Specialty Databases

Several application areas for database systems are limited by the restrictions of the data model. As a result, researchers have developed several datamodels deal with these application domains, including object-based data models and
semistructured data models.

1. Object-Based Data Models

Object-oriented programming has become the dominant software-development. This led to the development of an object-oriented data model that be seen as extending the E-R model with notions of encapsulation, methods), and object identity. Inheritance, object identity, and encapsulation hiding), with methods to provide an interface to objects, are among key concepts of object-oriented programming that have found applications in modeling. The object-oriented data model also supports a rich type system, structured and collection types. In the 1980s, several database systems on the object-oriented data model were developed.
The major database vendors presently support the object-relational data, a data model that combines features of the object-oriented datamodel and data model. It extends the traditional relational model with a variety features such as structured and collection types, as well as object orientation.

2. Semistructured Data Models

Semistructured data models permit the specification of data where individual items of the same type may have different sets of attributes. This is in contrast the data models mentioned earlier, where every data item of a particular must have the same set of attributes.
The XML language was initially designed as a way of adding markup information text documents, but has become important because of its applications in exchange. XML provides a way to represent data that have nested structure, furthermore allows a great deal of flexibility in structuring of data, which is for certain kinds of nontraditional data. 

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