide a general application layer to carry out these tasks.

More importantly, DBMS have advanced into the Internet and Web Age. Stored data is widely being accessed through a Web browser. Today, queries are being generated through Web-accessible forms and answers are being formatted using a mark-up language such as HTML. In addition, many vendors and distributors are adding features to their DBMS aimed at making it better equipped for Internet usage.

In summary, relational and object-oriented database systems each have certain strengths as well as certain weaknesses. In general, the weakness of one type of system tends to be strength of the other.

8 thoughts on “Introduction to RDBMS, OODBMS and ORDBMS

  1. pretty good article..introduces us to the basics of it.i did not know much abt it before i read it.i now can go into details of it.oh well..i m a student.so it was helpful to start off
    thanks!

  2. for starter its a nice note, i have gather very nice information a basic concept regarding these concepts. Thank’s for posting the material.

  3. good topic for all students who are taking up computer courses.we can get lots of information about this topic..

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