Object oriented modeling
- 1. Prof. Neeraj Bhargava Pooja Dixit Department of Computer Science School of Engineering & System Science MDS, University Ajmer, Rajasthan, India 1
- 2. An object database is a database management system in which information is represented in the form of objects as used in object-oriented programming. Object databases are different from relational databases which are table-oriented. Object- relational databases are a hybrid of both approaches. OODBMSs allow object-oriented programmers to develop the product, store them as objects, and replicate or modify existing objects to make new objects within the OODBMS. Because the database is integrated with the programming language, the programmer can maintain consistency within one environment, in that both the OODBMS and the programming language will use the same model of representation. Object-oriented modeling (OOM) is the construction of objects using a collection of objects that contain stored values of the instance variables found within an object. Unlike models that are record-oriented, object-oriented values are solely objects. 2
- 3. An object-oriented database is a database that subscribes to a model with information represented by objects. Object-oriented databases are a niche offering in the relational database management system (RDBMS) field and are not as successful or well- known as mainstream database engines. As the name implies, the main feature of object-oriented databases is allowing the definition of objects, which are different from normal database objects. Objects, in an object-oriented database, reference the ability to develop a product, then define and name it. The object can then be referenced, or called later, as a unit without having to go into its complexities. This is very similar to objects used in object- oriented programming. A real-life parallel to objects is a car engine. It is composed of several parts: the main cylinder block, the exhaust system, intake manifold and so on. Each of these is a standalone component; but when machined and bolted into one object, they are now collectively referred to as an engine. Similarly, when programming one can define several components, such as a vertical line intersecting a perpendicular horizontal line while both lines have a graded measurement. This object can then be collectively labeled a graph. 3
- 4. OODB = Object Orientation + Database Capabilities FEATURES TO BE CONSIDERED: Persistence support of transactions simple querying of bulk data concurrency control resilience and recovery Security Versioning integrity performance issues • DATA MODELS TO BE CONSIDERED: Complex object model Semantic data model such as Extended ER (EER) model OPM model 4
- 5. The Object-Oriented Data Model A data model is a logic organization of the real world objects (entities), constraints on them, and the relationships among objects. A DB language is a concrete syntax for a data model. A DB system implements a data model. A core object-oriented data model consists of the following basic object-oriented concepts: (1) object and object identifier: Any real world entity is uniformly modeled as an object (associated with a unique id: used to pinpoint an object to retrieve). (2) attributes and methods: every object has a state (the set of values for the attributes of the object) and a behavior (the set of methods - program code - which operate on the state of the object). The state and behavior encapsulated in an object are accessed or invoked from outside the object only through explicit message passing. (3) class: a means of grouping all the objects which share the same set of attributes and methods. An object must belong to only one class as an instance of that class (instance-of relationship). A class is similar to an abstract data type. A class may also be primitive (no attributes), e.g., integer, string, Boolean. (4) Class hierarchy and inheritance: derive a new class (subclass) from an existing class (superclass). The subclass inherits all the attributes and methods of the existing class and may have additional attributes and methods. single inheritance (class hierarchy) vs. multiple inheritance (class lattice). 5