Java is called a pure object oriented programming language. It was developed by Sun Microsystems in 1991. Java is partially based on C and C++ with more advanced features of object oriented model. Java programs are compiled and interpreted using JVM called Java Virtual Machine. One of the main features of Java is that, it is portable. Java is known as a very simple, portable, reliable and powerful programming language.
Java Features
The main purpose of development of Java Programming language was to develop a language that could provide a solution to the problems of modern programming. The purpose was to create a compact, simple and interactive language. Some of the main features of Java Programming Language are:
· Platform-Independent and Portable
· Robust and Secure
· Compiled and Interpreted
· Distributed
· Familiar, Simple and Small
· Multithreaded and Interactive
· High Performance
· Dynamic and Extensible
Java Development Kit
Java Development Kit contains a number of tools for the development and running of java programs. Tools in Java Development Kit includes:
· appletviewer: appletviewer is used to view the Java applets.
· javac: javac is used to compile a java program.
· java: java is used to interpret a java program.
· javap: javap is Java dissembler
· javah: javah is for creating HTML documents
· jdb: jdb is Java debugger
Difference between HTML and XML
HTMLHTML stands for Hypertext Markup Language. HTML standardizes the description of document layout and display, and is an integral part of every website today. In other words, HTML is a language for describing how pages of text, graphics and other information are organized, formatted and linked together.
Today, HTML pages are the standard interface to the internet. They can include animated graphics, sound and video, complete interactive programs, and good old-fashioned text. Millions of web pages are retrieved each day from thousands of web server computers around the world.
XML
XML stands for Extensible Markup Language. It is used to describe documents and data in a standardized, text-based format, easily transportable via standard internet protocols. XML, is based on the mother of all markup languages-Standard Generalized Markup Language(SGML). XML can be used to provide more details on the structure and meaning of the data pages rather than just specifying the format of the web pages. The formatting aspects can be specified separately, by using a formatting language such XSL(extended style sheet language). XML can describe data as records of data store or as a single document.
HTML vs. XML
As a language, XML defines both syntax and grammar rules. The rules are called Document Type Definition(DTD), and are one of the major differences between HTML and XML. XML uses metadata for describing data. The metadata of XML is not complex and adds to the readability of the document. XML, like HTML, also uses tags to describe data however, tags, unlike HTML, describes data and not how to present it. To display XML data,. You often transform it using XSLT into an HTML page.
HTML is comprised of a defined set of tags, XML on the other hand has very few defined gas. However, it does not mean that XML is powerless, the greatest power of XML is that it is extensible. You can create your own tags with your own semantic meaning. For example, you can create to use for your customer information data such as: Customer_First_Name like Manoj
This tag has meaning for you and, thus, to your application. This tag has been created by you to designate customer’s first name but its tells nothing about its presentation. But how is this gag useful to us? Consider now that data stream contains multiple customers information. If you want to find all customers with first name “Manoj” you can easily search for the "customer_first_name" tags. You can not perform such type of operation in HTML with the same ease and consistency, as HTML was bit designed for such purposes. XML is case sensitive while HTML is not.
Object Oriented Database
An object oriented database is used for complex databases. Such database applications require complex interrelationships among object hierarchies to be represented in database systems. These interrelationships are difficult to be implement in relational systems.Object oriented models represent complex systems very naturally through an inheritance hierarchy. Thus it is a very natural choice for such complex objects.
Consider a situation where you want to design a class, (let us say a Date class), the advantage of object oriented database management for such situations would be that they allow representation of not only the structure but also the operation on newer user defined database type such as finding the difference of two dates. Thus, object oriented database technologies are ideal for implementing such systems that support complex inherited objects, user defined data types (that require operations in addition to standard operation including the operations that support polymorphism).
Another major reason for the need of object oriented database system would be the seamless integration of this database technology with object-oriented applications. Software design is now, mostly based on object oriented technologies. Thus, object oriented database may provide a seamless interface for combining the two the technologies.
The object oriented databases are also required to manage complex, highly interrelated information. They provide solution in the most natural and easy way that is closer to our understanding of the system. Michael Brodie related the object oriented system to human conceptualization of a problem domain which enhances communication among the system designers, domain experts and the system end users.
The he concept of object oriented database was introduced in the late 1970s, however, it became significant only in the early 1980s. The initial commercial product offerings appeared in the late 1980s. Today, many object oriented databases products are available like Objectivity/DB (developed by Objectivity, Inc.), ONTOS DB (developed by ONTOS, Inc.), VERSANT (developed by Versant Object Technology Corp.) and ObjectStore (developed by Object Design, Inc.), GemStone (developed by Servio Corp.) and ObjectStore PSE Pro (developed by Object Design, Inc.) An object oriented database is presently being used for various applications in areas such as e-commerce, engineering product data management; and special purpose database in areas such as, securities and medicine.
