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.
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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.
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.
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.
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.
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.
Object Relational Database Management System (ORDBMS) is a DBMS or Database Management System akin to a relational database, but with an object oriented database model that allows custom web development professionals to combine the database with custom data types. It bridges the gap between relational databases and Object-Oriented Database Management System (OODBMS).
Traditional RDBMS (Relational Database Management System) focused on the efficient management from a limited set of data-types. Object relational DBMS allows web sites development experts to combine their own data types and methods.
The limitations of RDBMS have led to the introduction of object-relational database management systems ORDBMS systems occurred in the early 1990s out of research. One of the most notable research projects, the Postgres introduced two products Illustra and Postgre SQL. The mid-1990s saw many commercial products appearing. These included Omniscience, UniSQL and Illustra 2.
Objectives of Object Relational Databases:
To bridge the gap between object-relational mapping and conceptual data modeling techniques.
To bridge the gap between object oriented modeling techniques (used in programming languages like C++, C# and Java) and relational databases.
Advantages of ORDBMS:
Object Relational Database Management Systems ensures large storage capacity, which is an important part in web based development
The access speed is fairly quick.
ORDBMSs have massive scalability.
ORDBMSs boast excellent manipulation power of object databases.
Supports object functionality by adding separate APIs and server subsystems
Redesigns the database engine completely
Supports rich data types by adding a new object-oriented layer.
Apart from these benefits, an object relational database management system has some drawbacks. One of the major disadvantages is its incapability for high-speed internet applications. However, ORDBMSs are designed to manage large amounts of information, an important aspect in the development of website. The IDC opines that the ORDBMS market has the potential to surpass the size of ODBMS in the next couple of years in web based development.
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An object relational database is also called an object relational database management system (ORDBMS). This system simply puts an object oriented front end on a relational database (RDBMS). When applications interface to this type of database, it will normally interface as though the data is stored as objects. However the system will convert the object information into data tables with rows and colums and handle the data the same as a relational database. Likewise, when the data is retrieved, it must be reassembled from simple data into complex objects.
Because the ORDBMS converts data between an object oriented format and RDBMS format, speed performance of the database is degraded substantially. This is due to the additional conversion work the database must do.
The main benefit to this type of database lies in the fact that the software to convert the object data between a RDBMS format and object database format is provided. Therefore it is not necessary for programmers to write code to convert between the two formats and database access is easy from an object oriented computer language.
To define Object-Relational Database Management System (ORDBMS) it is enough to take simple equation: ORDBMS = ODBMS + RDBMS = (O + R) * DB * MS. On a logical level, an ORDBMS is the MS process methods applied for DB data structure, which is complied with O object and R relational concepts.
The R relational concept in the context of DBMS is based on the relations in the form of two-dimensional tables of rows and columns. Transformation of queries into relational algebra is the main confirmation that affiliates a database with the relational model. It is prejudice to think that SQL2 language is a single and necessary criterion of RDBMS just as to think that Java is a single language of OO programming. Noteworthy feature of RDBMS is the possibility to process a large mass of the uniform n-element tuples (rows or records) quickly.
All necessary for object representation is available in the object DBMS (ODBMS). Often the ODBMS is equated to the OODBMS, namely DBMS integrated with an Object-Oriented (OO) programming language like C++ and Java. The characteristic properties of ODBMS are 1) complex data, 2) type inheritance, and 3) object behavior. These features will be considered below regarding the ORDBMS.
Complex data creation in most SQL ORDBMSs is based on preliminary schema definition via the user-defined type (UDT). The table remains a most clear form for representation of complex data in any ORDBMS.
Computers in Engineering
The “name” attribute (or field or column) consists of the “first” and “last” attributes. The value of the “course” attribute is a set of “Economy” and “Planning” elements. Such structure is able, for example, for the Informix SQL (http://www-3.ibm.com/software/data/informix/pubs/library/index.html).
CREATE ROW TYPE Student (
name ROW (first VARCHAR(12), last VARCHAR(20)),
course SET (VARCHAR(128) NOT NULL)
CREATE TABLE students OF TYPE Student;
INSERT INTO students
INSERT INTO students
SET(‘Computers in Engineering’)
Other SQL ORDBMS suggests other composite type constructors, for example VARRAY or ARRAY instead of the SET, and OBJECT instead of the ROW. Constructors of the simple built-in types, with limitations like CHAR(5), came from SQL2.
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An object-oriented database management system (OODBMS), sometimes shortened to ODBMS for object database management system), is a database management system (DBMS) that supports the modelling and creation of data as objects. This includes some kind of support for classes of objects and the inheritance of class properties and methods by subclasses and their objects. There is currently no widely agreed-upon standard for what constitutes an OODBMS, and OODBMS products are considered to be still in their infancy. In the meantime, the object-relational database management system (ORDBMS), the idea that object-oriented database concepts can be superimposed on relational databases, is more commonly encountered in available products. An object-oriented database interface standard is being developed by an industry group, the Object Data Management Group (ODMG). The Object Management Group (OMG) has already standardized an object-oriented data brokering interface between systems in a network.
In their influential paper, The Object-Oriented Database Manifesto, Malcolm Atkinson and others define an OODBMS as follows:
An object-oriented database system must satisfy two criteria: it should be a DBMS, and it should be an object-oriented system, i.e., to the extent possible, it should be consistent with the current crop of object-oriented programming languages. The first criterion translates into five features: persistence, secondary storage management, concurrency, recovery and an ad hoc query facility. The second one translates into eight features: complex objects, object identity, encapsulation, types or classes, inheritance, overriding combined with late binding, extensibility and computational completeness.
OODBMS (OBJECT DATABASE) ADVANTAGES
Using an OODBMS / ODBMS (object database management system, object-oriented data management system) for data storage brings powerful advantages to applications that use complex object models, have high concurrency requirements, and large data sets.
It is difficult, time consuming, expensive in development, and expensive at run time, to map the objects into a relational database and performance can suffer. Versant’sobject database solutions (ODBMS) are designed to handle the navigational access, seamless data distribution, and scalability often required by these applications:
Versant Object Database OODBMS (Java, C++)
FastObjects .NET OODBMS (.NET)
Why Versant’s OODBMS solutions instead of traditional RDBMS?
Where data handling requirements are simple and suitable to rigid row and column structures an RDBMS might be an appropriate solutiuon. However,for many applications, today’s most challenging aspect is controlling the inherent complexity of the subject matter itself – the complexity must be tamed. And tamed in a way that enables continual evolution of the application as the environment and needs change. For these applications, an OODBMS is the best answer:
COMPLEX (INTER-) RELATIONSHIPS
If there are a lot of many-to-many relationships, tree structures or network (graph) structures then Versant’s OODBMS solutions will handle those relationships much faster than a relational database.
For many applications, the most challenging aspect is controlling the inherent complexity of the subject matter itself – the complexity must be tamed. For these applications, a Versant OODBMS is the best answer. Architectures that mix technical needs such as persistence (and SQL) with the domain model are an invitation to disaster. Versant’s OODBMS solutions let you develop using objects that need only contain the domain behaviour, freeing you from persistence concerns.
NO MAPPING LAYER
It is difficult, time consuming, expensive in development, and expensive at run time, to map the objects into a relational database and performance can suffer. Versant’sOODBMS solutions store objects as objects – yes, it’s as easy as 1, 2, 3. Versant’s object database solutions are designed to store many-to-many, tree and network relationships as named bi-directional associations without having the need for JOIN tables. Hence, Versant’s object database solutions save programming time, and objects can be stored and retrieved faster. Modern O/R mapping tools may simplify many mapping problems, however they don’t provide seamless data distribution or the performance of Versant’s OODBMS solutions.
FAST AND EASY DEVELOPEMENT, ABILITY TO COPE WITH CONTINOUS EVOLUTION
The complexity of telecommunications infrastructure, transportation networks, simulations, financial instruments and other domains must be tamed. And tamed in a way that enables continual evolution of the application as the environment and needs change. Architectures that mix technical needs such as persistence (and SQL) with the domain model are an invitation to disaster. Versant’s OODBMSsolutions let you develop using objects that need only contain the domain behaviour, freeing you from persistence concerns.
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