Oodbms And Ordbms.docx

OBJECT ORIENTED DATABASE When the database techniques are combined with object oriented concepts, the result is an object oriented management system (ODBMS). Today’s trend in programming languages is to utilize objects, thereby making OODBMS is ideal for Object Oriented programmers because they can develop the product, store them as objects, and can replicate or modify existing objects to make new objects within the OODBMS. Object databases based on persistent programming acquired a niche in application areas such as engineering and spatial databases, telecommunications, and scientific areas such as high energy physics and molecular biology. List of Object Oriented Database Standards Some of the Object oriented DBMS standards are: 1. 2. 3. 4. 5.

Object data management group Object database standard ODM 6.2.0 Object query language Object query language support of SQL 92 Object Oriented Data Model(OODM)

Object oriented data models are a logical data models that capture the semantics of objects supported on object oriented programming. OODMs implement conceptual models directly and can represent complexities that are beyond the capabilities of relational systems. OODBs have adopted many of the concepts that were developed originally for object oriented programming language. An object oriented database is a collection of objects defined by an object oriented data model. An object oriented database can extend the existence of objects so that they are stored permanently. Therefore, the objects persist beyond program termination and can be retrieved later and shared by other programs.

Characteristics of Object oriented database The characteristics of object oriented database are listed below: 1. It keeps up a direct relation between real world and database objects as if objects do not lose their integrity and identity. 2. OODBs provide system generated object identifier for each object so that an object can easily be identified and operated upon. 3. OODBs are extensible, which identifies new data types and the operations to be performed on them. 4. Provides encapsulation, feature which, the data representation and the methods implementation are hidden from external entities.

5. Also provides inheritance properties in which an object inherits the properties of other objects. Object, Attributes and Identity 1. Attributes : The attributes are the characteristics used to describe objects. Attributes are also known as instance variables. When attributes are assigned values at a given time, it is assumed that the object is in a given state at that time. 2. Object : An object is an abstract representation of the real world entity which has a unique identity, embedded properties, and the ability to interact with other objects and itself. 3. Identity : The identity is an external identifier- the object ID- maintained for each object. The Object ID is assigned by the system when the object is created, and cannot be changed. It is unlike the relational database, for example, where a data value stored within the object is used to identify the object. Object oriented methodologies There are certain object oriented methodologies are use in OODB. These are: 1. Class: A class is assumed as a group of objects with the same or similar attributes and behavior. 2. Encapsulation: It is the property that the attributes and methods of an object are hidden from outside world. A published interface is used to access an object’s methods. 3. Inheritance: It is the property which, when classes are arranged in a hierarchy, each class assumes the attributes and methods of its ancestors. For example, class students are the ancestor of undergraduate students and post graduate students. 4. Polymorphism : It allows several objects to represent to the same message in different ways. In the object oriented database model, complex objects are modeled more naturally and easily. Benefit of object orientation in programming language The benefits of object orientation in programming language are: 1. 2. 3. 4. 5.

Minimizes number of lines of code Reduces development time Increases the reusability of codes Makes code maintenance easier Increased productivity of programmers

Merits of Object oriented database OODBs provide the following merits:

1. OODBs allow for the storage of complex data structures that cannot be easily stored using conventional database terminology. 2. OODBs support all the persistence required for object oriented applications. 3. OODBs contain active object servers which support both distribution of data and distribution of work. Advantages of Object oriented data model over Relational model When compared with the relational model, the object oriented data model has the following advantages: 1. Reusability: generic objects can be defined and then reused in numerous application. 2. Complex data types: Can manage complex data such as document, graphics, images, voice messages, etc. 3. Distributed databases: Due to mode of communication between objects, OODBMS can support distribution of data across networks more easily. Object oriented model vs Entity Relationship model 1. An entity is simply a collection of variables or data items. 2. When an application is running, the ER Model will tells how the application’s data will be persisted but the Object Oriented Model will decide that how that data will be stored in the memory. OODB vs RDBMS

OBJECT-RELATIONAL DBMS ORDBMSs synthesize the features of RDBMSs with the best ideas of OODBMSs. Although ORDBMSs reuse the relational model as SQL interprets it, the OR data model is opened up in novel ways. New data types and functions can be implemented using generalpurpose languages such as C and Java. In other words, ORDBMSs allow developers to embed new classes of data objects into the relational data model abstraction. ORDBMS schemas have additional features not present in RDBMS schema. Several OO structural features such as inheritance and polymorphism are part of the OR data model. ORDBMSs adopt the RDBMS query-centric approach to data management. All data access in an ORDBMS is handled with declarative SQL statements. There is no procedural, or object-at-atime, navigational interface. ORDBMSs persist with the idea of a data language that is fundamentally declarative, and therefore mismatched with procedural OO host languages. This significantly affects the internal design of the ORDBMS engine, and it has profound implications for the interfaces developers use to access the database.

From a systems architecture point of view, ORDBMSs are implemented as a central server program rather than as a distributed data architectures typical in OODBMS products. However, ORDBMSs extend the functionality of DBMS products significantly, and an information system using an ORDBMS can be deployed over multiple machines. Comparing the RDBMS with the ORDBMS When we compare the RDBMS with the ORDBMS the following aspects can be noted: • An ORDBMS is a relational DBMS with SQL3 extensions. • SQL3 extensions include: row types, user-defined types and user-defined routines, polymorphism, inheritance, reference types and object identity, collection types (ARRAYs), new language constructs that make SQL computationally complete, triggers and support for language objects – Binary Large Objects (BLOBs) and Character Large Objects (CLOBs) – and recursion. • A RDBMS is characterized by simplicity and increased stability as compared to an ORDBMS, and this fact confers it the quality of being easily used. • Traditional RDBMS use B – tree indexes to speed access to scalar data. With the ability to define complex data types in an ORDBMS, specialized index structures are required for efficient to data. Some ORDBMSs are beginning to support additional index types, such as generic Btrees, R-trees (region trees) for fast access to two – and three dimensional data, and the ability to index on the output of a function. • A mechanism to plug in any user – defined index structure provides the highest level of flexibility. • Both DBMSs are characterized by simplicity of development owing to the fact that it provides independence of data from applications good for simple relationships. • For RDBMS there is SQL2 standard (ANSI X3H2) and for ORDBMS there is SQL3 standard. • RDBMS is a mature software product while ORDBMS is an immature product (extensions are new, thy are still being defined and are relatively unproven. • As far as the support for object – oriented programming is concerned, with the RDBMS, programmers spend 25% of coding time mapping the program object to the database, and with the ORDBMS, the support for object-oriented programming is limited mostly to new data types. Comparing OODBMS with ORDBMS When we compared OODBMS with ORDBMS some conclusions can be drawn: • OODBMSs and ORDBMSs both support user-defined ADTs, structured types, object identity and reference types, and inheritance.

• They both support a query language for manipulating collection types; • ORDBMSs support an extended form of SQL, and OODBMSs support ODL/OQL; • ORDBMSs consciously try to add OODBMS features to an RDBMS, and OODBMS in their turn have developed query languages based on relational query languages; • Both OODBMSs and ORDBMSs provide DBMS functionality such as concurrency control and recovery; • OODBMSs try to add DBMS functionality to a programming language, whereas ORDBMSs try to add richer data types to a relational DBMS.