-- LathaMurugappan - 02 Nov 2008 XML provides an application independent way of sharing data. With a DTD, independent groups of people can agree to use a common DTD for interchanging data. Application can use a standard DTD to verify that data that you receive from the outside world is valid. You can also use a DTD to verify your own data.

The Difference Between XML and HTML XML is not a replacement for HTML. XML and HTML were designed with different goals: XML was designed to transport and store data, with focus on what data is. HTML was designed to display data, with focus on how data looks. HTML is about displaying information, while XML is about carrying information. Because of the lack of SGML support in mainstream Web browsers, most applications that deliver SGML information over the Web convert the SGML to HTML. This down-translation removes much of the intelligence of the original SGML information. That lost intelligence virtually eliminates information flexibility and poses a significant barrier to reuse, interchange, and automation. For this reason, XML (Extensible Markup Language) was developed by the XML working group (known as the SGML Editorial Review Board) formed under the auspices of the World Wide Web Consortium (W3C? ? ) in 1996. XML is a highly functional subset of SGML. The purpose of XML is to specify an SGML subset that works very well for delivering SGML information over the Web. When the mainstream Web browsers support XML, it is believed that it’s going to be very easy to publish SGML information on the Web. It's actually misnamed because XML is not a single Markup Language. It is a metalanguage to let users design their own markup language. XML is a public format and not a proprietary format of any company. The v 1.0 specifications was accepted by the W3C? ? as Recommendation on February 10, 1998. XML was conceived as a means of regaining the power and flexibility of SGML without most of its complexity. While retaining the beneficial features of SGML, XML removes many of the more complex features of SGML that make the authoring and design of suitable software both difficult and costly. But XML also lacks some important capabilities of SGML that primarily affect document creation, not document delivery. That’s because XML was not designed to replace SGML in every respect. The question that is open is not whether XML will succeed as a widespread data format, but rather how fast, to what level of success and with what products. The question of whether XML would enter the market was answered when Microsoft, Adobe, Netscape and other big market players not only supported the development of the new standard but began making sizable product investments to this new format. The leading Web browser Products already support XML in their latest releases. The momentum building behind the XML effort means that XML is inevitably destined to become the mainstream technology for powering broadly functional and highly valuable business applications on the Internet, intranets, and extranets

DTDs can check for: – correct document tree structure – correct lists of attributes – whether a specific element should belong in a given XML document at all • DTDs can also specify default values for attributes, and some value checking on attribute values. • DTDs do not: – perform type checking on element values – syntax checking on element values – handle extensible documents very well, where arbitrary elements can appear at places in the document

XML is a data structuring technology, used to design document formats for a wide range of uses. • XML is a language for creating other markup languages. – You can use XML to create a specific document format, such as HTML • XML is a markup language – Information about the data is embedded in the document with the data itself. – As a result, XML is self-describing. – This makes it well suited for data interchange. • XML is infrastructure – It is the core building block for a wide range of other technologies. • XML is verbose. Since XML is text-based, it is generally larger than the equivalent binary representation – Belief is text-based representations will age better than binary representations – Have at least a shred of a hope of deciphering the contents

XML Schemas are an area of XML syntax that is very similar in some ways to DTDs or Document Type Definitions; they govern, among other things, which elements should appear, and in which order, in your XML documents.he main differences between DTDs and Schemas are that XML Schemas are written in XML syntax and DTDs are not, and that Schemas are always external documents whereas DTDs can be internal or external. Aside from these two things, their purpose and function are fairly similar.

Reflexive Question 1: I do not feel too strange to abstract models like others students who are completely new to this kind of modeling.I have done a cousre UML patterns,where we deal with these kinds of model

2: If the design is not based on the user's need ,its not user freindly.Only if it according to the user,he/she can come back to the website.

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