Database and Expert System Technology - Information Systems Reengineering, Integration and Normalization - page 57

class. A class consists of a class name, attributes, and methods, and can be defined
as follows:

Class <class-name>
Attributes
[inherit<class-name>]
<attribute-name>: [set] <primitive data type>/<class>
Method

[operations]

A class must have a unique name and can inherit from any other class that is not a
descendant of itself. The attribute describes the properties of a class. Its data type
can be a primitive one such as integer, numeric, and character. It can be another
class. If it is another class, it is called a complex object, which means a class is
within another class, or a nested class. If an object associates many other objects,
then we must use Set in describing the associated attributes. This is similar to 1:m
cardinality in the ER model and in a relational model.
The inherit statement is to indicate that the subclass inherits attributes and meth-
ods from its superclass. The class with the inherit statement is the subclass. The
target class after the inherit key word is the superclass. The methods are the defined/
stored operation(s) of a class.
The object-oriented DDL of UniSQL consists of Create class statement, as follows:
Create—Use a create statement to define a class. For example:

Create class Department Create class Instructor
(Dept#: integer, (Inst-name: char(30),
Dept-name: char(30), Inst-addr: char(50),
Hire: set-of Instructors) Hired-by: Department)
Procedure Procedure
Display Department. Display Instructor.

2.5 Extensible Markup Language (XML)

An XML is defined as EXtensible Markup Language (XML). Its development can
be traced up to World Wide Web Consortium (W3C 2004 ) recommendation Version
1.0 as of 10/02/1998. It describes data, rather than instructing a system on how to
process it, and provides powerful capabilities for data integration and data-driven
styling, introduces new processing paradigms and requires new ways of thinking
about Web development. It is a Meta-Markup Language with a set of rules for creat-
ing semantic tags used to describe data.