Xml And Java Essays - Markup Languages, Technical Communication

Xml And Java Essays - Markup Languages, Technical Communication Xml And Java XML and Java Abstract Most web developers are intimately familiar with HTML, which is a language for presenting information on-screen so that it can be read by a human. A new markup language is rapidly gaining attention, however. XML allows for the presentation of information which can be read by a computer program. It is likely that the future of web development includes the creation of increasing numbers of programs, which make intelligent use of the data on XML-based web pages. And Java is a very good language for creating those programs. There has been a close relationship between Java and XML since the earliest mention of XML. John Bosak of Sun Microsystems, Chair of the XML Working Group has said that XML gives Java something to do (Web Techniques, pg. 43). Since there has been a decision to provide a standard Java API for manipulating XML (WT Pg. 43), the use of Java to manipulate XML documents is likely to continue, and increase over time. What is XML? XML stands for eXtensible Markup Language. It looks a lot like HTML. In fact, both HTML and XML are commonly viewed as a subset of SGML (Standard Generalized Markup Language). SGML is very complicated, a fact that has lead to its failure to gain widespread usage. HTML, its greatly simplified descendant, has been a resounding success, but it is beginning to demonstrate some significant limitations. XML is in between these markup languages in terms of complexity. It is more complex than HTML, but still significantly less complex than SGML. (Dynamic Web Publishing Unleashed - Pg. 744-745). It is essentially an attempt to define a common ground between HTML and SGML. Like SGML, XML is a metalanguage for defining markup languages. XML allows you to define your own markup language consisting of new tags which you can use to encode the information in your web documents far more precisely than can be done with HTML. XML is not a replacement for HTML. It is, instead, a supplement to HTML. While HTML will continue to be used for standard web pages, XML will be useful for applications that need more intelligent documents and more processing ability (DWP - Pg. 745). The main limitations of HTML are lack of extensibility, structure, and validation. (http:// metalab.unc.edu/pub/sun-info/standards/xml/why/xmlapps.html). Extensibility. HTML has a fixed number of tags. While the W3C and browser developers can (and frequently do) add tags, users cannot create their own tags to more accurately describe their data. Structure. HTML does not support the creation of nested tags, which would be used to describe and represent databases or object hierarchies. Validation. HTML does not support document validation. It has no means of allowing an application to check the data for validity, or to ensure that the markup is correct and well formed. XML differs from HTML in all three of these major areas: It allows developers to define new tags and attributes as needed It allows document tags to be nested as deeply as needed. Any XML document can include or make reference to a description of its grammar and syntax for use by applications that need to validate the structure of a document. XML will be most widely used in applications, which cannot be accomplished within the limitations of HTML. According to Jon Bosak of Sun Microsystems (Future of the web) These applications can be divided into four broad categories: Applications that require the Web client to mediate between two or more heterogeneous databases Applications that require the Web client to present different views of the same data to different users. Applications that require the Web client to present different views of the same data to different users. Applications in which intelligent Web agents attempt to tailor information discovery to the needs of the individual users. One more quote from Mr. Bosak: XML can do for data what Java has done for programs, which is to make the data both platform-independent and vendor-independent. Why Java? It can be argued that Java is an ideal language to use to create the applications listed above. At the most obvious level, both have been promoted almost exclusively for use in Web environments. But several features of the Java language make